merge with master and revert spec naming in k8sres

charts/postgres-operator/crds/operatorconfigurations.yaml

@@ -318,6 +318,47 @@ spec:
                   pattern: '^(\d+(e\d+)?|\d+(\.\d+)?(e\d+)?[EPTGMK]i?)$'
                 scalyr_server_url:
                   type: string
+            connection_pool:
+              type: object
+              properties:
+                connection_pool_schema:
+                  type: string
+                  #default: "pooler"
+                connection_pool_user:
+                  type: string
+                  #default: "pooler"
+                connection_pool_image:
+                  type: string
+                  #default: "registry.opensource.zalan.do/acid/pgbouncer"
+                connection_pool_max_db_connections:
+                  type: integer
+                  #default: 60
+                connection_pool_mode:
+                  type: string
+                  enum:
+                    - "session"
+                    - "transaction"
+                  #default: "transaction"
+                connection_pool_number_of_instances:
+                  type: integer
+                  minimum: 2
+                  #default: 2
+                connection_pool_default_cpu_limit:
+                  type: string
+                  pattern: '^(\d+m|\d+(\.\d{1,3})?)$'
+                  #default: "1"
+                connection_pool_default_cpu_request:
+                  type: string
+                  pattern: '^(\d+m|\d+(\.\d{1,3})?)$'
+                  #default: "500m"
+                connection_pool_default_memory_limit:
+                  type: string
+                  pattern: '^(\d+(e\d+)?|\d+(\.\d+)?(e\d+)?[EPTGMK]i?)$'
+                  #default: "100Mi"
+                connection_pool_default_memory_request:
+                  type: string
+                  pattern: '^(\d+(e\d+)?|\d+(\.\d+)?(e\d+)?[EPTGMK]i?)$'
+                  #default: "100Mi"
         status:
           type: object
           additionalProperties:

charts/postgres-operator/crds/postgresqls.yaml

@@ -106,6 +106,55 @@ spec:
                 uid:
                   format: uuid
                   type: string
+            connectionPool:
+              type: object
+              properties:
+                dockerImage:
+                  type: string
+                maxDBConnections:
+                  type: integer
+                mode:
+                  type: string
+                  enum:
+                    - "session"
+                    - "transaction"
+                numberOfInstances:
+                  type: integer
+                  minimum: 2
+                resources:
+                  type: object
+                  required:
+                    - requests
+                    - limits
+                  properties:
+                    limits:
+                      type: object
+                      required:
+                        - cpu
+                        - memory
+                      properties:
+                        cpu:
+                          type: string
+                          pattern: '^(\d+m|\d+(\.\d{1,3})?)$'
+                        memory:
+                          type: string
+                          pattern: '^(\d+(e\d+)?|\d+(\.\d+)?(e\d+)?[EPTGMK]i?)$'
+                    requests:
+                      type: object
+                      required:
+                        - cpu
+                        - memory
+                      properties:
+                        cpu:
+                          type: string
+                          pattern: '^(\d+m|\d+(\.\d{1,3})?)$'
+                        memory:
+                          type: string
+                          pattern: '^(\d+(e\d+)?|\d+(\.\d+)?(e\d+)?[EPTGMK]i?)$'
+                schema:
+                  type: string
+                user:
+                  type: string
             databases:
               type: object
               additionalProperties:
@@ -113,6 +162,8 @@ spec:
               # Note: usernames specified here as database owners must be declared in the users key of the spec key.
             dockerImage:
               type: string
+            enableConnectionPool:
+              type: boolean
             enableLogicalBackup:
               type: boolean
             enableMasterLoadBalancer:

charts/postgres-operator/templates/_helpers.tpl

@@ -31,6 +31,20 @@ Create a service account name.
 {{ default (include "postgres-operator.fullname" .) .Values.serviceAccount.name }}
 {{- end -}}
 
+{{/*
+Create a pod service account name.
+*/}}
+{{- define "postgres-pod.serviceAccountName" -}}
+{{ default (printf "%s-%v" (include "postgres-operator.fullname" .) "pod") .Values.podServiceAccount.name }}
+{{- end -}}
+
+{{/*
+Create a controller ID.
+*/}}
+{{- define "postgres-operator.controllerID" -}}
+{{ default (include "postgres-operator.fullname" .) .Values.controllerID.name }}
+{{- end -}}
+
 {{/*
 Create chart name and version as used by the chart label.
 */}}

charts/postgres-operator/templates/clusterrole-postgres-pod.yaml

@@ -2,7 +2,7 @@
 apiVersion: rbac.authorization.k8s.io/v1
 kind: ClusterRole
 metadata:
-  name: postgres-pod
+  name: {{ include "postgres-pod.serviceAccountName" . }}
   labels:
     app.kubernetes.io/name: {{ template "postgres-operator.name" . }}
     helm.sh/chart: {{ template "postgres-operator.chart" . }}

charts/postgres-operator/templates/clusterrole.yaml

@@ -128,6 +128,7 @@ rules:
   - apps
   resources:
   - statefulsets
+  - deployments
   verbs:
   - create
   - delete

charts/postgres-operator/templates/configmap.yaml

@@ -9,6 +9,7 @@ metadata:
     app.kubernetes.io/managed-by: {{ .Release.Service }}
     app.kubernetes.io/instance: {{ .Release.Name }}
 data:
+  pod_service_account_name: {{ include "postgres-pod.serviceAccountName" . }}
 {{ toYaml .Values.configGeneral | indent 2 }}
 {{ toYaml .Values.configUsers | indent 2 }}
 {{ toYaml .Values.configKubernetes | indent 2 }}
@@ -19,4 +20,5 @@ data:
 {{ toYaml .Values.configDebug | indent 2 }}
 {{ toYaml .Values.configLoggingRestApi | indent 2 }}
 {{ toYaml .Values.configTeamsApi | indent 2 }}
+{{ toYaml .Values.configConnectionPool | indent 2 }}
 {{- end }}

charts/postgres-operator/templates/deployment.yaml

@@ -43,6 +43,10 @@ spec:
       {{- else }}
         - name: POSTGRES_OPERATOR_CONFIGURATION_OBJECT
           value: {{ template "postgres-operator.fullname" . }}
+      {{- end }}
+      {{- if .Values.controllerID.create }}
+        - name: CONTROLLER_ID
+          value: {{ template "postgres-operator.controllerID" . }}
       {{- end }}
         resources:
 {{ toYaml .Values.resources | indent 10 }}

charts/postgres-operator/templates/operatorconfiguration.yaml

@@ -13,6 +13,7 @@ configuration:
   users:
 {{ toYaml .Values.configUsers | indent 4 }}
   kubernetes:
+    pod_service_account_name: {{ include "postgres-pod.serviceAccountName" . }}
     oauth_token_secret_name: {{ template "postgres-operator.fullname" . }}
 {{ toYaml .Values.configKubernetes | indent 4 }}
   postgres_pod_resources:
@@ -33,4 +34,6 @@ configuration:
 {{ toYaml .Values.configLoggingRestApi | indent 4 }}
   scalyr:
 {{ toYaml .Values.configScalyr | indent 4 }}
+  connection_pool:
+{{ toYaml .Values.configConnectionPool | indent 4 }}
 {{- end }}

charts/postgres-operator/values-crd.yaml

@@ -103,8 +103,6 @@ configKubernetes:
   # service account definition as JSON/YAML string to be used by postgres cluster pods
   # pod_service_account_definition: ""
 
-  # name of service account to be used by postgres cluster pods
-  pod_service_account_name: "postgres-pod"
   # role binding definition as JSON/YAML string to be used by pod service account
   # pod_service_account_role_binding_definition: ""
 
@@ -269,6 +267,25 @@ configScalyr:
   # Memory request value for the Scalyr sidecar
   scalyr_memory_request: 50Mi
 
+configConnectionPool:
+  # db schema to install lookup function into
+  connection_pool_schema: "pooler"
+  # db user for pooler to use
+  connection_pool_user: "pooler"
+  # docker image
+  connection_pool_image: "registry.opensource.zalan.do/acid/pgbouncer"
+  # max db connections the pooler should hold
+  connection_pool_max_db_connections: 60
+  # default pooling mode
+  connection_pool_mode: "transaction"
+  # number of pooler instances
+  connection_pool_number_of_instances: 2
+  # default resources
+  connection_pool_default_cpu_request: 500m
+  connection_pool_default_memory_request: 100Mi
+  connection_pool_default_cpu_limit: "1"
+  connection_pool_default_memory_limit: 100Mi
+
 rbac:
   # Specifies whether RBAC resources should be created
   create: true
@@ -284,6 +301,11 @@ serviceAccount:
   # If not set and create is true, a name is generated using the fullname template
   name:
 
+podServiceAccount:
+  # The name of the ServiceAccount to be used by postgres cluster pods
+  # If not set a name is generated using the fullname template and "-pod" suffix
+  name: "postgres-pod"
+
 priorityClassName: ""
 
 resources:
@@ -305,3 +327,12 @@ tolerations: []
 # Node labels for pod assignment
 # Ref: https://kubernetes.io/docs/user-guide/node-selection/
 nodeSelector: {}
+
+controllerID:
+  # Specifies whether a controller ID should be defined for the operator
+  # Note, all postgres manifest must then contain the following annotation to be found by this operator
+  # "acid.zalan.do/controller": <controller-ID-of-the-operator>
+  create: false
+  # The name of the controller ID to use.
+  # If not set and create is true, a name is generated using the fullname template
+  name:

charts/postgres-operator/values.yaml

@@ -96,8 +96,6 @@ configKubernetes:
   # service account definition as JSON/YAML string to be used by postgres cluster pods
   # pod_service_account_definition: ""
 
-  # name of service account to be used by postgres cluster pods
-  pod_service_account_name: "postgres-pod"
   # role binding definition as JSON/YAML string to be used by pod service account
   # pod_service_account_role_binding_definition: ""
 
@@ -245,6 +243,26 @@ configTeamsApi:
   # URL of the Teams API service
   # teams_api_url: http://fake-teams-api.default.svc.cluster.local
 
+# configure connection pooler deployment created by the operator
+configConnectionPool:
+  # db schema to install lookup function into
+  connection_pool_schema: "pooler"
+  # db user for pooler to use
+  connection_pool_user: "pooler"
+  # docker image
+  connection_pool_image: "registry.opensource.zalan.do/acid/pgbouncer"
+  # max db connections the pooler should hold
+  connection_pool_max_db_connections: 60
+  # default pooling mode
+  connection_pool_mode: "transaction"
+  # number of pooler instances
+  connection_pool_number_of_instances: 2
+  # default resources
+  connection_pool_default_cpu_request: 500m
+  connection_pool_default_memory_request: 100Mi
+  connection_pool_default_cpu_limit: "1"
+  connection_pool_default_memory_limit: 100Mi
+
 rbac:
   # Specifies whether RBAC resources should be created
   create: true
@@ -260,6 +278,11 @@ serviceAccount:
   # If not set and create is true, a name is generated using the fullname template
   name:
 
+podServiceAccount:
+  # The name of the ServiceAccount to be used by postgres cluster pods
+  # If not set a name is generated using the fullname template and "-pod" suffix
+  name: "postgres-pod"
+
 priorityClassName: ""
 
 resources:
@@ -281,3 +304,12 @@ tolerations: []
 # Node labels for pod assignment
 # Ref: https://kubernetes.io/docs/user-guide/node-selection/
 nodeSelector: {}
+
+controllerID:
+  # Specifies whether a controller ID should be defined for the operator
+  # Note, all postgres manifest must then contain the following annotation to be found by this operator
+  # "acid.zalan.do/controller": <controller-ID-of-the-operator>
+  create: false
+  # The name of the controller ID to use.
+  # If not set and create is true, a name is generated using the fullname template
+  name:

docker/DebugDockerfile

@@ -3,8 +3,17 @@ MAINTAINER Team ACID @ Zalando <team-acid@zalando.de>
 
 # We need root certificates to deal with teams api over https
 RUN apk --no-cache add ca-certificates go git musl-dev
-RUN go get github.com/derekparker/delve/cmd/dlv
 
 COPY build/* /
 
-CMD ["/root/go/bin/dlv", "--listen=:7777", "--headless=true", "--api-version=2", "exec", "/postgres-operator"]
+RUN addgroup -g 1000 pgo
+RUN adduser -D -u 1000 -G pgo -g 'Postgres Operator' pgo
+
+RUN go get github.com/derekparker/delve/cmd/dlv
+RUN cp /root/go/bin/dlv /dlv
+RUN chown -R pgo:pgo /dlv
+
+USER pgo:pgo
+RUN ls -l /
+
+CMD ["/dlv", "--listen=:7777", "--headless=true", "--api-version=2", "exec", "/postgres-operator"]

docs/reference/cluster_manifest.md

@@ -140,6 +140,11 @@ These parameters are grouped directly under  the `spec` key in the manifest.
   is `false`, then no volume will be mounted no matter how operator was
   configured (so you can override the operator configuration). Optional.
 
+* **enableConnectionPool**
+  Tells the operator to create a connection pool with a database. If this
+  field is true, a connection pool deployment will be created even if
+  `connectionPool` section is empty. Optional, not set by default.
+
 * **enableLogicalBackup**
   Determines if the logical backup of this cluster should be taken and uploaded
   to S3. Default: false. Optional.
@@ -184,7 +189,7 @@ explanation of `ttl` and `loop_wait` parameters.
   ```
   hostssl all +pamrole all pam
   ```
-  , where pamrole is the name of the role for the pam authentication; any
+  where pamrole is the name of the role for the pam authentication; any
   custom `pg_hba` should include the pam line to avoid breaking pam
   authentication. Optional.
 
@@ -360,6 +365,35 @@ CPU and memory limits for the sidecar container.
   memory limits for the sidecar container. Optional, overrides the
   `default_memory_limits` operator configuration parameter. Optional.
 
+## Connection pool
+
+Parameters are grouped under the `connectionPool` top-level key and specify
+configuration for connection pool. If this section is not empty, a connection
+pool will be created for a database even if `enableConnectionPool` is not
+present.
+
+* **numberOfInstances**
+  How many instances of connection pool to create.
+
+* **schema**
+  Schema to create for credentials lookup function.
+
+* **user**
+  User to create for connection pool to be able to connect to a database.
+
+* **dockerImage**
+  Which docker image to use for connection pool deployment.
+
+* **maxDBConnections**
+  How many connections the pooler can max hold. This value is divided among the
+  pooler pods.
+
+* **mode**
+  In which mode to run connection pool, transaction or session.
+
+* **resources**
+  Resource configuration for connection pool deployment.
+
 ## Custom TLS certificates
 
 Those parameters are grouped under the `tls` top-level key.
@@ -379,4 +413,4 @@ Those parameters are grouped under the `tls` top-level key.
 
 * **caFile**
   Optional filename to the CA certificate. Useful when the client connects
-  with `sslmode=verify-ca` or `sslmode=verify-full`.
+  with `sslmode=verify-ca` or `sslmode=verify-full`. Default is empty.

docs/reference/operator_parameters.md

@@ -596,3 +596,40 @@ scalyr sidecar. In the CRD-based configuration they are grouped under the
 
 * **scalyr_memory_limit**
   Memory limit value for the Scalyr sidecar. The default is `500Mi`.
+
+## Connection pool configuration
+
+Parameters are grouped under the `connection_pool` top-level key and specify
+default configuration for connection pool, if a postgres manifest requests it
+but do not specify some of the parameters. All of them are optional with the
+operator being able to provide some reasonable defaults.
+
+* **connection_pool_number_of_instances**
+  How many instances of connection pool to create. Default is 2 which is also
+  the required minimum.
+
+* **connection_pool_schema**
+  Schema to create for credentials lookup function. Default is `pooler`.
+
+* **connection_pool_user**
+  User to create for connection pool to be able to connect to a database.
+  Default is `pooler`.
+
+* **connection_pool_image**
+  Docker image to use for connection pool deployment.
+  Default: "registry.opensource.zalan.do/acid/pgbouncer"
+
+* **connection_pool_max_db_connections**
+  How many connections the pooler can max hold. This value is divided among the
+  pooler pods. Default is 60 which will make up 30 connections per pod for the
+  default setup with two instances.
+
+* **connection_pool_mode**
+  Default pool mode, `session` or `transaction`. Default is `transaction`.
+
+* **connection_pool_default_cpu_request**
+  **connection_pool_default_memory_reques**
+  **connection_pool_default_cpu_limit**
+  **connection_pool_default_memory_limit**
+  Default resource configuration for connection pool deployment. The internal
+  default for memory request and limit is `100Mi`, for CPU it is `500m` and `1`.

docs/user.md

@@ -30,7 +30,7 @@ spec:
   databases:
     foo: zalando
   postgresql:
-    version: "11"
+    version: "12"
 ```
 
 Once you cloned the Postgres Operator [repository](https://github.com/zalando/postgres-operator)
@@ -512,12 +512,65 @@ monitoring is outside the scope of operator responsibilities. See
 [administrator documentation](administrator.md) for details on how backups are
 executed.
 
+## Connection pool
+
+The operator can create a database side connection pool for those applications,
+where an application side pool is not feasible, but a number of connections is
+high. To create a connection pool together with a database, modify the
+manifest:
+
+```yaml
+spec:
+  enableConnectionPool: true
+```
+
+This will tell the operator to create a connection pool with default
+configuration, through which one can access the master via a separate service
+`{cluster-name}-pooler`. In most of the cases provided default configuration
+should be good enough.
+
+To configure a new connection pool, specify:
+
+```
+spec:
+  connectionPool:
+    # how many instances of connection pool to create
+    number_of_instances: 2
+
+    # in which mode to run, session or transaction
+    mode: "transaction"
+
+    # schema, which operator will create to install credentials lookup
+    # function
+    schema: "pooler"
+
+    # user, which operator will create for connection pool
+    user: "pooler"
+
+    # resources for each instance
+    resources:
+      requests:
+        cpu: 500m
+        memory: 100Mi
+      limits:
+        cpu: "1"
+        memory: 100Mi
+```
+
+By default `pgbouncer` is used to create a connection pool. To find out about
+pool modes see [docs](https://www.pgbouncer.org/config.html#pool_mode) (but it
+should be general approach between different implementation).
+
+Note, that using `pgbouncer` means meaningful resource CPU limit should be less
+than 1 core (there is a way to utilize more than one, but in K8S it's easier
+just to spin up more instances).
+
 ## Custom TLS certificates
 
 By default, the spilo image generates its own TLS certificate during startup.
-This certificate is not secure since it cannot be verified and thus doesn't
-protect from active MITM attacks. In this section we show how a Kubernete
-Secret resources can be loaded with a custom TLS certificate.
+However, this certificate cannot be verified and thus doesn't protect from
+active MITM attacks. In this section we show how to specify a custom TLS
+certificate which is mounted in the database pods via a K8s Secret.
 
 Before applying these changes, the operator must also be configured with the
 `spilo_fsgroup` set to the GID matching the postgres user group. If the value

e2e/tests/test_e2e.py

@@ -9,6 +9,10 @@ import yaml
 from kubernetes import client, config
 
 
+def to_selector(labels):
+    return ",".join(["=".join(l) for l in labels.items()])
+
+
 class EndToEndTestCase(unittest.TestCase):
     '''
     Test interaction of the operator with multiple K8s components.
@@ -47,7 +51,8 @@ class EndToEndTestCase(unittest.TestCase):
         for filename in ["operator-service-account-rbac.yaml",
                          "configmap.yaml",
                          "postgres-operator.yaml"]:
-            k8s.create_with_kubectl("manifests/" + filename)
+            result = k8s.create_with_kubectl("manifests/" + filename)
+            print("stdout: {}, stderr: {}".format(result.stdout, result.stderr))
 
         k8s.wait_for_operator_pod_start()
 
@@ -55,9 +60,14 @@ class EndToEndTestCase(unittest.TestCase):
             'default', label_selector='name=postgres-operator').items[0].spec.containers[0].image
         print("Tested operator image: {}".format(actual_operator_image))  # shows up after tests finish
 
-        k8s.create_with_kubectl("manifests/minimal-postgres-manifest.yaml")
+        result = k8s.create_with_kubectl("manifests/minimal-postgres-manifest.yaml")
+        print('stdout: {}, stderr: {}'.format(result.stdout, result.stderr))
+        try:
             k8s.wait_for_pod_start('spilo-role=master')
             k8s.wait_for_pod_start('spilo-role=replica')
+        except timeout_decorator.TimeoutError:
+            print('Operator log: {}'.format(k8s.get_operator_log()))
+            raise
 
     @timeout_decorator.timeout(TEST_TIMEOUT_SEC)
     def test_enable_load_balancer(self):
@@ -66,7 +76,7 @@ class EndToEndTestCase(unittest.TestCase):
         '''
 
         k8s = self.k8s
-        cluster_label = 'cluster-name=acid-minimal-cluster'
+        cluster_label = 'application=spilo,cluster-name=acid-minimal-cluster'
 
         # enable load balancer services
         pg_patch_enable_lbs = {
@@ -178,7 +188,7 @@ class EndToEndTestCase(unittest.TestCase):
         Lower resource limits below configured minimum and let operator fix it
         '''
         k8s = self.k8s
-        cluster_label = 'cluster-name=acid-minimal-cluster'
+        cluster_label = 'application=spilo,cluster-name=acid-minimal-cluster'
         labels = 'spilo-role=master,' + cluster_label
         _, failover_targets = k8s.get_pg_nodes(cluster_label)
 
@@ -247,7 +257,7 @@ class EndToEndTestCase(unittest.TestCase):
            Remove node readiness label from master node. This must cause a failover.
         '''
         k8s = self.k8s
-        cluster_label = 'cluster-name=acid-minimal-cluster'
+        cluster_label = 'application=spilo,cluster-name=acid-minimal-cluster'
         labels = 'spilo-role=master,' + cluster_label
         readiness_label = 'lifecycle-status'
         readiness_value = 'ready'
@@ -289,7 +299,7 @@ class EndToEndTestCase(unittest.TestCase):
            Scale up from 2 to 3 and back to 2 pods by updating the Postgres manifest at runtime.
         '''
         k8s = self.k8s
-        labels = "cluster-name=acid-minimal-cluster"
+        labels = "application=spilo,cluster-name=acid-minimal-cluster"
 
         k8s.wait_for_pg_to_scale(3)
         self.assertEqual(3, k8s.count_pods_with_label(labels))
@@ -339,13 +349,99 @@ class EndToEndTestCase(unittest.TestCase):
         }
         k8s.update_config(unpatch_custom_service_annotations)
 
+    @timeout_decorator.timeout(TEST_TIMEOUT_SEC)
+    def test_enable_disable_connection_pool(self):
+        '''
+        For a database without connection pool, then turns it on, scale up,
+        turn off and on again. Test with different ways of doing this (via
+        enableConnectionPool or connectionPool configuration section). At the
+        end turn the connection pool off to not interfere with other tests.
+        '''
+        k8s = self.k8s
+        service_labels = {
+            'cluster-name': 'acid-minimal-cluster',
+        }
+        pod_labels = dict({
+            'connection-pool': 'acid-minimal-cluster-pooler',
+        })
+
+        pod_selector = to_selector(pod_labels)
+        service_selector = to_selector(service_labels)
+
+        try:
+            # enable connection pool
+            k8s.api.custom_objects_api.patch_namespaced_custom_object(
+                'acid.zalan.do', 'v1', 'default',
+                'postgresqls', 'acid-minimal-cluster',
+                {
+                    'spec': {
+                        'enableConnectionPool': True,
+                    }
+                })
+            k8s.wait_for_pod_start(pod_selector)
+
+            pods = k8s.api.core_v1.list_namespaced_pod(
+                'default', label_selector=pod_selector
+            ).items
+
+            self.assertTrue(pods, 'No connection pool pods')
+
+            k8s.wait_for_service(service_selector)
+            services = k8s.api.core_v1.list_namespaced_service(
+                'default', label_selector=service_selector
+            ).items
+            services = [
+                s for s in services
+                if s.metadata.name.endswith('pooler')
+            ]
+
+            self.assertTrue(services, 'No connection pool service')
+
+            # scale up connection pool deployment
+            k8s.api.custom_objects_api.patch_namespaced_custom_object(
+                'acid.zalan.do', 'v1', 'default',
+                'postgresqls', 'acid-minimal-cluster',
+                {
+                    'spec': {
+                        'connectionPool': {
+                            'numberOfInstances': 2,
+                        },
+                    }
+                })
+
+            k8s.wait_for_running_pods(pod_selector, 2)
+
+            # turn it off, keeping configuration section
+            k8s.api.custom_objects_api.patch_namespaced_custom_object(
+                'acid.zalan.do', 'v1', 'default',
+                'postgresqls', 'acid-minimal-cluster',
+                {
+                    'spec': {
+                        'enableConnectionPool': False,
+                    }
+                })
+            k8s.wait_for_pods_to_stop(pod_selector)
+
+            k8s.api.custom_objects_api.patch_namespaced_custom_object(
+                'acid.zalan.do', 'v1', 'default',
+                'postgresqls', 'acid-minimal-cluster',
+                {
+                    'spec': {
+                        'enableConnectionPool': True,
+                    }
+                })
+            k8s.wait_for_pod_start(pod_selector)
+        except timeout_decorator.TimeoutError:
+            print('Operator log: {}'.format(k8s.get_operator_log()))
+            raise
+
     @timeout_decorator.timeout(TEST_TIMEOUT_SEC)
     def test_taint_based_eviction(self):
         '''
            Add taint "postgres=:NoExecute" to node with master. This must cause a failover.
         '''
         k8s = self.k8s
-        cluster_label = 'cluster-name=acid-minimal-cluster'
+        cluster_label = 'application=spilo,cluster-name=acid-minimal-cluster'
 
         # get nodes of master and replica(s) (expected target of new master)
         current_master_node, current_replica_nodes = k8s.get_pg_nodes(cluster_label)
@@ -473,7 +569,7 @@ class K8s:
     Wraps around K8 api client and helper methods.
     '''
 
-    RETRY_TIMEOUT_SEC = 5
+    RETRY_TIMEOUT_SEC = 10
 
     def __init__(self):
         self.api = K8sApi()
@@ -496,12 +592,39 @@ class K8s:
         # for local execution ~ 10 seconds suffices
         time.sleep(60)
 
+    def get_operator_pod(self):
+        pods = self.api.core_v1.list_namespaced_pod(
+            'default', label_selector='name=postgres-operator'
+        ).items
+
+        if pods:
+            return pods[0]
+
+        return None
+
+    def get_operator_log(self):
+        operator_pod = self.get_operator_pod()
+        pod_name = operator_pod.metadata.name
+        return self.api.core_v1.read_namespaced_pod_log(
+            name=pod_name,
+            namespace='default'
+        )
+
     def wait_for_pod_start(self, pod_labels, namespace='default'):
         pod_phase = 'No pod running'
         while pod_phase != 'Running':
             pods = self.api.core_v1.list_namespaced_pod(namespace, label_selector=pod_labels).items
             if pods:
                 pod_phase = pods[0].status.phase
+
+            if pods and pod_phase != 'Running':
+                pod_name = pods[0].metadata.name
+                response = self.api.core_v1.read_namespaced_pod(
+                    name=pod_name,
+                    namespace=namespace
+                )
+                print("Pod description {}".format(response))
+
             time.sleep(self.RETRY_TIMEOUT_SEC)
 
     def get_service_type(self, svc_labels, namespace='default'):
@@ -531,10 +654,27 @@ class K8s:
         _ = self.api.custom_objects_api.patch_namespaced_custom_object(
             "acid.zalan.do", "v1", namespace, "postgresqls", "acid-minimal-cluster", body)
 
-        labels = 'cluster-name=acid-minimal-cluster'
+        labels = 'application=spilo,cluster-name=acid-minimal-cluster'
         while self.count_pods_with_label(labels) != number_of_instances:
             time.sleep(self.RETRY_TIMEOUT_SEC)
 
+    def wait_for_running_pods(self, labels, number, namespace=''):
+        while self.count_pods_with_label(labels) != number:
+            time.sleep(self.RETRY_TIMEOUT_SEC)
+
+    def wait_for_pods_to_stop(self, labels, namespace=''):
+        while self.count_pods_with_label(labels) != 0:
+            time.sleep(self.RETRY_TIMEOUT_SEC)
+
+    def wait_for_service(self, labels, namespace='default'):
+        def get_services():
+            return self.api.core_v1.list_namespaced_service(
+                namespace, label_selector=labels
+            ).items
+
+        while not get_services():
+            time.sleep(self.RETRY_TIMEOUT_SEC)
+
     def count_pods_with_label(self, labels, namespace='default'):
         return len(self.api.core_v1.list_namespaced_pod(namespace, label_selector=labels).items)
 
@@ -571,7 +711,10 @@ class K8s:
         self.wait_for_operator_pod_start()
 
     def create_with_kubectl(self, path):
-        subprocess.run(["kubectl", "create", "-f", path])
+        return subprocess.run(
+            ["kubectl", "create", "-f", path],
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE)
 
 
 if __name__ == '__main__':

manifests/complete-postgres-manifest.yaml

@@ -24,7 +24,7 @@ spec:
   databases:
     foo: zalando
   postgresql:
-    version: "11"
+    version: "12"
     parameters: # Expert section
       shared_buffers: "32MB"
       max_connections: "10"

manifests/configmap.yaml

@@ -11,6 +11,16 @@ data:
   cluster_history_entries: "1000"
   cluster_labels: application:spilo
   cluster_name_label: cluster-name
+  # connection_pool_default_cpu_limit: "1"
+  # connection_pool_default_cpu_request: "500m"
+  # connection_pool_default_memory_limit: 100Mi
+  # connection_pool_default_memory_request: 100Mi
+  connection_pool_image: "registry.opensource.zalan.do/acid/pgbouncer:master-5"
+  # connection_pool_max_db_connections: 60
+  # connection_pool_mode: "transaction"
+  # connection_pool_number_of_instances: 2
+  # connection_pool_schema: "pooler"
+  # connection_pool_user: "pooler"
   # custom_service_annotations: "keyx:valuez,keya:valuea"
   # custom_pod_annotations: "keya:valuea,keyb:valueb"
   db_hosted_zone: db.example.com

manifests/minimal-postgres-manifest.yaml

@@ -16,4 +16,4 @@ spec:
   databases:
     foo: zalando  # dbname: owner
   postgresql:
-    version: "11"
+    version: "12"

manifests/operator-service-account-rbac.yaml

@@ -129,6 +129,7 @@ rules:
   - apps
   resources:
   - statefulsets
+  - deployments
   verbs:
   - create
   - delete

manifests/operatorconfiguration.crd.yaml

@@ -294,6 +294,47 @@ spec:
                   pattern: '^(\d+(e\d+)?|\d+(\.\d+)?(e\d+)?[EPTGMK]i?)$'
                 scalyr_server_url:
                   type: string
+            connection_pool:
+              type: object
+              properties:
+                connection_pool_schema:
+                  type: string
+                  #default: "pooler"
+                connection_pool_user:
+                  type: string
+                  #default: "pooler"
+                connection_pool_image:
+                  type: string
+                  #default: "registry.opensource.zalan.do/acid/pgbouncer"
+                connection_pool_max_db_connections:
+                  type: integer
+                  #default: 60
+                connection_pool_mode:
+                  type: string
+                  enum:
+                    - "session"
+                    - "transaction"
+                  #default: "transaction"
+                connection_pool_number_of_instances:
+                  type: integer
+                  minimum: 2
+                  #default: 2
+                connection_pool_default_cpu_limit:
+                  type: string
+                  pattern: '^(\d+m|\d+(\.\d{1,3})?)$'
+                  #default: "1"
+                connection_pool_default_cpu_request:
+                  type: string
+                  pattern: '^(\d+m|\d+(\.\d{1,3})?)$'
+                  #default: "500m"
+                connection_pool_default_memory_limit:
+                  type: string
+                  pattern: '^(\d+(e\d+)?|\d+(\.\d+)?(e\d+)?[EPTGMK]i?)$'
+                  #default: "100Mi"
+                connection_pool_default_memory_request:
+                  type: string
+                  pattern: '^(\d+(e\d+)?|\d+(\.\d+)?(e\d+)?[EPTGMK]i?)$'
+                  #default: "100Mi"
         status:
           type: object
           additionalProperties:

manifests/postgresql-operator-default-configuration.yaml

@@ -121,3 +121,14 @@ configuration:
     scalyr_memory_limit: 500Mi
     scalyr_memory_request: 50Mi
     # scalyr_server_url: ""
+  connection_pool:
+    connection_pool_default_cpu_limit: "1"
+    connection_pool_default_cpu_request: "500m"
+    connection_pool_default_memory_limit: 100Mi
+    connection_pool_default_memory_request: 100Mi
+    connection_pool_image: "registry.opensource.zalan.do/acid/pgbouncer:master-5"
+    # connection_pool_max_db_connections: 60
+    connection_pool_mode: "transaction"
+    connection_pool_number_of_instances: 2
+    # connection_pool_schema: "pooler"
+    # connection_pool_user: "pooler"

manifests/postgresql.crd.yaml

@@ -70,6 +70,55 @@ spec:
                 uid:
                   format: uuid
                   type: string
+            connectionPool:
+              type: object
+              properties:
+                dockerImage:
+                  type: string
+                maxDBConnections:
+                  type: integer
+                mode:
+                  type: string
+                  enum:
+                    - "session"
+                    - "transaction"
+                numberOfInstances:
+                  type: integer
+                  minimum: 2
+                resources:
+                  type: object
+                  required:
+                    - requests
+                    - limits
+                  properties:
+                    limits:
+                      type: object
+                      required:
+                        - cpu
+                        - memory
+                      properties:
+                        cpu:
+                          type: string
+                          pattern: '^(\d+m|\d+(\.\d{1,3})?)$'
+                        memory:
+                          type: string
+                          pattern: '^(\d+(e\d+)?|\d+(\.\d+)?(e\d+)?[EPTGMK]i?)$'
+                    requests:
+                      type: object
+                      required:
+                        - cpu
+                        - memory
+                      properties:
+                        cpu:
+                          type: string
+                          pattern: '^(\d+m|\d+(\.\d{1,3})?)$'
+                        memory:
+                          type: string
+                          pattern: '^(\d+(e\d+)?|\d+(\.\d+)?(e\d+)?[EPTGMK]i?)$'
+                schema:
+                  type: string
+                user:
+                  type: string
             databases:
               type: object
               additionalProperties:
@@ -77,6 +126,8 @@ spec:
               # Note: usernames specified here as database owners must be declared in the users key of the spec key.
             dockerImage:
               type: string
+            enableConnectionPool:
+              type: boolean
             enableLogicalBackup:
               type: boolean
             enableMasterLoadBalancer:

manifests/standby-manifest.yaml

@@ -9,7 +9,7 @@ spec:
     size: 1Gi
   numberOfInstances: 1
   postgresql:
-    version: "11"
+    version: "12"
 # Make this a standby cluster and provide the s3 bucket path of source cluster for continuous streaming.
   standby:
     s3_wal_path: "s3://path/to/bucket/containing/wal/of/source/cluster/"

pkg/apis/acid.zalan.do/v1/crds.go

@@ -105,6 +105,7 @@ var OperatorConfigCRDResourceColumns = []apiextv1beta1.CustomResourceColumnDefin
 
 var min0 = 0.0
 var min1 = 1.0
+var min2 = 2.0
 var minDisable = -1.0
 
 // PostgresCRDResourceValidation to check applied manifest parameters
@@ -176,6 +177,76 @@ var PostgresCRDResourceValidation = apiextv1beta1.CustomResourceValidation{
 							},
 						},
 					},
+					"connectionPool": {
+						Type: "object",
+						Properties: map[string]apiextv1beta1.JSONSchemaProps{
+							"dockerImage": {
+								Type: "string",
+							},
+							"maxDBConnections": {
+								Type: "integer",
+							},
+							"mode": {
+								Type: "string",
+								Enum: []apiextv1beta1.JSON{
+									{
+										Raw: []byte(`"session"`),
+									},
+									{
+										Raw: []byte(`"transaction"`),
+									},
+								},
+							},
+							"numberOfInstances": {
+								Type:    "integer",
+								Minimum: &min2,
+							},
+							"resources": {
+								Type:     "object",
+								Required: []string{"requests", "limits"},
+								Properties: map[string]apiextv1beta1.JSONSchemaProps{
+									"limits": {
+										Type:     "object",
+										Required: []string{"cpu", "memory"},
+										Properties: map[string]apiextv1beta1.JSONSchemaProps{
+											"cpu": {
+												Type:        "string",
+												Description: "Decimal natural followed by m, or decimal natural followed by dot followed by up to three decimal digits (precision used by Kubernetes). Must be greater than 0",
+												Pattern:     "^(\\d+m|\\d+(\\.\\d{1,3})?)$",
+											},
+											"memory": {
+												Type:        "string",
+												Description: "Plain integer or fixed-point integer using one of these suffixes: E, P, T, G, M, k (with or without a tailing i). Must be greater than 0",
+												Pattern:     "^(\\d+(e\\d+)?|\\d+(\\.\\d+)?(e\\d+)?[EPTGMK]i?)$",
+											},
+										},
+									},
+									"requests": {
+										Type:     "object",
+										Required: []string{"cpu", "memory"},
+										Properties: map[string]apiextv1beta1.JSONSchemaProps{
+											"cpu": {
+												Type:        "string",
+												Description: "Decimal natural followed by m, or decimal natural followed by dot followed by up to three decimal digits (precision used by Kubernetes). Must be greater than 0",
+												Pattern:     "^(\\d+m|\\d+(\\.\\d{1,3})?)$",
+											},
+											"memory": {
+												Type:        "string",
+												Description: "Plain integer or fixed-point integer using one of these suffixes: E, P, T, G, M, k (with or without a tailing i). Must be greater than 0",
+												Pattern:     "^(\\d+(e\\d+)?|\\d+(\\.\\d+)?(e\\d+)?[EPTGMK]i?)$",
+											},
+										},
+									},
+								},
+							},
+							"schema": {
+								Type: "string",
+							},
+							"user": {
+								Type: "string",
+							},
+						},
+					},
 					"databases": {
 						Type: "object",
 						AdditionalProperties: &apiextv1beta1.JSONSchemaPropsOrBool{
@@ -188,6 +259,9 @@ var PostgresCRDResourceValidation = apiextv1beta1.CustomResourceValidation{
 					"dockerImage": {
 						Type: "string",
 					},
+					"enableConnectionPool": {
+						Type: "boolean",
+					},
 					"enableLogicalBackup": {
 						Type: "boolean",
 					},
@@ -1055,6 +1129,54 @@ var OperatorConfigCRDResourceValidation = apiextv1beta1.CustomResourceValidation
 							},
 						},
 					},
+					"connection_pool": {
+						Type: "object",
+						Properties: map[string]apiextv1beta1.JSONSchemaProps{
+							"connection_pool_default_cpu_limit": {
+								Type:    "string",
+								Pattern: "^(\\d+m|\\d+(\\.\\d{1,3})?)$",
+							},
+							"connection_pool_default_cpu_request": {
+								Type:    "string",
+								Pattern: "^(\\d+m|\\d+(\\.\\d{1,3})?)$",
+							},
+							"connection_pool_default_memory_limit": {
+								Type:    "string",
+								Pattern: "^(\\d+(e\\d+)?|\\d+(\\.\\d+)?(e\\d+)?[EPTGMK]i?)$",
+							},
+							"connection_pool_default_memory_request": {
+								Type:    "string",
+								Pattern: "^(\\d+(e\\d+)?|\\d+(\\.\\d+)?(e\\d+)?[EPTGMK]i?)$",
+							},
+							"connection_pool_image": {
+								Type: "string",
+							},
+							"connection_pool_max_db_connections": {
+								Type: "integer",
+							},
+							"connection_pool_mode": {
+								Type: "string",
+								Enum: []apiextv1beta1.JSON{
+									{
+										Raw: []byte(`"session"`),
+									},
+									{
+										Raw: []byte(`"transaction"`),
+									},
+								},
+							},
+							"connection_pool_number_of_instances": {
+								Type:    "integer",
+								Minimum: &min2,
+							},
+							"connection_pool_schema": {
+								Type: "string",
+							},
+							"connection_pool_user": {
+								Type: "string",
+							},
+						},
+					},
 				},
 			},
 			"status": {

pkg/apis/acid.zalan.do/v1/operator_configuration_type.go

@@ -1,5 +1,7 @@
 package v1
 
+// Operator configuration CRD definition, please use snake_case for field names.
+
 import (
 	"github.com/zalando/postgres-operator/pkg/util/config"
 
@@ -151,6 +153,20 @@ type ScalyrConfiguration struct {
 	ScalyrMemoryLimit   string `json:"scalyr_memory_limit,omitempty"`
 }
 
+// Defines default configuration for connection pool
+type ConnectionPoolConfiguration struct {
+	NumberOfInstances    *int32 `json:"connection_pool_number_of_instances,omitempty"`
+	Schema               string `json:"connection_pool_schema,omitempty"`
+	User                 string `json:"connection_pool_user,omitempty"`
+	Image                string `json:"connection_pool_image,omitempty"`
+	Mode                 string `json:"connection_pool_mode,omitempty"`
+	MaxDBConnections     *int32 `json:"connection_pool_max_db_connections,omitempty"`
+	DefaultCPURequest    string `json:"connection_pool_default_cpu_request,omitempty"`
+	DefaultMemoryRequest string `json:"connection_pool_default_memory_request,omitempty"`
+	DefaultCPULimit      string `json:"connection_pool_default_cpu_limit,omitempty"`
+	DefaultMemoryLimit   string `json:"connection_pool_default_memory_limit,omitempty"`
+}
+
 // OperatorLogicalBackupConfiguration defines configuration for logical backup
 type OperatorLogicalBackupConfiguration struct {
 	Schedule          string `json:"logical_backup_schedule,omitempty"`
@@ -187,6 +203,7 @@ type OperatorConfigurationData struct {
 	LoggingRESTAPI             LoggingRESTAPIConfiguration        `json:"logging_rest_api"`
 	Scalyr                     ScalyrConfiguration                `json:"scalyr"`
 	LogicalBackup              OperatorLogicalBackupConfiguration `json:"logical_backup"`
+	ConnectionPool             ConnectionPoolConfiguration        `json:"connection_pool"`
 }
 
 //Duration shortens this frequently used name

pkg/apis/acid.zalan.do/v1/postgresql_type.go

@@ -1,5 +1,7 @@
 package v1
 
+// Postgres CRD definition, please use CamelCase for field names.
+
 import (
 	"time"
 
@@ -27,6 +29,9 @@ type PostgresSpec struct {
 	Patroni         `json:"patroni,omitempty"`
 	Resources       `json:"resources,omitempty"`
 
+	EnableConnectionPool *bool           `json:"enableConnectionPool,omitempty"`
+	ConnectionPool       *ConnectionPool `json:"connectionPool,omitempty"`
+
 	TeamID      string `json:"teamId"`
 	DockerImage string `json:"dockerImage,omitempty"`
 
@@ -162,3 +167,24 @@ type UserFlags []string
 type PostgresStatus struct {
 	PostgresClusterStatus string `json:"PostgresClusterStatus"`
 }
+
+// Options for connection pooler
+//
+// TODO: prepared snippets of configuration, one can choose via type, e.g.
+// pgbouncer-large (with higher resources) or odyssey-small (with smaller
+// resources)
+// Type              string `json:"type,omitempty"`
+//
+// TODO: figure out what other important parameters of the connection pool it
+// makes sense to expose. E.g. pool size (min/max boundaries), max client
+// connections etc.
+type ConnectionPool struct {
+	NumberOfInstances *int32 `json:"numberOfInstances,omitempty"`
+	Schema            string `json:"schema,omitempty"`
+	User              string `json:"user,omitempty"`
+	Mode              string `json:"mode,omitempty"`
+	DockerImage       string `json:"dockerImage,omitempty"`
+	MaxDBConnections  *int32 `json:"maxDBConnections,omitempty"`
+
+	Resources `json:"resources,omitempty"`
+}

pkg/apis/acid.zalan.do/v1/zz_generated.deepcopy.go

@@ -68,6 +68,59 @@ func (in *CloneDescription) DeepCopy() *CloneDescription {
 	return out
 }
 
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *ConnectionPool) DeepCopyInto(out *ConnectionPool) {
+	*out = *in
+	if in.NumberOfInstances != nil {
+		in, out := &in.NumberOfInstances, &out.NumberOfInstances
+		*out = new(int32)
+		**out = **in
+	}
+	if in.MaxDBConnections != nil {
+		in, out := &in.MaxDBConnections, &out.MaxDBConnections
+		*out = new(int32)
+		**out = **in
+	}
+	out.Resources = in.Resources
+	return
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new ConnectionPool.
+func (in *ConnectionPool) DeepCopy() *ConnectionPool {
+	if in == nil {
+		return nil
+	}
+	out := new(ConnectionPool)
+	in.DeepCopyInto(out)
+	return out
+}
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *ConnectionPoolConfiguration) DeepCopyInto(out *ConnectionPoolConfiguration) {
+	*out = *in
+	if in.NumberOfInstances != nil {
+		in, out := &in.NumberOfInstances, &out.NumberOfInstances
+		*out = new(int32)
+		**out = **in
+	}
+	if in.MaxDBConnections != nil {
+		in, out := &in.MaxDBConnections, &out.MaxDBConnections
+		*out = new(int32)
+		**out = **in
+	}
+	return
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new ConnectionPoolConfiguration.
+func (in *ConnectionPoolConfiguration) DeepCopy() *ConnectionPoolConfiguration {
+	if in == nil {
+		return nil
+	}
+	out := new(ConnectionPoolConfiguration)
+	in.DeepCopyInto(out)
+	return out
+}
+
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *KubernetesMetaConfiguration) DeepCopyInto(out *KubernetesMetaConfiguration) {
 	*out = *in
@@ -255,6 +308,7 @@ func (in *OperatorConfigurationData) DeepCopyInto(out *OperatorConfigurationData
 	out.LoggingRESTAPI = in.LoggingRESTAPI
 	out.Scalyr = in.Scalyr
 	out.LogicalBackup = in.LogicalBackup
+	in.ConnectionPool.DeepCopyInto(&out.ConnectionPool)
 	return
 }
 
@@ -417,6 +471,16 @@ func (in *PostgresSpec) DeepCopyInto(out *PostgresSpec) {
 	out.Volume = in.Volume
 	in.Patroni.DeepCopyInto(&out.Patroni)
 	out.Resources = in.Resources
+	if in.EnableConnectionPool != nil {
+		in, out := &in.EnableConnectionPool, &out.EnableConnectionPool
+		*out = new(bool)
+		**out = **in
+	}
+	if in.ConnectionPool != nil {
+		in, out := &in.ConnectionPool, &out.ConnectionPool
+		*out = new(ConnectionPool)
+		(*in).DeepCopyInto(*out)
+	}
 	if in.SpiloFSGroup != nil {
 		in, out := &in.SpiloFSGroup, &out.SpiloFSGroup
 		*out = new(int64)

pkg/cluster/cluster.go

@@ -11,6 +11,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/r3labs/diff"
 	"github.com/sirupsen/logrus"
 	appsv1 "k8s.io/api/apps/v1"
 	v1 "k8s.io/api/core/v1"
@@ -48,11 +49,26 @@ type Config struct {
 	PodServiceAccountRoleBinding *rbacv1.RoleBinding
 }
 
+// K8S objects that are belongs to a connection pool
+type ConnectionPoolObjects struct {
+	Deployment *appsv1.Deployment
+	Service    *v1.Service
+
+	// It could happen that a connection pool was enabled, but the operator was
+	// not able to properly process a corresponding event or was restarted. In
+	// this case we will miss missing/require situation and a lookup function
+	// will not be installed. To avoid synchronizing it all the time to prevent
+	// this, we can remember the result in memory at least until the next
+	// restart.
+	LookupFunction bool
+}
+
 type kubeResources struct {
 	Services            map[PostgresRole]*v1.Service
 	Endpoints           map[PostgresRole]*v1.Endpoints
 	Secrets             map[types.UID]*v1.Secret
 	Statefulset         *appsv1.StatefulSet
+	ConnectionPool      *ConnectionPoolObjects
 	PodDisruptionBudget *policybeta1.PodDisruptionBudget
 	//Pods are treated separately
 	//PVCs are treated separately
@@ -184,7 +200,8 @@ func (c *Cluster) isNewCluster() bool {
 func (c *Cluster) initUsers() error {
 	c.setProcessName("initializing users")
 
-	// clear our the previous state of the cluster users (in case we are running a sync).
+	// clear our the previous state of the cluster users (in case we are
+	// running a sync).
 	c.systemUsers = map[string]spec.PgUser{}
 	c.pgUsers = map[string]spec.PgUser{}
 
@@ -292,8 +309,10 @@ func (c *Cluster) Create() error {
 	}
 	c.logger.Infof("pods are ready")
 
-	// create database objects unless we are running without pods or disabled that feature explicitly
+	// create database objects unless we are running without pods or disabled
+	// that feature explicitly
 	if !(c.databaseAccessDisabled() || c.getNumberOfInstances(&c.Spec) <= 0 || c.Spec.StandbyCluster != nil) {
+		c.logger.Infof("Create roles")
 		if err = c.createRoles(); err != nil {
 			return fmt.Errorf("could not create users: %v", err)
 		}
@@ -316,6 +335,26 @@ func (c *Cluster) Create() error {
 		c.logger.Errorf("could not list resources: %v", err)
 	}
 
+	// Create connection pool deployment and services if necessary. Since we
+	// need to peform some operations with the database itself (e.g. install
+	// lookup function), do it as the last step, when everything is available.
+	//
+	// Do not consider connection pool as a strict requirement, and if
+	// something fails, report warning
+	if c.needConnectionPool() {
+		if c.ConnectionPool != nil {
+			c.logger.Warning("Connection pool already exists in the cluster")
+			return nil
+		}
+		connPool, err := c.createConnectionPool(c.installLookupFunction)
+		if err != nil {
+			c.logger.Warningf("could not create connection pool: %v", err)
+			return nil
+		}
+		c.logger.Infof("connection pool %q has been successfully created",
+			util.NameFromMeta(connPool.Deployment.ObjectMeta))
+	}
+
 	return nil
 }
 
@@ -571,7 +610,11 @@ func (c *Cluster) Update(oldSpec, newSpec *acidv1.Postgresql) error {
 		}
 	}
 
-	if !reflect.DeepEqual(oldSpec.Spec.Users, newSpec.Spec.Users) {
+	// connection pool needs one system user created, which is done in
+	// initUsers. Check if it needs to be called.
+	sameUsers := reflect.DeepEqual(oldSpec.Spec.Users, newSpec.Spec.Users)
+	needConnPool := c.needConnectionPoolWorker(&newSpec.Spec)
+	if !sameUsers || needConnPool {
 		c.logger.Debugf("syncing secrets")
 		if err := c.initUsers(); err != nil {
 			c.logger.Errorf("could not init users: %v", err)
@@ -695,6 +738,11 @@ func (c *Cluster) Update(oldSpec, newSpec *acidv1.Postgresql) error {
 		}
 	}
 
+	// sync connection pool
+	if err := c.syncConnectionPool(oldSpec, newSpec, c.installLookupFunction); err != nil {
+		return fmt.Errorf("could not sync connection pool: %v", err)
+	}
+
 	return nil
 }
 
@@ -746,6 +794,12 @@ func (c *Cluster) Delete() {
 		c.logger.Warningf("could not remove leftover patroni objects; %v", err)
 	}
 
+	// Delete connection pool objects anyway, even if it's not mentioned in the
+	// manifest, just to not keep orphaned components in case if something went
+	// wrong
+	if err := c.deleteConnectionPool(); err != nil {
+		c.logger.Warningf("could not remove connection pool: %v", err)
+	}
 }
 
 //NeedsRepair returns true if the cluster should be included in the repair scan (based on its in-memory status).
@@ -812,6 +866,35 @@ func (c *Cluster) initSystemUsers() {
 		Name:     c.OpConfig.ReplicationUsername,
 		Password: util.RandomPassword(constants.PasswordLength),
 	}
+
+	// Connection pool user is an exception, if requested it's going to be
+	// created by operator as a normal pgUser
+	if c.needConnectionPool() {
+		// initialize empty connection pool if not done yet
+		if c.Spec.ConnectionPool == nil {
+			c.Spec.ConnectionPool = &acidv1.ConnectionPool{}
+		}
+
+		username := util.Coalesce(
+			c.Spec.ConnectionPool.User,
+			c.OpConfig.ConnectionPool.User)
+
+		// connection pooler application should be able to login with this role
+		connPoolUser := spec.PgUser{
+			Origin:   spec.RoleConnectionPool,
+			Name:     username,
+			Flags:    []string{constants.RoleFlagLogin},
+			Password: util.RandomPassword(constants.PasswordLength),
+		}
+
+		if _, exists := c.pgUsers[username]; !exists {
+			c.pgUsers[username] = connPoolUser
+		}
+
+		if _, exists := c.systemUsers[constants.ConnectionPoolUserKeyName]; !exists {
+			c.systemUsers[constants.ConnectionPoolUserKeyName] = connPoolUser
+		}
+	}
 }
 
 func (c *Cluster) initRobotUsers() error {
@@ -1138,3 +1221,119 @@ func (c *Cluster) deletePatroniClusterConfigMaps() error {
 
 	return c.deleteClusterObject(get, deleteConfigMapFn, "configmap")
 }
+
+// Test if two connection pool configuration needs to be synced. For simplicity
+// compare not the actual K8S objects, but the configuration itself and request
+// sync if there is any difference.
+func (c *Cluster) needSyncConnPoolSpecs(oldSpec, newSpec *acidv1.ConnectionPool) (sync bool, reasons []string) {
+	reasons = []string{}
+	sync = false
+
+	changelog, err := diff.Diff(oldSpec, newSpec)
+	if err != nil {
+		c.logger.Infof("Cannot get diff, do not do anything, %+v", err)
+		return false, reasons
+	}
+
+	if len(changelog) > 0 {
+		sync = true
+	}
+
+	for _, change := range changelog {
+		msg := fmt.Sprintf("%s %+v from '%+v' to '%+v'",
+			change.Type, change.Path, change.From, change.To)
+		reasons = append(reasons, msg)
+	}
+
+	return sync, reasons
+}
+
+func syncResources(a, b *v1.ResourceRequirements) bool {
+	for _, res := range []v1.ResourceName{
+		v1.ResourceCPU,
+		v1.ResourceMemory,
+	} {
+		if !a.Limits[res].Equal(b.Limits[res]) ||
+			!a.Requests[res].Equal(b.Requests[res]) {
+			return true
+		}
+	}
+
+	return false
+}
+
+// Check if we need to synchronize connection pool deployment due to new
+// defaults, that are different from what we see in the DeploymentSpec
+func (c *Cluster) needSyncConnPoolDefaults(
+	spec *acidv1.ConnectionPool,
+	deployment *appsv1.Deployment) (sync bool, reasons []string) {
+
+	reasons = []string{}
+	sync = false
+
+	config := c.OpConfig.ConnectionPool
+	podTemplate := deployment.Spec.Template
+	poolContainer := podTemplate.Spec.Containers[constants.ConnPoolContainer]
+
+	if spec == nil {
+		spec = &acidv1.ConnectionPool{}
+	}
+
+	if spec.NumberOfInstances == nil &&
+		*deployment.Spec.Replicas != *config.NumberOfInstances {
+
+		sync = true
+		msg := fmt.Sprintf("NumberOfInstances is different (having %d, required %d)",
+			*deployment.Spec.Replicas, *config.NumberOfInstances)
+		reasons = append(reasons, msg)
+	}
+
+	if spec.DockerImage == "" &&
+		poolContainer.Image != config.Image {
+
+		sync = true
+		msg := fmt.Sprintf("DockerImage is different (having %s, required %s)",
+			poolContainer.Image, config.Image)
+		reasons = append(reasons, msg)
+	}
+
+	expectedResources, err := generateResourceRequirements(spec.Resources,
+		c.makeDefaultConnPoolResources())
+
+	// An error to generate expected resources means something is not quite
+	// right, but for the purpose of robustness do not panic here, just report
+	// and ignore resources comparison (in the worst case there will be no
+	// updates for new resource values).
+	if err == nil && syncResources(&poolContainer.Resources, expectedResources) {
+		sync = true
+		msg := fmt.Sprintf("Resources are different (having %+v, required %+v)",
+			poolContainer.Resources, expectedResources)
+		reasons = append(reasons, msg)
+	}
+
+	if err != nil {
+		c.logger.Warningf("Cannot generate expected resources, %v", err)
+	}
+
+	for _, env := range poolContainer.Env {
+		if spec.User == "" && env.Name == "PGUSER" {
+			ref := env.ValueFrom.SecretKeyRef.LocalObjectReference
+
+			if ref.Name != c.credentialSecretName(config.User) {
+				sync = true
+				msg := fmt.Sprintf("Pool user is different (having %s, required %s)",
+					ref.Name, config.User)
+				reasons = append(reasons, msg)
+			}
+		}
+
+		if spec.Schema == "" && env.Name == "PGSCHEMA" && env.Value != config.Schema {
+			sync = true
+			msg := fmt.Sprintf("Pool schema is different (having %s, required %s)",
+				env.Value, config.Schema)
+			reasons = append(reasons, msg)
+		}
+	}
+
+	return sync, reasons
+}

pkg/cluster/cluster_test.go

@@ -9,6 +9,7 @@ import (
 	acidv1 "github.com/zalando/postgres-operator/pkg/apis/acid.zalan.do/v1"
 	"github.com/zalando/postgres-operator/pkg/spec"
 	"github.com/zalando/postgres-operator/pkg/util/config"
+	"github.com/zalando/postgres-operator/pkg/util/constants"
 	"github.com/zalando/postgres-operator/pkg/util/k8sutil"
 	"github.com/zalando/postgres-operator/pkg/util/teams"
 	v1 "k8s.io/api/core/v1"
@@ -704,3 +705,20 @@ func TestServiceAnnotations(t *testing.T) {
 		})
 	}
 }
+
+func TestInitSystemUsers(t *testing.T) {
+	testName := "Test system users initialization"
+
+	// default cluster without connection pool
+	cl.initSystemUsers()
+	if _, exist := cl.systemUsers[constants.ConnectionPoolUserKeyName]; exist {
+		t.Errorf("%s, connection pool user is present", testName)
+	}
+
+	// cluster with connection pool
+	cl.Spec.EnableConnectionPool = boolToPointer(true)
+	cl.initSystemUsers()
+	if _, exist := cl.systemUsers[constants.ConnectionPoolUserKeyName]; !exist {
+		t.Errorf("%s, connection pool user is not present", testName)
+	}
+}

pkg/cluster/database.go

@@ -1,10 +1,12 @@
 package cluster
 
 import (
+	"bytes"
 	"database/sql"
 	"fmt"
 	"net"
 	"strings"
+	"text/template"
 	"time"
 
 	"github.com/lib/pq"
@@ -28,13 +30,37 @@ const (
 	getDatabasesSQL       = `SELECT datname, pg_get_userbyid(datdba) AS owner FROM pg_database;`
 	createDatabaseSQL     = `CREATE DATABASE "%s" OWNER "%s";`
 	alterDatabaseOwnerSQL = `ALTER DATABASE "%s" OWNER TO "%s";`
+	connectionPoolLookup  = `
+		CREATE SCHEMA IF NOT EXISTS {{.pool_schema}};
+
+		CREATE OR REPLACE FUNCTION {{.pool_schema}}.user_lookup(
+			in i_username text, out uname text, out phash text)
+		RETURNS record AS $$
+		BEGIN
+			SELECT usename, passwd FROM pg_catalog.pg_shadow
+			WHERE usename = i_username INTO uname, phash;
+			RETURN;
+		END;
+		$$ LANGUAGE plpgsql SECURITY DEFINER;
+
+		REVOKE ALL ON FUNCTION {{.pool_schema}}.user_lookup(text)
+			FROM public, {{.pool_user}};
+		GRANT EXECUTE ON FUNCTION {{.pool_schema}}.user_lookup(text)
+			TO {{.pool_user}};
+		GRANT USAGE ON SCHEMA {{.pool_schema}} TO {{.pool_user}};
+	`
 )
 
-func (c *Cluster) pgConnectionString() string {
+func (c *Cluster) pgConnectionString(dbname string) string {
 	password := c.systemUsers[constants.SuperuserKeyName].Password
 
-	return fmt.Sprintf("host='%s' dbname=postgres sslmode=require user='%s' password='%s' connect_timeout='%d'",
+	if dbname == "" {
+		dbname = "postgres"
+	}
+
+	return fmt.Sprintf("host='%s' dbname='%s' sslmode=require user='%s' password='%s' connect_timeout='%d'",
 		fmt.Sprintf("%s.%s.svc.%s", c.Name, c.Namespace, c.OpConfig.ClusterDomain),
+		dbname,
 		c.systemUsers[constants.SuperuserKeyName].Name,
 		strings.Replace(password, "$", "\\$", -1),
 		constants.PostgresConnectTimeout/time.Second)
@@ -49,13 +75,17 @@ func (c *Cluster) databaseAccessDisabled() bool {
 }
 
 func (c *Cluster) initDbConn() error {
+	return c.initDbConnWithName("")
+}
+
+func (c *Cluster) initDbConnWithName(dbname string) error {
 	c.setProcessName("initializing db connection")
 	if c.pgDb != nil {
 		return nil
 	}
 
 	var conn *sql.DB
-	connstring := c.pgConnectionString()
+	connstring := c.pgConnectionString(dbname)
 
 	finalerr := retryutil.Retry(constants.PostgresConnectTimeout, constants.PostgresConnectRetryTimeout,
 		func() (bool, error) {
@@ -94,6 +124,10 @@ func (c *Cluster) initDbConn() error {
 	return nil
 }
 
+func (c *Cluster) connectionIsClosed() bool {
+	return c.pgDb == nil
+}
+
 func (c *Cluster) closeDbConn() (err error) {
 	c.setProcessName("closing db connection")
 	if c.pgDb != nil {
@@ -243,3 +277,88 @@ func makeUserFlags(rolsuper, rolinherit, rolcreaterole, rolcreatedb, rolcanlogin
 
 	return result
 }
+
+// Creates a connection pool credentials lookup function in every database to
+// perform remote authentification.
+func (c *Cluster) installLookupFunction(poolSchema, poolUser string) error {
+	var stmtBytes bytes.Buffer
+	c.logger.Info("Installing lookup function")
+
+	if err := c.initDbConn(); err != nil {
+		return fmt.Errorf("could not init database connection")
+	}
+	defer func() {
+		if c.connectionIsClosed() {
+			return
+		}
+
+		if err := c.closeDbConn(); err != nil {
+			c.logger.Errorf("could not close database connection: %v", err)
+		}
+	}()
+
+	currentDatabases, err := c.getDatabases()
+	if err != nil {
+		msg := "could not get databases to install pool lookup function: %v"
+		return fmt.Errorf(msg, err)
+	}
+
+	templater := template.Must(template.New("sql").Parse(connectionPoolLookup))
+
+	for dbname, _ := range currentDatabases {
+		if dbname == "template0" || dbname == "template1" {
+			continue
+		}
+
+		if err := c.initDbConnWithName(dbname); err != nil {
+			return fmt.Errorf("could not init database connection to %s", dbname)
+		}
+
+		c.logger.Infof("Install pool lookup function into %s", dbname)
+
+		params := TemplateParams{
+			"pool_schema": poolSchema,
+			"pool_user":   poolUser,
+		}
+
+		if err := templater.Execute(&stmtBytes, params); err != nil {
+			c.logger.Errorf("could not prepare sql statement %+v: %v",
+				params, err)
+			// process other databases
+			continue
+		}
+
+		// golang sql will do retries couple of times if pq driver reports
+		// connections issues (driver.ErrBadConn), but since our query is
+		// idempotent, we can retry in a view of other errors (e.g. due to
+		// failover a db is temporary in a read-only mode or so) to make sure
+		// it was applied.
+		execErr := retryutil.Retry(
+			constants.PostgresConnectTimeout,
+			constants.PostgresConnectRetryTimeout,
+			func() (bool, error) {
+				if _, err := c.pgDb.Exec(stmtBytes.String()); err != nil {
+					msg := fmt.Errorf("could not execute sql statement %s: %v",
+						stmtBytes.String(), err)
+					return false, msg
+				}
+
+				return true, nil
+			})
+
+		if execErr != nil {
+			c.logger.Errorf("could not execute after retries %s: %v",
+				stmtBytes.String(), err)
+			// process other databases
+			continue
+		}
+
+		c.logger.Infof("Pool lookup function installed into %s", dbname)
+		if err := c.closeDbConn(); err != nil {
+			c.logger.Errorf("could not close database connection: %v", err)
+		}
+	}
+
+	c.ConnectionPool.LookupFunction = true
+	return nil
+}

pkg/cluster/k8sres.go

@@ -18,6 +18,7 @@ import (
 
 	acidv1 "github.com/zalando/postgres-operator/pkg/apis/acid.zalan.do/v1"
 	"github.com/zalando/postgres-operator/pkg/spec"
+	pkgspec "github.com/zalando/postgres-operator/pkg/spec"
 	"github.com/zalando/postgres-operator/pkg/util"
 	"github.com/zalando/postgres-operator/pkg/util/config"
 	"github.com/zalando/postgres-operator/pkg/util/constants"
@@ -32,10 +33,12 @@ const (
 	patroniPGBinariesParameterName   = "bin_dir"
 	patroniPGParametersParameterName = "parameters"
 	patroniPGHBAConfParameterName    = "pg_hba"
+	localHost                        = "127.0.0.1/32"
+	connectionPoolContainer          = "connection-pool"
+	pgPort                           = 5432
 
 	// the gid of the postgres user in the default spilo image
 	spiloPostgresGID = 103
-	localHost        = "127.0.0.1/32"
 )
 
 type pgUser struct {
@@ -71,6 +74,10 @@ func (c *Cluster) statefulSetName() string {
 	return c.Name
 }
 
+func (c *Cluster) connPoolName() string {
+	return c.Name + "-pooler"
+}
+
 func (c *Cluster) endpointName(role PostgresRole) string {
 	name := c.Name
 	if role == Replica {
@@ -89,6 +96,28 @@ func (c *Cluster) serviceName(role PostgresRole) string {
 	return name
 }
 
+func (c *Cluster) serviceAddress(role PostgresRole) string {
+	service, exist := c.Services[role]
+
+	if exist {
+		return service.ObjectMeta.Name
+	}
+
+	c.logger.Warningf("No service for role %s", role)
+	return ""
+}
+
+func (c *Cluster) servicePort(role PostgresRole) string {
+	service, exist := c.Services[role]
+
+	if exist {
+		return fmt.Sprint(service.Spec.Ports[0].Port)
+	}
+
+	c.logger.Warningf("No service for role %s", role)
+	return ""
+}
+
 func (c *Cluster) podDisruptionBudgetName() string {
 	return c.OpConfig.PDBNameFormat.Format("cluster", c.Name)
 }
@@ -97,10 +126,39 @@ func (c *Cluster) makeDefaultResources() acidv1.Resources {
 
 	config := c.OpConfig
 
-	defaultRequests := acidv1.ResourceDescription{CPU: config.DefaultCPURequest, Memory: config.DefaultMemoryRequest}
-	defaultLimits := acidv1.ResourceDescription{CPU: config.DefaultCPULimit, Memory: config.DefaultMemoryLimit}
+	defaultRequests := acidv1.ResourceDescription{
+		CPU:    config.Resources.DefaultCPURequest,
+		Memory: config.Resources.DefaultMemoryRequest,
+	}
+	defaultLimits := acidv1.ResourceDescription{
+		CPU:    config.Resources.DefaultCPULimit,
+		Memory: config.Resources.DefaultMemoryLimit,
+	}
 
-	return acidv1.Resources{ResourceRequests: defaultRequests, ResourceLimits: defaultLimits}
+	return acidv1.Resources{
+		ResourceRequests: defaultRequests,
+		ResourceLimits:   defaultLimits,
+	}
+}
+
+// Generate default resource section for connection pool deployment, to be used
+// if nothing custom is specified in the manifest
+func (c *Cluster) makeDefaultConnPoolResources() acidv1.Resources {
+	config := c.OpConfig
+
+	defaultRequests := acidv1.ResourceDescription{
+		CPU:    config.ConnectionPool.ConnPoolDefaultCPURequest,
+		Memory: config.ConnectionPool.ConnPoolDefaultMemoryRequest,
+	}
+	defaultLimits := acidv1.ResourceDescription{
+		CPU:    config.ConnectionPool.ConnPoolDefaultCPULimit,
+		Memory: config.ConnectionPool.ConnPoolDefaultMemoryLimit,
+	}
+
+	return acidv1.Resources{
+		ResourceRequests: defaultRequests,
+		ResourceLimits:   defaultLimits,
+	}
 }
 
 func generateResourceRequirements(resources acidv1.Resources, defaultResources acidv1.Resources) (*v1.ResourceRequirements, error) {
@@ -124,12 +182,12 @@ func generateResourceRequirements(resources acidv1.Resources, defaultResources a
 	return &result, nil
 }
 
-func fillResourceList(pgSpec acidv1.ResourceDescription, defaults acidv1.ResourceDescription) (v1.ResourceList, error) {
+func fillResourceList(spec acidv1.ResourceDescription, defaults acidv1.ResourceDescription) (v1.ResourceList, error) {
 	var err error
 	requests := v1.ResourceList{}
 
-	if pgSpec.CPU != "" {
-		requests[v1.ResourceCPU], err = resource.ParseQuantity(pgSpec.CPU)
+	if spec.CPU != "" {
+		requests[v1.ResourceCPU], err = resource.ParseQuantity(spec.CPU)
 		if err != nil {
 			return nil, fmt.Errorf("could not parse CPU quantity: %v", err)
 		}
@@ -139,8 +197,8 @@ func fillResourceList(pgSpec acidv1.ResourceDescription, defaults acidv1.Resourc
 			return nil, fmt.Errorf("could not parse default CPU quantity: %v", err)
 		}
 	}
-	if pgSpec.Memory != "" {
-		requests[v1.ResourceMemory], err = resource.ParseQuantity(pgSpec.Memory)
+	if spec.Memory != "" {
+		requests[v1.ResourceMemory], err = resource.ParseQuantity(spec.Memory)
 		if err != nil {
 			return nil, fmt.Errorf("could not parse memory quantity: %v", err)
 		}
@@ -320,7 +378,11 @@ func tolerations(tolerationsSpec *[]v1.Toleration, podToleration map[string]stri
 		return *tolerationsSpec
 	}
 
-	if len(podToleration["key"]) > 0 || len(podToleration["operator"]) > 0 || len(podToleration["value"]) > 0 || len(podToleration["effect"]) > 0 {
+	if len(podToleration["key"]) > 0 ||
+		len(podToleration["operator"]) > 0 ||
+		len(podToleration["value"]) > 0 ||
+		len(podToleration["effect"]) > 0 {
+
 		return []v1.Toleration{
 			{
 				Key:      podToleration["key"],
@@ -424,9 +486,9 @@ func generateSidecarContainers(sidecars []acidv1.Sidecar,
 
 // Check whether or not we're requested to mount an shm volume,
 // taking into account that PostgreSQL manifest has precedence.
-func mountShmVolumeNeeded(opConfig config.Config, pgSpec *acidv1.PostgresSpec) *bool {
-	if pgSpec.ShmVolume != nil && *pgSpec.ShmVolume {
-		return pgSpec.ShmVolume
+func mountShmVolumeNeeded(opConfig config.Config, spec *acidv1.PostgresSpec) *bool {
+	if spec.ShmVolume != nil && *spec.ShmVolume {
+		return spec.ShmVolume
 	}
 
 	return opConfig.ShmVolume
@@ -550,10 +612,6 @@ func (c *Cluster) generateSpiloPodEnvVars(uid types.UID, spiloConfiguration stri
 			Name:  "KUBERNETES_ROLE_LABEL",
 			Value: c.OpConfig.PodRoleLabel,
 		},
-		{
-			Name:  "KUBERNETES_LABELS",
-			Value: labels.Set(c.OpConfig.ClusterLabels).String(),
-		},
 		{
 			Name: "PGPASSWORD_SUPERUSER",
 			ValueFrom: &v1.EnvVarSource{
@@ -589,6 +647,12 @@ func (c *Cluster) generateSpiloPodEnvVars(uid types.UID, spiloConfiguration stri
 			Value: c.OpConfig.PamRoleName,
 		},
 	}
+	// Spilo expects cluster labels as JSON
+	if clusterLabels, err := json.Marshal(labels.Set(c.OpConfig.ClusterLabels)); err != nil {
+		envVars = append(envVars, v1.EnvVar{Name: "KUBERNETES_LABELS", Value: labels.Set(c.OpConfig.ClusterLabels).String()})
+	} else {
+		envVars = append(envVars, v1.EnvVar{Name: "KUBERNETES_LABELS", Value: string(clusterLabels)})
+	}
 	if spiloConfiguration != "" {
 		envVars = append(envVars, v1.EnvVar{Name: "SPILO_CONFIGURATION", Value: spiloConfiguration})
 	}
@@ -767,7 +831,7 @@ func (c *Cluster) getNewPgVersion(container v1.Container, newPgVersion string) (
 	return newPgVersion, nil
 }
 
-func (c *Cluster) generateStatefulSet(pgSpec *acidv1.PostgresSpec) (*appsv1.StatefulSet, error) {
+func (c *Cluster) generateStatefulSet(spec *acidv1.PostgresSpec) (*appsv1.StatefulSet, error) {
 
 	var (
 		err                 error
@@ -783,14 +847,14 @@ func (c *Cluster) generateStatefulSet(pgSpec *acidv1.PostgresSpec) (*appsv1.Stat
 
 		// controller adjusts the default memory request at operator startup
 
-		request := pgSpec.Resources.ResourceRequests.Memory
+		request := spec.Resources.ResourceRequests.Memory
 		if request == "" {
-			request = c.OpConfig.DefaultMemoryRequest
+			request = c.OpConfig.Resources.DefaultMemoryRequest
 		}
 
-		limit := pgSpec.Resources.ResourceLimits.Memory
+		limit := spec.Resources.ResourceLimits.Memory
 		if limit == "" {
-			limit = c.OpConfig.DefaultMemoryLimit
+			limit = c.OpConfig.Resources.DefaultMemoryLimit
 		}
 
 		isSmaller, err := util.IsSmallerQuantity(request, limit)
@@ -799,7 +863,7 @@ func (c *Cluster) generateStatefulSet(pgSpec *acidv1.PostgresSpec) (*appsv1.Stat
 		}
 		if isSmaller {
 			c.logger.Warningf("The memory request of %v for the Postgres container is increased to match the memory limit of %v.", request, limit)
-			pgSpec.Resources.ResourceRequests.Memory = limit
+			spec.Resources.ResourceRequests.Memory = limit
 
 		}
 
@@ -807,17 +871,17 @@ func (c *Cluster) generateStatefulSet(pgSpec *acidv1.PostgresSpec) (*appsv1.Stat
 		// as this sidecar is managed separately
 
 		// adjust sidecar containers defined for that particular cluster
-		for _, sidecar := range pgSpec.Sidecars {
+		for _, sidecar := range spec.Sidecars {
 
 			// TODO #413
 			sidecarRequest := sidecar.Resources.ResourceRequests.Memory
 			if request == "" {
-				request = c.OpConfig.DefaultMemoryRequest
+				request = c.OpConfig.Resources.DefaultMemoryRequest
 			}
 
 			sidecarLimit := sidecar.Resources.ResourceLimits.Memory
 			if limit == "" {
-				limit = c.OpConfig.DefaultMemoryLimit
+				limit = c.OpConfig.Resources.DefaultMemoryLimit
 			}
 
 			isSmaller, err := util.IsSmallerQuantity(sidecarRequest, sidecarLimit)
@@ -834,21 +898,21 @@ func (c *Cluster) generateStatefulSet(pgSpec *acidv1.PostgresSpec) (*appsv1.Stat
 
 	defaultResources := c.makeDefaultResources()
 
-	resourceRequirements, err := generateResourceRequirements(pgSpec.Resources, defaultResources)
+	resourceRequirements, err := generateResourceRequirements(spec.Resources, defaultResources)
 	if err != nil {
 		return nil, fmt.Errorf("could not generate resource requirements: %v", err)
 	}
 
-	if pgSpec.InitContainers != nil && len(pgSpec.InitContainers) > 0 {
+	if spec.InitContainers != nil && len(spec.InitContainers) > 0 {
 		if c.OpConfig.EnableInitContainers != nil && !(*c.OpConfig.EnableInitContainers) {
 			c.logger.Warningf("initContainers specified but disabled in configuration - next statefulset creation would fail")
 		}
-		initContainers = pgSpec.InitContainers
+		initContainers = spec.InitContainers
 	}
 
 	customPodEnvVarsList := make([]v1.EnvVar, 0)
 
-	if c.OpConfig.PodEnvironmentConfigMap != (spec.NamespacedName{}) {
+	if c.OpConfig.PodEnvironmentConfigMap != (pkgspec.NamespacedName{}) {
 		var cm *v1.ConfigMap
 		cm, err = c.KubeClient.ConfigMaps(c.OpConfig.PodEnvironmentConfigMap.Namespace).Get(c.OpConfig.PodEnvironmentConfigMap.Name, metav1.GetOptions{})
 		if err != nil {
@@ -866,33 +930,33 @@ func (c *Cluster) generateStatefulSet(pgSpec *acidv1.PostgresSpec) (*appsv1.Stat
 		sort.Slice(customPodEnvVarsList,
 			func(i, j int) bool { return customPodEnvVarsList[i].Name < customPodEnvVarsList[j].Name })
 	}
-	if pgSpec.StandbyCluster != nil && pgSpec.StandbyCluster.S3WalPath == "" {
+	if spec.StandbyCluster != nil && spec.StandbyCluster.S3WalPath == "" {
 		return nil, fmt.Errorf("s3_wal_path is empty for standby cluster")
 	}
 
 	// backward compatible check for InitContainers
-	if pgSpec.InitContainersOld != nil {
+	if spec.InitContainersOld != nil {
 		msg := "Manifest parameter init_containers is deprecated."
-		if pgSpec.InitContainers == nil {
+		if spec.InitContainers == nil {
 			c.logger.Warningf("%s Consider using initContainers instead.", msg)
-			pgSpec.InitContainers = pgSpec.InitContainersOld
+			spec.InitContainers = spec.InitContainersOld
 		} else {
 			c.logger.Warningf("%s Only value from initContainers is used", msg)
 		}
 	}
 
 	// backward compatible check for PodPriorityClassName
-	if pgSpec.PodPriorityClassNameOld != "" {
+	if spec.PodPriorityClassNameOld != "" {
 		msg := "Manifest parameter pod_priority_class_name is deprecated."
-		if pgSpec.PodPriorityClassName == "" {
+		if spec.PodPriorityClassName == "" {
 			c.logger.Warningf("%s Consider using podPriorityClassName instead.", msg)
-			pgSpec.PodPriorityClassName = pgSpec.PodPriorityClassNameOld
+			spec.PodPriorityClassName = spec.PodPriorityClassNameOld
 		} else {
 			c.logger.Warningf("%s Only value from podPriorityClassName is used", msg)
 		}
 	}
 
-	spiloConfiguration, err := generateSpiloJSONConfiguration(&pgSpec.PostgresqlParam, &pgSpec.Patroni, c.OpConfig.PamRoleName, c.logger)
+	spiloConfiguration, err := generateSpiloJSONConfiguration(&spec.PostgresqlParam, &spec.Patroni, c.OpConfig.PamRoleName, c.logger)
 	if err != nil {
 		return nil, fmt.Errorf("could not generate Spilo JSON configuration: %v", err)
 	}
@@ -901,24 +965,24 @@ func (c *Cluster) generateStatefulSet(pgSpec *acidv1.PostgresSpec) (*appsv1.Stat
 	spiloEnvVars := c.generateSpiloPodEnvVars(
 		c.Postgresql.GetUID(),
 		spiloConfiguration,
-		&pgSpec.Clone,
-		pgSpec.StandbyCluster,
+		&spec.Clone,
+		spec.StandbyCluster,
 		customPodEnvVarsList,
 	)
 
 	// pickup the docker image for the spilo container
-	effectiveDockerImage := util.Coalesce(pgSpec.DockerImage, c.OpConfig.DockerImage)
+	effectiveDockerImage := util.Coalesce(spec.DockerImage, c.OpConfig.DockerImage)
 
 	// determine the FSGroup for the spilo pod
 	effectiveFSGroup := c.OpConfig.Resources.SpiloFSGroup
-	if pgSpec.SpiloFSGroup != nil {
-		effectiveFSGroup = pgSpec.SpiloFSGroup
+	if spec.SpiloFSGroup != nil {
+		effectiveFSGroup = spec.SpiloFSGroup
 	}
 
-	volumeMounts := generateVolumeMounts(pgSpec.Volume)
+	volumeMounts := generateVolumeMounts(spec.Volume)
 
 	// configure TLS with a custom secret volume
-	if pgSpec.TLS != nil && pgSpec.TLS.SecretName != "" {
+	if spec.TLS != nil && spec.TLS.SecretName != "" {
 		if effectiveFSGroup == nil {
 			c.logger.Warnf("Setting the default FSGroup to satisfy the TLS configuration")
 			fsGroup := int64(spiloPostgresGID)
@@ -931,7 +995,7 @@ func (c *Cluster) generateStatefulSet(pgSpec *acidv1.PostgresSpec) (*appsv1.Stat
 			Name: "tls-secret",
 			VolumeSource: v1.VolumeSource{
 				Secret: &v1.SecretVolumeSource{
-					SecretName:  pgSpec.TLS.SecretName,
+					SecretName:  spec.TLS.SecretName,
 					DefaultMode: &defaultMode,
 				},
 			},
@@ -945,16 +1009,16 @@ func (c *Cluster) generateStatefulSet(pgSpec *acidv1.PostgresSpec) (*appsv1.Stat
 		})
 
 		// use the same filenames as Secret resources by default
-		certFile := ensurePath(pgSpec.TLS.CertificateFile, mountPath, "tls.crt")
-		privateKeyFile := ensurePath(pgSpec.TLS.PrivateKeyFile, mountPath, "tls.key")
+		certFile := ensurePath(spec.TLS.CertificateFile, mountPath, "tls.crt")
+		privateKeyFile := ensurePath(spec.TLS.PrivateKeyFile, mountPath, "tls.key")
 		spiloEnvVars = append(
 			spiloEnvVars,
 			v1.EnvVar{Name: "SSL_CERTIFICATE_FILE", Value: certFile},
 			v1.EnvVar{Name: "SSL_PRIVATE_KEY_FILE", Value: privateKeyFile},
 		)
 
-		if pgSpec.TLS.CAFile != "" {
-			caFile := ensurePath(pgSpec.TLS.CAFile, mountPath, "")
+		if spec.TLS.CAFile != "" {
+			caFile := ensurePath(spec.TLS.CAFile, mountPath, "")
 			spiloEnvVars = append(
 				spiloEnvVars,
 				v1.EnvVar{Name: "SSL_CA_FILE", Value: caFile},
@@ -973,7 +1037,7 @@ func (c *Cluster) generateStatefulSet(pgSpec *acidv1.PostgresSpec) (*appsv1.Stat
 	)
 
 	// resolve conflicts between operator-global and per-cluster sidecars
-	sideCars := c.mergeSidecars(pgSpec.Sidecars)
+	sideCars := c.mergeSidecars(spec.Sidecars)
 
 	resourceRequirementsScalyrSidecar := makeResources(
 		c.OpConfig.ScalyrCPURequest,
@@ -1003,10 +1067,10 @@ func (c *Cluster) generateStatefulSet(pgSpec *acidv1.PostgresSpec) (*appsv1.Stat
 		}
 	}
 
-	tolerationSpec := tolerations(&pgSpec.Tolerations, c.OpConfig.PodToleration)
-	effectivePodPriorityClassName := util.Coalesce(pgSpec.PodPriorityClassName, c.OpConfig.PodPriorityClassName)
+	tolerationSpec := tolerations(&spec.Tolerations, c.OpConfig.PodToleration)
+	effectivePodPriorityClassName := util.Coalesce(spec.PodPriorityClassName, c.OpConfig.PodPriorityClassName)
 
-	annotations := c.generatePodAnnotations(pgSpec)
+	annotations := c.generatePodAnnotations(spec)
 
 	// generate pod template for the statefulset, based on the spilo container and sidecars
 	podTemplate, err = generatePodTemplate(
@@ -1023,7 +1087,7 @@ func (c *Cluster) generateStatefulSet(pgSpec *acidv1.PostgresSpec) (*appsv1.Stat
 		c.OpConfig.PodServiceAccountName,
 		c.OpConfig.KubeIAMRole,
 		effectivePodPriorityClassName,
-		mountShmVolumeNeeded(c.OpConfig, pgSpec),
+		mountShmVolumeNeeded(c.OpConfig, spec),
 		c.OpConfig.EnablePodAntiAffinity,
 		c.OpConfig.PodAntiAffinityTopologyKey,
 		c.OpConfig.AdditionalSecretMount,
@@ -1034,12 +1098,12 @@ func (c *Cluster) generateStatefulSet(pgSpec *acidv1.PostgresSpec) (*appsv1.Stat
 		return nil, fmt.Errorf("could not generate pod template: %v", err)
 	}
 
-	if volumeClaimTemplate, err = generatePersistentVolumeClaimTemplate(pgSpec.Volume.Size,
-		pgSpec.Volume.StorageClass); err != nil {
+	if volumeClaimTemplate, err = generatePersistentVolumeClaimTemplate(spec.Volume.Size,
+		spec.Volume.StorageClass); err != nil {
 		return nil, fmt.Errorf("could not generate volume claim template: %v", err)
 	}
 
-	numberOfInstances := c.getNumberOfInstances(pgSpec)
+	numberOfInstances := c.getNumberOfInstances(spec)
 
 	// the operator has domain-specific logic on how to do rolling updates of PG clusters
 	// so we do not use default rolling updates implemented by stateful sets
@@ -1076,13 +1140,13 @@ func (c *Cluster) generateStatefulSet(pgSpec *acidv1.PostgresSpec) (*appsv1.Stat
 	return statefulSet, nil
 }
 
-func (c *Cluster) generatePodAnnotations(pgSpec *acidv1.PostgresSpec) map[string]string {
+func (c *Cluster) generatePodAnnotations(spec *acidv1.PostgresSpec) map[string]string {
 	annotations := make(map[string]string)
 	for k, v := range c.OpConfig.CustomPodAnnotations {
 		annotations[k] = v
 	}
-	if pgSpec != nil || pgSpec.PodAnnotations != nil {
-		for k, v := range pgSpec.PodAnnotations {
+	if spec != nil || spec.PodAnnotations != nil {
+		for k, v := range spec.PodAnnotations {
 			annotations[k] = v
 		}
 	}
@@ -1148,13 +1212,13 @@ func (c *Cluster) mergeSidecars(sidecars []acidv1.Sidecar) []acidv1.Sidecar {
 	return result
 }
 
-func (c *Cluster) getNumberOfInstances(pgSpec *acidv1.PostgresSpec) int32 {
+func (c *Cluster) getNumberOfInstances(spec *acidv1.PostgresSpec) int32 {
 	min := c.OpConfig.MinInstances
 	max := c.OpConfig.MaxInstances
-	cur := pgSpec.NumberOfInstances
+	cur := spec.NumberOfInstances
 	newcur := cur
 
-	if pgSpec.StandbyCluster != nil {
+	if spec.StandbyCluster != nil {
 		if newcur == 1 {
 			min = newcur
 			max = newcur
@@ -1309,15 +1373,15 @@ func (c *Cluster) generateSingleUserSecret(namespace string, pgUser spec.PgUser)
 	return &secret
 }
 
-func (c *Cluster) shouldCreateLoadBalancerForService(role PostgresRole, pgSpec *acidv1.PostgresSpec) bool {
+func (c *Cluster) shouldCreateLoadBalancerForService(role PostgresRole, spec *acidv1.PostgresSpec) bool {
 
 	switch role {
 
 	case Replica:
 
 		// if the value is explicitly set in a Postgresql manifest, follow this setting
-		if pgSpec.EnableReplicaLoadBalancer != nil {
-			return *pgSpec.EnableReplicaLoadBalancer
+		if spec.EnableReplicaLoadBalancer != nil {
+			return *spec.EnableReplicaLoadBalancer
 		}
 
 		// otherwise, follow the operator configuration
@@ -1325,8 +1389,8 @@ func (c *Cluster) shouldCreateLoadBalancerForService(role PostgresRole, pgSpec *
 
 	case Master:
 
-		if pgSpec.EnableMasterLoadBalancer != nil {
-			return *pgSpec.EnableMasterLoadBalancer
+		if spec.EnableMasterLoadBalancer != nil {
+			return *spec.EnableMasterLoadBalancer
 		}
 
 		return c.OpConfig.EnableMasterLoadBalancer
@@ -1337,7 +1401,7 @@ func (c *Cluster) shouldCreateLoadBalancerForService(role PostgresRole, pgSpec *
 
 }
 
-func (c *Cluster) generateService(role PostgresRole, pgSpec *acidv1.PostgresSpec) *v1.Service {
+func (c *Cluster) generateService(role PostgresRole, spec *acidv1.PostgresSpec) *v1.Service {
 	serviceSpec := v1.ServiceSpec{
 		Ports: []v1.ServicePort{{Name: "postgresql", Port: 5432, TargetPort: intstr.IntOrString{IntVal: 5432}}},
 		Type:  v1.ServiceTypeClusterIP,
@@ -1347,12 +1411,12 @@ func (c *Cluster) generateService(role PostgresRole, pgSpec *acidv1.PostgresSpec
 		serviceSpec.Selector = c.roleLabelsSet(false, role)
 	}
 
-	if c.shouldCreateLoadBalancerForService(role, pgSpec) {
+	if c.shouldCreateLoadBalancerForService(role, spec) {
 
-		// pgSpec.AllowedSourceRanges evaluates to the empty slice of zero length
+		// spec.AllowedSourceRanges evaluates to the empty slice of zero length
 		// when omitted or set to 'null'/empty sequence in the PG manifest
-		if len(pgSpec.AllowedSourceRanges) > 0 {
-			serviceSpec.LoadBalancerSourceRanges = pgSpec.AllowedSourceRanges
+		if len(spec.AllowedSourceRanges) > 0 {
+			serviceSpec.LoadBalancerSourceRanges = spec.AllowedSourceRanges
 		} else {
 			// safe default value: lock a load balancer only to the local address unless overridden explicitly
 			serviceSpec.LoadBalancerSourceRanges = []string{localHost}
@@ -1371,7 +1435,7 @@ func (c *Cluster) generateService(role PostgresRole, pgSpec *acidv1.PostgresSpec
 			Name:        c.serviceName(role),
 			Namespace:   c.Namespace,
 			Labels:      c.roleLabelsSet(true, role),
-			Annotations: c.generateServiceAnnotations(role, pgSpec),
+			Annotations: c.generateServiceAnnotations(role, spec),
 		},
 		Spec: serviceSpec,
 	}
@@ -1379,19 +1443,19 @@ func (c *Cluster) generateService(role PostgresRole, pgSpec *acidv1.PostgresSpec
 	return service
 }
 
-func (c *Cluster) generateServiceAnnotations(role PostgresRole, pgSpec *acidv1.PostgresSpec) map[string]string {
+func (c *Cluster) generateServiceAnnotations(role PostgresRole, spec *acidv1.PostgresSpec) map[string]string {
 	annotations := make(map[string]string)
 
 	for k, v := range c.OpConfig.CustomServiceAnnotations {
 		annotations[k] = v
 	}
-	if pgSpec != nil || pgSpec.ServiceAnnotations != nil {
-		for k, v := range pgSpec.ServiceAnnotations {
+	if spec != nil || spec.ServiceAnnotations != nil {
+		for k, v := range spec.ServiceAnnotations {
 			annotations[k] = v
 		}
 	}
 
-	if c.shouldCreateLoadBalancerForService(role, pgSpec) {
+	if c.shouldCreateLoadBalancerForService(role, spec) {
 		var dnsName string
 		if role == Master {
 			dnsName = c.masterDNSName()
@@ -1779,6 +1843,306 @@ func (c *Cluster) getLogicalBackupJobName() (jobName string) {
 	return "logical-backup-" + c.clusterName().Name
 }
 
+// Generate pool size related environment variables.
+//
+// MAX_DB_CONN would specify the global maximum for connections to a target
+// 	database.
+//
+// MAX_CLIENT_CONN is not configurable at the moment, just set it high enough.
+//
+// DEFAULT_SIZE is a pool size per db/user (having in mind the use case when
+// 	most of the queries coming through a connection pooler are from the same
+// 	user to the same db). In case if we want to spin up more connection pool
+// 	instances, take this into account and maintain the same number of
+// 	connections.
+//
+// MIN_SIZE is a pool minimal size, to prevent situation when sudden workload
+// 	have to wait for spinning up a new connections.
+//
+// RESERVE_SIZE is how many additional connections to allow for a pool.
+func (c *Cluster) getConnPoolEnvVars(spec *acidv1.PostgresSpec) []v1.EnvVar {
+	effectiveMode := util.Coalesce(
+		spec.ConnectionPool.Mode,
+		c.OpConfig.ConnectionPool.Mode)
+
+	numberOfInstances := spec.ConnectionPool.NumberOfInstances
+	if numberOfInstances == nil {
+		numberOfInstances = util.CoalesceInt32(
+			c.OpConfig.ConnectionPool.NumberOfInstances,
+			k8sutil.Int32ToPointer(1))
+	}
+
+	effectiveMaxDBConn := util.CoalesceInt32(
+		spec.ConnectionPool.MaxDBConnections,
+		c.OpConfig.ConnectionPool.MaxDBConnections)
+
+	if effectiveMaxDBConn == nil {
+		effectiveMaxDBConn = k8sutil.Int32ToPointer(
+			constants.ConnPoolMaxDBConnections)
+	}
+
+	maxDBConn := *effectiveMaxDBConn / *numberOfInstances
+
+	defaultSize := maxDBConn / 2
+	minSize := defaultSize / 2
+	reserveSize := minSize
+
+	return []v1.EnvVar{
+		{
+			Name:  "CONNECTION_POOL_PORT",
+			Value: fmt.Sprint(pgPort),
+		},
+		{
+			Name:  "CONNECTION_POOL_MODE",
+			Value: effectiveMode,
+		},
+		{
+			Name:  "CONNECTION_POOL_DEFAULT_SIZE",
+			Value: fmt.Sprint(defaultSize),
+		},
+		{
+			Name:  "CONNECTION_POOL_MIN_SIZE",
+			Value: fmt.Sprint(minSize),
+		},
+		{
+			Name:  "CONNECTION_POOL_RESERVE_SIZE",
+			Value: fmt.Sprint(reserveSize),
+		},
+		{
+			Name:  "CONNECTION_POOL_MAX_CLIENT_CONN",
+			Value: fmt.Sprint(constants.ConnPoolMaxClientConnections),
+		},
+		{
+			Name:  "CONNECTION_POOL_MAX_DB_CONN",
+			Value: fmt.Sprint(maxDBConn),
+		},
+	}
+}
+
+func (c *Cluster) generateConnPoolPodTemplate(spec *acidv1.PostgresSpec) (
+	*v1.PodTemplateSpec, error) {
+
+	gracePeriod := int64(c.OpConfig.PodTerminateGracePeriod.Seconds())
+	resources, err := generateResourceRequirements(
+		spec.ConnectionPool.Resources,
+		c.makeDefaultConnPoolResources())
+
+	effectiveDockerImage := util.Coalesce(
+		spec.ConnectionPool.DockerImage,
+		c.OpConfig.ConnectionPool.Image)
+
+	effectiveSchema := util.Coalesce(
+		spec.ConnectionPool.Schema,
+		c.OpConfig.ConnectionPool.Schema)
+
+	if err != nil {
+		return nil, fmt.Errorf("could not generate resource requirements: %v", err)
+	}
+
+	secretSelector := func(key string) *v1.SecretKeySelector {
+		effectiveUser := util.Coalesce(
+			spec.ConnectionPool.User,
+			c.OpConfig.ConnectionPool.User)
+
+		return &v1.SecretKeySelector{
+			LocalObjectReference: v1.LocalObjectReference{
+				Name: c.credentialSecretName(effectiveUser),
+			},
+			Key: key,
+		}
+	}
+
+	envVars := []v1.EnvVar{
+		{
+			Name:  "PGHOST",
+			Value: c.serviceAddress(Master),
+		},
+		{
+			Name:  "PGPORT",
+			Value: c.servicePort(Master),
+		},
+		{
+			Name: "PGUSER",
+			ValueFrom: &v1.EnvVarSource{
+				SecretKeyRef: secretSelector("username"),
+			},
+		},
+		// the convention is to use the same schema name as
+		// connection pool username
+		{
+			Name:  "PGSCHEMA",
+			Value: effectiveSchema,
+		},
+		{
+			Name: "PGPASSWORD",
+			ValueFrom: &v1.EnvVarSource{
+				SecretKeyRef: secretSelector("password"),
+			},
+		},
+	}
+
+	envVars = append(envVars, c.getConnPoolEnvVars(spec)...)
+
+	poolerContainer := v1.Container{
+		Name:            connectionPoolContainer,
+		Image:           effectiveDockerImage,
+		ImagePullPolicy: v1.PullIfNotPresent,
+		Resources:       *resources,
+		Ports: []v1.ContainerPort{
+			{
+				ContainerPort: pgPort,
+				Protocol:      v1.ProtocolTCP,
+			},
+		},
+		Env: envVars,
+	}
+
+	podTemplate := &v1.PodTemplateSpec{
+		ObjectMeta: metav1.ObjectMeta{
+			Labels:      c.connPoolLabelsSelector().MatchLabels,
+			Namespace:   c.Namespace,
+			Annotations: c.generatePodAnnotations(spec),
+		},
+		Spec: v1.PodSpec{
+			ServiceAccountName:            c.OpConfig.PodServiceAccountName,
+			TerminationGracePeriodSeconds: &gracePeriod,
+			Containers:                    []v1.Container{poolerContainer},
+			// TODO: add tolerations to scheduler pooler on the same node
+			// as database
+			//Tolerations:                   *tolerationsSpec,
+		},
+	}
+
+	return podTemplate, nil
+}
+
+// Return an array of ownerReferences to make an arbitraty object dependent on
+// the StatefulSet. Dependency is made on StatefulSet instead of PostgreSQL CRD
+// while the former is represent the actual state, and only it's deletion means
+// we delete the cluster (e.g. if CRD was deleted, StatefulSet somehow
+// survived, we can't delete an object because it will affect the functioning
+// cluster).
+func (c *Cluster) ownerReferences() []metav1.OwnerReference {
+	controller := true
+
+	if c.Statefulset == nil {
+		c.logger.Warning("Cannot get owner reference, no statefulset")
+		return []metav1.OwnerReference{}
+	}
+
+	return []metav1.OwnerReference{
+		{
+			UID:        c.Statefulset.ObjectMeta.UID,
+			APIVersion: "apps/v1",
+			Kind:       "StatefulSet",
+			Name:       c.Statefulset.ObjectMeta.Name,
+			Controller: &controller,
+		},
+	}
+}
+
+func (c *Cluster) generateConnPoolDeployment(spec *acidv1.PostgresSpec) (
+	*appsv1.Deployment, error) {
+
+	// there are two ways to enable connection pooler, either to specify a
+	// connectionPool section or enableConnectionPool. In the second case
+	// spec.connectionPool will be nil, so to make it easier to calculate
+	// default values, initialize it to an empty structure. It could be done
+	// anywhere, but here is the earliest common entry point between sync and
+	// create code, so init here.
+	if spec.ConnectionPool == nil {
+		spec.ConnectionPool = &acidv1.ConnectionPool{}
+	}
+
+	podTemplate, err := c.generateConnPoolPodTemplate(spec)
+	numberOfInstances := spec.ConnectionPool.NumberOfInstances
+	if numberOfInstances == nil {
+		numberOfInstances = util.CoalesceInt32(
+			c.OpConfig.ConnectionPool.NumberOfInstances,
+			k8sutil.Int32ToPointer(1))
+	}
+
+	if *numberOfInstances < constants.ConnPoolMinInstances {
+		msg := "Adjusted number of connection pool instances from %d to %d"
+		c.logger.Warningf(msg, numberOfInstances, constants.ConnPoolMinInstances)
+
+		*numberOfInstances = constants.ConnPoolMinInstances
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	deployment := &appsv1.Deployment{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:        c.connPoolName(),
+			Namespace:   c.Namespace,
+			Labels:      c.connPoolLabelsSelector().MatchLabels,
+			Annotations: map[string]string{},
+			// make StatefulSet object its owner to represent the dependency.
+			// By itself StatefulSet is being deleted with "Orphaned"
+			// propagation policy, which means that it's deletion will not
+			// clean up this deployment, but there is a hope that this object
+			// will be garbage collected if something went wrong and operator
+			// didn't deleted it.
+			OwnerReferences: c.ownerReferences(),
+		},
+		Spec: appsv1.DeploymentSpec{
+			Replicas: numberOfInstances,
+			Selector: c.connPoolLabelsSelector(),
+			Template: *podTemplate,
+		},
+	}
+
+	return deployment, nil
+}
+
+func (c *Cluster) generateConnPoolService(spec *acidv1.PostgresSpec) *v1.Service {
+
+	// there are two ways to enable connection pooler, either to specify a
+	// connectionPool section or enableConnectionPool. In the second case
+	// spec.connectionPool will be nil, so to make it easier to calculate
+	// default values, initialize it to an empty structure. It could be done
+	// anywhere, but here is the earliest common entry point between sync and
+	// create code, so init here.
+	if spec.ConnectionPool == nil {
+		spec.ConnectionPool = &acidv1.ConnectionPool{}
+	}
+
+	serviceSpec := v1.ServiceSpec{
+		Ports: []v1.ServicePort{
+			{
+				Name:       c.connPoolName(),
+				Port:       pgPort,
+				TargetPort: intstr.IntOrString{StrVal: c.servicePort(Master)},
+			},
+		},
+		Type: v1.ServiceTypeClusterIP,
+		Selector: map[string]string{
+			"connection-pool": c.connPoolName(),
+		},
+	}
+
+	service := &v1.Service{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:        c.connPoolName(),
+			Namespace:   c.Namespace,
+			Labels:      c.connPoolLabelsSelector().MatchLabels,
+			Annotations: map[string]string{},
+			// make StatefulSet object its owner to represent the dependency.
+			// By itself StatefulSet is being deleted with "Orphaned"
+			// propagation policy, which means that it's deletion will not
+			// clean up this service, but there is a hope that this object will
+			// be garbage collected if something went wrong and operator didn't
+			// deleted it.
+			OwnerReferences: c.ownerReferences(),
+		},
+		Spec: serviceSpec,
+	}
+
+	return service
+}
+
 func ensurePath(file string, defaultDir string, defaultFile string) string {
 	if file == "" {
 		return path.Join(defaultDir, defaultFile)

pkg/cluster/k8sres_test.go

@@ -1,6 +1,8 @@
 package cluster
 
 import (
+	"errors"
+	"fmt"
 	"reflect"
 
 	"testing"
@@ -13,6 +15,7 @@ import (
 	"github.com/zalando/postgres-operator/pkg/util/constants"
 	"github.com/zalando/postgres-operator/pkg/util/k8sutil"
 
+	appsv1 "k8s.io/api/apps/v1"
 	v1 "k8s.io/api/core/v1"
 	policyv1beta1 "k8s.io/api/policy/v1beta1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -582,6 +585,375 @@ func TestSecretVolume(t *testing.T) {
 	}
 }
 
+func testResources(cluster *Cluster, podSpec *v1.PodTemplateSpec) error {
+	cpuReq := podSpec.Spec.Containers[0].Resources.Requests["cpu"]
+	if cpuReq.String() != cluster.OpConfig.ConnectionPool.ConnPoolDefaultCPURequest {
+		return fmt.Errorf("CPU request doesn't match, got %s, expected %s",
+			cpuReq.String(), cluster.OpConfig.ConnectionPool.ConnPoolDefaultCPURequest)
+	}
+
+	memReq := podSpec.Spec.Containers[0].Resources.Requests["memory"]
+	if memReq.String() != cluster.OpConfig.ConnectionPool.ConnPoolDefaultMemoryRequest {
+		return fmt.Errorf("Memory request doesn't match, got %s, expected %s",
+			memReq.String(), cluster.OpConfig.ConnectionPool.ConnPoolDefaultMemoryRequest)
+	}
+
+	cpuLim := podSpec.Spec.Containers[0].Resources.Limits["cpu"]
+	if cpuLim.String() != cluster.OpConfig.ConnectionPool.ConnPoolDefaultCPULimit {
+		return fmt.Errorf("CPU limit doesn't match, got %s, expected %s",
+			cpuLim.String(), cluster.OpConfig.ConnectionPool.ConnPoolDefaultCPULimit)
+	}
+
+	memLim := podSpec.Spec.Containers[0].Resources.Limits["memory"]
+	if memLim.String() != cluster.OpConfig.ConnectionPool.ConnPoolDefaultMemoryLimit {
+		return fmt.Errorf("Memory limit doesn't match, got %s, expected %s",
+			memLim.String(), cluster.OpConfig.ConnectionPool.ConnPoolDefaultMemoryLimit)
+	}
+
+	return nil
+}
+
+func testLabels(cluster *Cluster, podSpec *v1.PodTemplateSpec) error {
+	poolLabels := podSpec.ObjectMeta.Labels["connection-pool"]
+
+	if poolLabels != cluster.connPoolLabelsSelector().MatchLabels["connection-pool"] {
+		return fmt.Errorf("Pod labels do not match, got %+v, expected %+v",
+			podSpec.ObjectMeta.Labels, cluster.connPoolLabelsSelector().MatchLabels)
+	}
+
+	return nil
+}
+
+func testEnvs(cluster *Cluster, podSpec *v1.PodTemplateSpec) error {
+	required := map[string]bool{
+		"PGHOST":               false,
+		"PGPORT":               false,
+		"PGUSER":               false,
+		"PGSCHEMA":             false,
+		"PGPASSWORD":           false,
+		"CONNECTION_POOL_MODE": false,
+		"CONNECTION_POOL_PORT": false,
+	}
+
+	envs := podSpec.Spec.Containers[0].Env
+	for _, env := range envs {
+		required[env.Name] = true
+	}
+
+	for env, value := range required {
+		if !value {
+			return fmt.Errorf("Environment variable %s is not present", env)
+		}
+	}
+
+	return nil
+}
+
+func testCustomPodTemplate(cluster *Cluster, podSpec *v1.PodTemplateSpec) error {
+	if podSpec.ObjectMeta.Name != "test-pod-template" {
+		return fmt.Errorf("Custom pod template is not used, current spec %+v",
+			podSpec)
+	}
+
+	return nil
+}
+
+func TestConnPoolPodSpec(t *testing.T) {
+	testName := "Test connection pool pod template generation"
+	var cluster = New(
+		Config{
+			OpConfig: config.Config{
+				ProtectedRoles: []string{"admin"},
+				Auth: config.Auth{
+					SuperUsername:       superUserName,
+					ReplicationUsername: replicationUserName,
+				},
+				ConnectionPool: config.ConnectionPool{
+					MaxDBConnections:             int32ToPointer(60),
+					ConnPoolDefaultCPURequest:    "100m",
+					ConnPoolDefaultCPULimit:      "100m",
+					ConnPoolDefaultMemoryRequest: "100Mi",
+					ConnPoolDefaultMemoryLimit:   "100Mi",
+				},
+			},
+		}, k8sutil.KubernetesClient{}, acidv1.Postgresql{}, logger)
+
+	var clusterNoDefaultRes = New(
+		Config{
+			OpConfig: config.Config{
+				ProtectedRoles: []string{"admin"},
+				Auth: config.Auth{
+					SuperUsername:       superUserName,
+					ReplicationUsername: replicationUserName,
+				},
+				ConnectionPool: config.ConnectionPool{},
+			},
+		}, k8sutil.KubernetesClient{}, acidv1.Postgresql{}, logger)
+
+	noCheck := func(cluster *Cluster, podSpec *v1.PodTemplateSpec) error { return nil }
+
+	tests := []struct {
+		subTest  string
+		spec     *acidv1.PostgresSpec
+		expected error
+		cluster  *Cluster
+		check    func(cluster *Cluster, podSpec *v1.PodTemplateSpec) error
+	}{
+		{
+			subTest: "default configuration",
+			spec: &acidv1.PostgresSpec{
+				ConnectionPool: &acidv1.ConnectionPool{},
+			},
+			expected: nil,
+			cluster:  cluster,
+			check:    noCheck,
+		},
+		{
+			subTest: "no default resources",
+			spec: &acidv1.PostgresSpec{
+				ConnectionPool: &acidv1.ConnectionPool{},
+			},
+			expected: errors.New(`could not generate resource requirements: could not fill resource requests: could not parse default CPU quantity: quantities must match the regular expression '^([+-]?[0-9.]+)([eEinumkKMGTP]*[-+]?[0-9]*)$'`),
+			cluster:  clusterNoDefaultRes,
+			check:    noCheck,
+		},
+		{
+			subTest: "default resources are set",
+			spec: &acidv1.PostgresSpec{
+				ConnectionPool: &acidv1.ConnectionPool{},
+			},
+			expected: nil,
+			cluster:  cluster,
+			check:    testResources,
+		},
+		{
+			subTest: "labels for service",
+			spec: &acidv1.PostgresSpec{
+				ConnectionPool: &acidv1.ConnectionPool{},
+			},
+			expected: nil,
+			cluster:  cluster,
+			check:    testLabels,
+		},
+		{
+			subTest: "required envs",
+			spec: &acidv1.PostgresSpec{
+				ConnectionPool: &acidv1.ConnectionPool{},
+			},
+			expected: nil,
+			cluster:  cluster,
+			check:    testEnvs,
+		},
+	}
+	for _, tt := range tests {
+		podSpec, err := tt.cluster.generateConnPoolPodTemplate(tt.spec)
+
+		if err != tt.expected && err.Error() != tt.expected.Error() {
+			t.Errorf("%s [%s]: Could not generate pod template,\n %+v, expected\n %+v",
+				testName, tt.subTest, err, tt.expected)
+		}
+
+		err = tt.check(cluster, podSpec)
+		if err != nil {
+			t.Errorf("%s [%s]: Pod spec is incorrect, %+v",
+				testName, tt.subTest, err)
+		}
+	}
+}
+
+func testDeploymentOwnwerReference(cluster *Cluster, deployment *appsv1.Deployment) error {
+	owner := deployment.ObjectMeta.OwnerReferences[0]
+
+	if owner.Name != cluster.Statefulset.ObjectMeta.Name {
+		return fmt.Errorf("Ownere reference is incorrect, got %s, expected %s",
+			owner.Name, cluster.Statefulset.ObjectMeta.Name)
+	}
+
+	return nil
+}
+
+func testSelector(cluster *Cluster, deployment *appsv1.Deployment) error {
+	labels := deployment.Spec.Selector.MatchLabels
+	expected := cluster.connPoolLabelsSelector().MatchLabels
+
+	if labels["connection-pool"] != expected["connection-pool"] {
+		return fmt.Errorf("Labels are incorrect, got %+v, expected %+v",
+			labels, expected)
+	}
+
+	return nil
+}
+
+func TestConnPoolDeploymentSpec(t *testing.T) {
+	testName := "Test connection pool deployment spec generation"
+	var cluster = New(
+		Config{
+			OpConfig: config.Config{
+				ProtectedRoles: []string{"admin"},
+				Auth: config.Auth{
+					SuperUsername:       superUserName,
+					ReplicationUsername: replicationUserName,
+				},
+				ConnectionPool: config.ConnectionPool{
+					ConnPoolDefaultCPURequest:    "100m",
+					ConnPoolDefaultCPULimit:      "100m",
+					ConnPoolDefaultMemoryRequest: "100Mi",
+					ConnPoolDefaultMemoryLimit:   "100Mi",
+				},
+			},
+		}, k8sutil.KubernetesClient{}, acidv1.Postgresql{}, logger)
+	cluster.Statefulset = &appsv1.StatefulSet{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-sts",
+		},
+	}
+
+	noCheck := func(cluster *Cluster, deployment *appsv1.Deployment) error {
+		return nil
+	}
+
+	tests := []struct {
+		subTest  string
+		spec     *acidv1.PostgresSpec
+		expected error
+		cluster  *Cluster
+		check    func(cluster *Cluster, deployment *appsv1.Deployment) error
+	}{
+		{
+			subTest: "default configuration",
+			spec: &acidv1.PostgresSpec{
+				ConnectionPool: &acidv1.ConnectionPool{},
+			},
+			expected: nil,
+			cluster:  cluster,
+			check:    noCheck,
+		},
+		{
+			subTest: "owner reference",
+			spec: &acidv1.PostgresSpec{
+				ConnectionPool: &acidv1.ConnectionPool{},
+			},
+			expected: nil,
+			cluster:  cluster,
+			check:    testDeploymentOwnwerReference,
+		},
+		{
+			subTest: "selector",
+			spec: &acidv1.PostgresSpec{
+				ConnectionPool: &acidv1.ConnectionPool{},
+			},
+			expected: nil,
+			cluster:  cluster,
+			check:    testSelector,
+		},
+	}
+	for _, tt := range tests {
+		deployment, err := tt.cluster.generateConnPoolDeployment(tt.spec)
+
+		if err != tt.expected && err.Error() != tt.expected.Error() {
+			t.Errorf("%s [%s]: Could not generate deployment spec,\n %+v, expected\n %+v",
+				testName, tt.subTest, err, tt.expected)
+		}
+
+		err = tt.check(cluster, deployment)
+		if err != nil {
+			t.Errorf("%s [%s]: Deployment spec is incorrect, %+v",
+				testName, tt.subTest, err)
+		}
+	}
+}
+
+func testServiceOwnwerReference(cluster *Cluster, service *v1.Service) error {
+	owner := service.ObjectMeta.OwnerReferences[0]
+
+	if owner.Name != cluster.Statefulset.ObjectMeta.Name {
+		return fmt.Errorf("Ownere reference is incorrect, got %s, expected %s",
+			owner.Name, cluster.Statefulset.ObjectMeta.Name)
+	}
+
+	return nil
+}
+
+func testServiceSelector(cluster *Cluster, service *v1.Service) error {
+	selector := service.Spec.Selector
+
+	if selector["connection-pool"] != cluster.connPoolName() {
+		return fmt.Errorf("Selector is incorrect, got %s, expected %s",
+			selector["connection-pool"], cluster.connPoolName())
+	}
+
+	return nil
+}
+
+func TestConnPoolServiceSpec(t *testing.T) {
+	testName := "Test connection pool service spec generation"
+	var cluster = New(
+		Config{
+			OpConfig: config.Config{
+				ProtectedRoles: []string{"admin"},
+				Auth: config.Auth{
+					SuperUsername:       superUserName,
+					ReplicationUsername: replicationUserName,
+				},
+				ConnectionPool: config.ConnectionPool{
+					ConnPoolDefaultCPURequest:    "100m",
+					ConnPoolDefaultCPULimit:      "100m",
+					ConnPoolDefaultMemoryRequest: "100Mi",
+					ConnPoolDefaultMemoryLimit:   "100Mi",
+				},
+			},
+		}, k8sutil.KubernetesClient{}, acidv1.Postgresql{}, logger)
+	cluster.Statefulset = &appsv1.StatefulSet{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-sts",
+		},
+	}
+
+	noCheck := func(cluster *Cluster, deployment *v1.Service) error {
+		return nil
+	}
+
+	tests := []struct {
+		subTest string
+		spec    *acidv1.PostgresSpec
+		cluster *Cluster
+		check   func(cluster *Cluster, deployment *v1.Service) error
+	}{
+		{
+			subTest: "default configuration",
+			spec: &acidv1.PostgresSpec{
+				ConnectionPool: &acidv1.ConnectionPool{},
+			},
+			cluster: cluster,
+			check:   noCheck,
+		},
+		{
+			subTest: "owner reference",
+			spec: &acidv1.PostgresSpec{
+				ConnectionPool: &acidv1.ConnectionPool{},
+			},
+			cluster: cluster,
+			check:   testServiceOwnwerReference,
+		},
+		{
+			subTest: "selector",
+			spec: &acidv1.PostgresSpec{
+				ConnectionPool: &acidv1.ConnectionPool{},
+			},
+			cluster: cluster,
+			check:   testServiceSelector,
+		},
+	}
+	for _, tt := range tests {
+		service := tt.cluster.generateConnPoolService(tt.spec)
+
+		if err := tt.check(cluster, service); err != nil {
+			t.Errorf("%s [%s]: Service spec is incorrect, %+v",
+				testName, tt.subTest, err)
+		}
+	}
+}
+
 func TestTLS(t *testing.T) {
 	var err error
 	var spec acidv1.PostgresSpec

pkg/cluster/resources.go

@@ -90,6 +90,132 @@ func (c *Cluster) createStatefulSet() (*appsv1.StatefulSet, error) {
 	return statefulSet, nil
 }
 
+// Prepare the database for connection pool to be used, i.e. install lookup
+// function (do it first, because it should be fast and if it didn't succeed,
+// it doesn't makes sense to create more K8S objects. At this moment we assume
+// that necessary connection pool user exists.
+//
+// After that create all the objects for connection pool, namely a deployment
+// with a chosen pooler and a service to expose it.
+func (c *Cluster) createConnectionPool(lookup InstallFunction) (*ConnectionPoolObjects, error) {
+	var msg string
+	c.setProcessName("creating connection pool")
+
+	schema := c.Spec.ConnectionPool.Schema
+	if schema == "" {
+		schema = c.OpConfig.ConnectionPool.Schema
+	}
+
+	user := c.Spec.ConnectionPool.User
+	if user == "" {
+		user = c.OpConfig.ConnectionPool.User
+	}
+
+	err := lookup(schema, user)
+
+	if err != nil {
+		msg = "could not prepare database for connection pool: %v"
+		return nil, fmt.Errorf(msg, err)
+	}
+
+	deploymentSpec, err := c.generateConnPoolDeployment(&c.Spec)
+	if err != nil {
+		msg = "could not generate deployment for connection pool: %v"
+		return nil, fmt.Errorf(msg, err)
+	}
+
+	// client-go does retry 10 times (with NoBackoff by default) when the API
+	// believe a request can be retried and returns Retry-After header. This
+	// should be good enough to not think about it here.
+	deployment, err := c.KubeClient.
+		Deployments(deploymentSpec.Namespace).
+		Create(deploymentSpec)
+
+	if err != nil {
+		return nil, err
+	}
+
+	serviceSpec := c.generateConnPoolService(&c.Spec)
+	service, err := c.KubeClient.
+		Services(serviceSpec.Namespace).
+		Create(serviceSpec)
+
+	if err != nil {
+		return nil, err
+	}
+
+	c.ConnectionPool = &ConnectionPoolObjects{
+		Deployment: deployment,
+		Service:    service,
+	}
+	c.logger.Debugf("created new connection pool %q, uid: %q",
+		util.NameFromMeta(deployment.ObjectMeta), deployment.UID)
+
+	return c.ConnectionPool, nil
+}
+
+func (c *Cluster) deleteConnectionPool() (err error) {
+	c.setProcessName("deleting connection pool")
+	c.logger.Debugln("deleting connection pool")
+
+	// Lack of connection pooler objects is not a fatal error, just log it if
+	// it was present before in the manifest
+	if c.ConnectionPool == nil {
+		c.logger.Infof("No connection pool to delete")
+		return nil
+	}
+
+	// Clean up the deployment object. If deployment resource we've remembered
+	// is somehow empty, try to delete based on what would we generate
+	deploymentName := c.connPoolName()
+	deployment := c.ConnectionPool.Deployment
+
+	if deployment != nil {
+		deploymentName = deployment.Name
+	}
+
+	// set delete propagation policy to foreground, so that replica set will be
+	// also deleted.
+	policy := metav1.DeletePropagationForeground
+	options := metav1.DeleteOptions{PropagationPolicy: &policy}
+	err = c.KubeClient.
+		Deployments(c.Namespace).
+		Delete(deploymentName, &options)
+
+	if !k8sutil.ResourceNotFound(err) {
+		c.logger.Debugf("Connection pool deployment was already deleted")
+	} else if err != nil {
+		return fmt.Errorf("could not delete deployment: %v", err)
+	}
+
+	c.logger.Infof("Connection pool deployment %q has been deleted", deploymentName)
+
+	// Repeat the same for the service object
+	service := c.ConnectionPool.Service
+	serviceName := c.connPoolName()
+
+	if service != nil {
+		serviceName = service.Name
+	}
+
+	// set delete propagation policy to foreground, so that all the dependant
+	// will be deleted.
+	err = c.KubeClient.
+		Services(c.Namespace).
+		Delete(serviceName, &options)
+
+	if !k8sutil.ResourceNotFound(err) {
+		c.logger.Debugf("Connection pool service was already deleted")
+	} else if err != nil {
+		return fmt.Errorf("could not delete service: %v", err)
+	}
+
+	c.logger.Infof("Connection pool service %q has been deleted", serviceName)
+
+	c.ConnectionPool = nil
+	return nil
+}
+
 func getPodIndex(podName string) (int32, error) {
 	parts := strings.Split(podName, "-")
 	if len(parts) == 0 {
@@ -674,3 +800,34 @@ func (c *Cluster) GetStatefulSet() *appsv1.StatefulSet {
 func (c *Cluster) GetPodDisruptionBudget() *policybeta1.PodDisruptionBudget {
 	return c.PodDisruptionBudget
 }
+
+// Perform actual patching of a connection pool deployment, assuming that all
+// the check were already done before.
+func (c *Cluster) updateConnPoolDeployment(oldDeploymentSpec, newDeployment *appsv1.Deployment) (*appsv1.Deployment, error) {
+	c.setProcessName("updating connection pool")
+	if c.ConnectionPool == nil || c.ConnectionPool.Deployment == nil {
+		return nil, fmt.Errorf("there is no connection pool in the cluster")
+	}
+
+	patchData, err := specPatch(newDeployment.Spec)
+	if err != nil {
+		return nil, fmt.Errorf("could not form patch for the deployment: %v", err)
+	}
+
+	// An update probably requires RetryOnConflict, but since only one operator
+	// worker at one time will try to update it chances of conflicts are
+	// minimal.
+	deployment, err := c.KubeClient.
+		Deployments(c.ConnectionPool.Deployment.Namespace).
+		Patch(
+			c.ConnectionPool.Deployment.Name,
+			types.MergePatchType,
+			patchData, "")
+	if err != nil {
+		return nil, fmt.Errorf("could not patch deployment: %v", err)
+	}
+
+	c.ConnectionPool.Deployment = deployment
+
+	return deployment, nil
+}

pkg/cluster/resources_test.go

@@ -0,0 +1,127 @@
+package cluster
+
+import (
+	"testing"
+
+	acidv1 "github.com/zalando/postgres-operator/pkg/apis/acid.zalan.do/v1"
+	"github.com/zalando/postgres-operator/pkg/util/config"
+	"github.com/zalando/postgres-operator/pkg/util/k8sutil"
+
+	appsv1 "k8s.io/api/apps/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+func mockInstallLookupFunction(schema string, user string) error {
+	return nil
+}
+
+func boolToPointer(value bool) *bool {
+	return &value
+}
+
+func TestConnPoolCreationAndDeletion(t *testing.T) {
+	testName := "Test connection pool creation"
+	var cluster = New(
+		Config{
+			OpConfig: config.Config{
+				ProtectedRoles: []string{"admin"},
+				Auth: config.Auth{
+					SuperUsername:       superUserName,
+					ReplicationUsername: replicationUserName,
+				},
+				ConnectionPool: config.ConnectionPool{
+					ConnPoolDefaultCPURequest:    "100m",
+					ConnPoolDefaultCPULimit:      "100m",
+					ConnPoolDefaultMemoryRequest: "100Mi",
+					ConnPoolDefaultMemoryLimit:   "100Mi",
+				},
+			},
+		}, k8sutil.NewMockKubernetesClient(), acidv1.Postgresql{}, logger)
+
+	cluster.Statefulset = &appsv1.StatefulSet{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-sts",
+		},
+	}
+
+	cluster.Spec = acidv1.PostgresSpec{
+		ConnectionPool: &acidv1.ConnectionPool{},
+	}
+	poolResources, err := cluster.createConnectionPool(mockInstallLookupFunction)
+
+	if err != nil {
+		t.Errorf("%s: Cannot create connection pool, %s, %+v",
+			testName, err, poolResources)
+	}
+
+	if poolResources.Deployment == nil {
+		t.Errorf("%s: Connection pool deployment is empty", testName)
+	}
+
+	if poolResources.Service == nil {
+		t.Errorf("%s: Connection pool service is empty", testName)
+	}
+
+	err = cluster.deleteConnectionPool()
+	if err != nil {
+		t.Errorf("%s: Cannot delete connection pool, %s", testName, err)
+	}
+}
+
+func TestNeedConnPool(t *testing.T) {
+	testName := "Test how connection pool can be enabled"
+	var cluster = New(
+		Config{
+			OpConfig: config.Config{
+				ProtectedRoles: []string{"admin"},
+				Auth: config.Auth{
+					SuperUsername:       superUserName,
+					ReplicationUsername: replicationUserName,
+				},
+				ConnectionPool: config.ConnectionPool{
+					ConnPoolDefaultCPURequest:    "100m",
+					ConnPoolDefaultCPULimit:      "100m",
+					ConnPoolDefaultMemoryRequest: "100Mi",
+					ConnPoolDefaultMemoryLimit:   "100Mi",
+				},
+			},
+		}, k8sutil.NewMockKubernetesClient(), acidv1.Postgresql{}, logger)
+
+	cluster.Spec = acidv1.PostgresSpec{
+		ConnectionPool: &acidv1.ConnectionPool{},
+	}
+
+	if !cluster.needConnectionPool() {
+		t.Errorf("%s: Connection pool is not enabled with full definition",
+			testName)
+	}
+
+	cluster.Spec = acidv1.PostgresSpec{
+		EnableConnectionPool: boolToPointer(true),
+	}
+
+	if !cluster.needConnectionPool() {
+		t.Errorf("%s: Connection pool is not enabled with flag",
+			testName)
+	}
+
+	cluster.Spec = acidv1.PostgresSpec{
+		EnableConnectionPool: boolToPointer(false),
+		ConnectionPool:       &acidv1.ConnectionPool{},
+	}
+
+	if cluster.needConnectionPool() {
+		t.Errorf("%s: Connection pool is still enabled with flag being false",
+			testName)
+	}
+
+	cluster.Spec = acidv1.PostgresSpec{
+		EnableConnectionPool: boolToPointer(true),
+		ConnectionPool:       &acidv1.ConnectionPool{},
+	}
+
+	if !cluster.needConnectionPool() {
+		t.Errorf("%s: Connection pool is not enabled with flag and full",
+			testName)
+	}
+}

pkg/cluster/sync.go

@@ -23,6 +23,7 @@ func (c *Cluster) Sync(newSpec *acidv1.Postgresql) error {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
+	oldSpec := c.Postgresql
 	c.setSpec(newSpec)
 
 	defer func() {
@@ -108,6 +109,11 @@ func (c *Cluster) Sync(newSpec *acidv1.Postgresql) error {
 		}
 	}
 
+	// sync connection pool
+	if err = c.syncConnectionPool(&oldSpec, newSpec, c.installLookupFunction); err != nil {
+		return fmt.Errorf("could not sync connection pool: %v", err)
+	}
+
 	return err
 }
 
@@ -424,7 +430,9 @@ func (c *Cluster) syncSecrets() error {
 			}
 			pwdUser := userMap[secretUsername]
 			// if this secret belongs to the infrastructure role and the password has changed - replace it in the secret
-			if pwdUser.Password != string(secret.Data["password"]) && pwdUser.Origin == spec.RoleOriginInfrastructure {
+			if pwdUser.Password != string(secret.Data["password"]) &&
+				pwdUser.Origin == spec.RoleOriginInfrastructure {
+
 				c.logger.Debugf("updating the secret %q from the infrastructure roles", secretSpec.Name)
 				if _, err = c.KubeClient.Secrets(secretSpec.Namespace).Update(secretSpec); err != nil {
 					return fmt.Errorf("could not update infrastructure role secret for role %q: %v", secretUsername, err)
@@ -468,6 +476,16 @@ func (c *Cluster) syncRoles() (err error) {
 	for _, u := range c.pgUsers {
 		userNames = append(userNames, u.Name)
 	}
+
+	if c.needConnectionPool() {
+		connPoolUser := c.systemUsers[constants.ConnectionPoolUserKeyName]
+		userNames = append(userNames, connPoolUser.Name)
+
+		if _, exists := c.pgUsers[connPoolUser.Name]; !exists {
+			c.pgUsers[connPoolUser.Name] = connPoolUser
+		}
+	}
+
 	dbUsers, err = c.readPgUsersFromDatabase(userNames)
 	if err != nil {
 		return fmt.Errorf("error getting users from the database: %v", err)
@@ -600,3 +618,165 @@ func (c *Cluster) syncLogicalBackupJob() error {
 
 	return nil
 }
+
+func (c *Cluster) syncConnectionPool(oldSpec, newSpec *acidv1.Postgresql, lookup InstallFunction) error {
+	if c.ConnectionPool == nil {
+		c.ConnectionPool = &ConnectionPoolObjects{}
+	}
+
+	newNeedConnPool := c.needConnectionPoolWorker(&newSpec.Spec)
+	oldNeedConnPool := c.needConnectionPoolWorker(&oldSpec.Spec)
+
+	if newNeedConnPool {
+		// Try to sync in any case. If we didn't needed connection pool before,
+		// it means we want to create it. If it was already present, still sync
+		// since it could happen that there is no difference in specs, and all
+		// the resources are remembered, but the deployment was manualy deleted
+		// in between
+		c.logger.Debug("syncing connection pool")
+
+		// in this case also do not forget to install lookup function as for
+		// creating cluster
+		if !oldNeedConnPool || !c.ConnectionPool.LookupFunction {
+			newConnPool := newSpec.Spec.ConnectionPool
+
+			specSchema := ""
+			specUser := ""
+
+			if newConnPool != nil {
+				specSchema = newConnPool.Schema
+				specUser = newConnPool.User
+			}
+
+			schema := util.Coalesce(
+				specSchema,
+				c.OpConfig.ConnectionPool.Schema)
+
+			user := util.Coalesce(
+				specUser,
+				c.OpConfig.ConnectionPool.User)
+
+			if err := lookup(schema, user); err != nil {
+				return err
+			}
+		}
+
+		if err := c.syncConnectionPoolWorker(oldSpec, newSpec); err != nil {
+			c.logger.Errorf("could not sync connection pool: %v", err)
+			return err
+		}
+	}
+
+	if oldNeedConnPool && !newNeedConnPool {
+		// delete and cleanup resources
+		if err := c.deleteConnectionPool(); err != nil {
+			c.logger.Warningf("could not remove connection pool: %v", err)
+		}
+	}
+
+	if !oldNeedConnPool && !newNeedConnPool {
+		// delete and cleanup resources if not empty
+		if c.ConnectionPool != nil &&
+			(c.ConnectionPool.Deployment != nil ||
+				c.ConnectionPool.Service != nil) {
+
+			if err := c.deleteConnectionPool(); err != nil {
+				c.logger.Warningf("could not remove connection pool: %v", err)
+			}
+		}
+	}
+
+	return nil
+}
+
+// Synchronize connection pool resources. Effectively we're interested only in
+// synchronizing the corresponding deployment, but in case of deployment or
+// service is missing, create it. After checking, also remember an object for
+// the future references.
+func (c *Cluster) syncConnectionPoolWorker(oldSpec, newSpec *acidv1.Postgresql) error {
+	deployment, err := c.KubeClient.
+		Deployments(c.Namespace).
+		Get(c.connPoolName(), metav1.GetOptions{})
+
+	if err != nil && k8sutil.ResourceNotFound(err) {
+		msg := "Deployment %s for connection pool synchronization is not found, create it"
+		c.logger.Warningf(msg, c.connPoolName())
+
+		deploymentSpec, err := c.generateConnPoolDeployment(&newSpec.Spec)
+		if err != nil {
+			msg = "could not generate deployment for connection pool: %v"
+			return fmt.Errorf(msg, err)
+		}
+
+		deployment, err := c.KubeClient.
+			Deployments(deploymentSpec.Namespace).
+			Create(deploymentSpec)
+
+		if err != nil {
+			return err
+		}
+
+		c.ConnectionPool.Deployment = deployment
+	} else if err != nil {
+		return fmt.Errorf("could not get connection pool deployment to sync: %v", err)
+	} else {
+		c.ConnectionPool.Deployment = deployment
+
+		// actual synchronization
+		oldConnPool := oldSpec.Spec.ConnectionPool
+		newConnPool := newSpec.Spec.ConnectionPool
+		specSync, specReason := c.needSyncConnPoolSpecs(oldConnPool, newConnPool)
+		defaultsSync, defaultsReason := c.needSyncConnPoolDefaults(newConnPool, deployment)
+		reason := append(specReason, defaultsReason...)
+		if specSync || defaultsSync {
+			c.logger.Infof("Update connection pool deployment %s, reason: %+v",
+				c.connPoolName(), reason)
+
+			newDeploymentSpec, err := c.generateConnPoolDeployment(&newSpec.Spec)
+			if err != nil {
+				msg := "could not generate deployment for connection pool: %v"
+				return fmt.Errorf(msg, err)
+			}
+
+			oldDeploymentSpec := c.ConnectionPool.Deployment
+
+			deployment, err := c.updateConnPoolDeployment(
+				oldDeploymentSpec,
+				newDeploymentSpec)
+
+			if err != nil {
+				return err
+			}
+
+			c.ConnectionPool.Deployment = deployment
+			return nil
+		}
+	}
+
+	service, err := c.KubeClient.
+		Services(c.Namespace).
+		Get(c.connPoolName(), metav1.GetOptions{})
+
+	if err != nil && k8sutil.ResourceNotFound(err) {
+		msg := "Service %s for connection pool synchronization is not found, create it"
+		c.logger.Warningf(msg, c.connPoolName())
+
+		serviceSpec := c.generateConnPoolService(&newSpec.Spec)
+		service, err := c.KubeClient.
+			Services(serviceSpec.Namespace).
+			Create(serviceSpec)
+
+		if err != nil {
+			return err
+		}
+
+		c.ConnectionPool.Service = service
+	} else if err != nil {
+		return fmt.Errorf("could not get connection pool service to sync: %v", err)
+	} else {
+		// Service updates are not supported and probably not that useful anyway
+		c.ConnectionPool.Service = service
+	}
+
+	return nil
+}

pkg/cluster/sync_test.go

@@ -0,0 +1,212 @@
+package cluster
+
+import (
+	"fmt"
+	"testing"
+
+	acidv1 "github.com/zalando/postgres-operator/pkg/apis/acid.zalan.do/v1"
+	"github.com/zalando/postgres-operator/pkg/util/config"
+	"github.com/zalando/postgres-operator/pkg/util/k8sutil"
+
+	appsv1 "k8s.io/api/apps/v1"
+	v1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+func int32ToPointer(value int32) *int32 {
+	return &value
+}
+
+func deploymentUpdated(cluster *Cluster, err error) error {
+	if cluster.ConnectionPool.Deployment.Spec.Replicas == nil ||
+		*cluster.ConnectionPool.Deployment.Spec.Replicas != 2 {
+		return fmt.Errorf("Wrong nubmer of instances")
+	}
+
+	return nil
+}
+
+func objectsAreSaved(cluster *Cluster, err error) error {
+	if cluster.ConnectionPool == nil {
+		return fmt.Errorf("Connection pool resources are empty")
+	}
+
+	if cluster.ConnectionPool.Deployment == nil {
+		return fmt.Errorf("Deployment was not saved")
+	}
+
+	if cluster.ConnectionPool.Service == nil {
+		return fmt.Errorf("Service was not saved")
+	}
+
+	return nil
+}
+
+func objectsAreDeleted(cluster *Cluster, err error) error {
+	if cluster.ConnectionPool != nil {
+		return fmt.Errorf("Connection pool was not deleted")
+	}
+
+	return nil
+}
+
+func TestConnPoolSynchronization(t *testing.T) {
+	testName := "Test connection pool synchronization"
+	var cluster = New(
+		Config{
+			OpConfig: config.Config{
+				ProtectedRoles: []string{"admin"},
+				Auth: config.Auth{
+					SuperUsername:       superUserName,
+					ReplicationUsername: replicationUserName,
+				},
+				ConnectionPool: config.ConnectionPool{
+					ConnPoolDefaultCPURequest:    "100m",
+					ConnPoolDefaultCPULimit:      "100m",
+					ConnPoolDefaultMemoryRequest: "100Mi",
+					ConnPoolDefaultMemoryLimit:   "100Mi",
+					NumberOfInstances:            int32ToPointer(1),
+				},
+			},
+		}, k8sutil.KubernetesClient{}, acidv1.Postgresql{}, logger)
+
+	cluster.Statefulset = &appsv1.StatefulSet{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-sts",
+		},
+	}
+
+	clusterMissingObjects := *cluster
+	clusterMissingObjects.KubeClient = k8sutil.ClientMissingObjects()
+
+	clusterMock := *cluster
+	clusterMock.KubeClient = k8sutil.NewMockKubernetesClient()
+
+	clusterDirtyMock := *cluster
+	clusterDirtyMock.KubeClient = k8sutil.NewMockKubernetesClient()
+	clusterDirtyMock.ConnectionPool = &ConnectionPoolObjects{
+		Deployment: &appsv1.Deployment{},
+		Service:    &v1.Service{},
+	}
+
+	clusterNewDefaultsMock := *cluster
+	clusterNewDefaultsMock.KubeClient = k8sutil.NewMockKubernetesClient()
+	cluster.OpConfig.ConnectionPool.Image = "pooler:2.0"
+	cluster.OpConfig.ConnectionPool.NumberOfInstances = int32ToPointer(2)
+
+	tests := []struct {
+		subTest string
+		oldSpec *acidv1.Postgresql
+		newSpec *acidv1.Postgresql
+		cluster *Cluster
+		check   func(cluster *Cluster, err error) error
+	}{
+		{
+			subTest: "create if doesn't exist",
+			oldSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{
+					ConnectionPool: &acidv1.ConnectionPool{},
+				},
+			},
+			newSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{
+					ConnectionPool: &acidv1.ConnectionPool{},
+				},
+			},
+			cluster: &clusterMissingObjects,
+			check:   objectsAreSaved,
+		},
+		{
+			subTest: "create if doesn't exist with a flag",
+			oldSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{},
+			},
+			newSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{
+					EnableConnectionPool: boolToPointer(true),
+				},
+			},
+			cluster: &clusterMissingObjects,
+			check:   objectsAreSaved,
+		},
+		{
+			subTest: "create from scratch",
+			oldSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{},
+			},
+			newSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{
+					ConnectionPool: &acidv1.ConnectionPool{},
+				},
+			},
+			cluster: &clusterMissingObjects,
+			check:   objectsAreSaved,
+		},
+		{
+			subTest: "delete if not needed",
+			oldSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{
+					ConnectionPool: &acidv1.ConnectionPool{},
+				},
+			},
+			newSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{},
+			},
+			cluster: &clusterMock,
+			check:   objectsAreDeleted,
+		},
+		{
+			subTest: "cleanup if still there",
+			oldSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{},
+			},
+			newSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{},
+			},
+			cluster: &clusterDirtyMock,
+			check:   objectsAreDeleted,
+		},
+		{
+			subTest: "update deployment",
+			oldSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{
+					ConnectionPool: &acidv1.ConnectionPool{
+						NumberOfInstances: int32ToPointer(1),
+					},
+				},
+			},
+			newSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{
+					ConnectionPool: &acidv1.ConnectionPool{
+						NumberOfInstances: int32ToPointer(2),
+					},
+				},
+			},
+			cluster: &clusterMock,
+			check:   deploymentUpdated,
+		},
+		{
+			subTest: "update image from changed defaults",
+			oldSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{
+					ConnectionPool: &acidv1.ConnectionPool{},
+				},
+			},
+			newSpec: &acidv1.Postgresql{
+				Spec: acidv1.PostgresSpec{
+					ConnectionPool: &acidv1.ConnectionPool{},
+				},
+			},
+			cluster: &clusterNewDefaultsMock,
+			check:   deploymentUpdated,
+		},
+	}
+	for _, tt := range tests {
+		err := tt.cluster.syncConnectionPool(tt.oldSpec, tt.newSpec, mockInstallLookupFunction)
+
+		if err := tt.check(tt.cluster, err); err != nil {
+			t.Errorf("%s [%s]: Could not synchronize, %+v",
+				testName, tt.subTest, err)
+		}
+	}
+}

pkg/cluster/types.go

@@ -69,3 +69,7 @@ type ClusterStatus struct {
 	Spec           acidv1.PostgresSpec
 	Error          error
 }
+
+type TemplateParams map[string]interface{}
+
+type InstallFunction func(schema string, user string) error

pkg/cluster/util.go

@@ -408,7 +408,32 @@ func (c *Cluster) labelsSet(shouldAddExtraLabels bool) labels.Set {
 }
 
 func (c *Cluster) labelsSelector() *metav1.LabelSelector {
-	return &metav1.LabelSelector{MatchLabels: c.labelsSet(false), MatchExpressions: nil}
+	return &metav1.LabelSelector{
+		MatchLabels:      c.labelsSet(false),
+		MatchExpressions: nil,
+	}
+}
+
+// Return connection pool labels selector, which should from one point of view
+// inherit most of the labels from the cluster itself, but at the same time
+// have e.g. different `application` label, so that recreatePod operation will
+// not interfere with it (it lists all the pods via labels, and if there would
+// be no difference, it will recreate also pooler pods).
+func (c *Cluster) connPoolLabelsSelector() *metav1.LabelSelector {
+	connPoolLabels := labels.Set(map[string]string{})
+
+	extraLabels := labels.Set(map[string]string{
+		"connection-pool": c.connPoolName(),
+		"application":     "db-connection-pool",
+	})
+
+	connPoolLabels = labels.Merge(connPoolLabels, c.labelsSet(false))
+	connPoolLabels = labels.Merge(connPoolLabels, extraLabels)
+
+	return &metav1.LabelSelector{
+		MatchLabels:      connPoolLabels,
+		MatchExpressions: nil,
+	}
 }
 
 func (c *Cluster) roleLabelsSet(shouldAddExtraLabels bool, role PostgresRole) labels.Set {
@@ -483,3 +508,15 @@ func (c *Cluster) GetSpec() (*acidv1.Postgresql, error) {
 func (c *Cluster) patroniUsesKubernetes() bool {
 	return c.OpConfig.EtcdHost == ""
 }
+
+func (c *Cluster) needConnectionPoolWorker(spec *acidv1.PostgresSpec) bool {
+	if spec.EnableConnectionPool == nil {
+		return spec.ConnectionPool != nil
+	} else {
+		return *spec.EnableConnectionPool
+	}
+}
+
+func (c *Cluster) needConnectionPool() bool {
+	return c.needConnectionPoolWorker(&c.Spec)
+}

pkg/controller/operator_config.go

@@ -8,6 +8,7 @@ import (
 	acidv1 "github.com/zalando/postgres-operator/pkg/apis/acid.zalan.do/v1"
 	"github.com/zalando/postgres-operator/pkg/util"
 	"github.com/zalando/postgres-operator/pkg/util/config"
+	"github.com/zalando/postgres-operator/pkg/util/constants"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
 
@@ -21,6 +22,10 @@ func (c *Controller) readOperatorConfigurationFromCRD(configObjectNamespace, con
 	return config, nil
 }
 
+func int32ToPointer(value int32) *int32 {
+	return &value
+}
+
 // importConfigurationFromCRD is a transitional function that converts CRD configuration to the one based on the configmap
 func (c *Controller) importConfigurationFromCRD(fromCRD *acidv1.OperatorConfigurationData) *config.Config {
 	result := &config.Config{}
@@ -143,5 +148,51 @@ func (c *Controller) importConfigurationFromCRD(fromCRD *acidv1.OperatorConfigur
 	result.ScalyrCPULimit = fromCRD.Scalyr.ScalyrCPULimit
 	result.ScalyrMemoryLimit = fromCRD.Scalyr.ScalyrMemoryLimit
 
+	// Connection pool. Looks like we can't use defaulting in CRD before 1.17,
+	// so ensure default values here.
+	result.ConnectionPool.NumberOfInstances = util.CoalesceInt32(
+		fromCRD.ConnectionPool.NumberOfInstances,
+		int32ToPointer(2))
+
+	result.ConnectionPool.NumberOfInstances = util.MaxInt32(
+		result.ConnectionPool.NumberOfInstances,
+		int32ToPointer(2))
+
+	result.ConnectionPool.Schema = util.Coalesce(
+		fromCRD.ConnectionPool.Schema,
+		constants.ConnectionPoolSchemaName)
+
+	result.ConnectionPool.User = util.Coalesce(
+		fromCRD.ConnectionPool.User,
+		constants.ConnectionPoolUserName)
+
+	result.ConnectionPool.Image = util.Coalesce(
+		fromCRD.ConnectionPool.Image,
+		"registry.opensource.zalan.do/acid/pgbouncer")
+
+	result.ConnectionPool.Mode = util.Coalesce(
+		fromCRD.ConnectionPool.Mode,
+		constants.ConnectionPoolDefaultMode)
+
+	result.ConnectionPool.ConnPoolDefaultCPURequest = util.Coalesce(
+		fromCRD.ConnectionPool.DefaultCPURequest,
+		constants.ConnectionPoolDefaultCpuRequest)
+
+	result.ConnectionPool.ConnPoolDefaultMemoryRequest = util.Coalesce(
+		fromCRD.ConnectionPool.DefaultMemoryRequest,
+		constants.ConnectionPoolDefaultMemoryRequest)
+
+	result.ConnectionPool.ConnPoolDefaultCPULimit = util.Coalesce(
+		fromCRD.ConnectionPool.DefaultCPULimit,
+		constants.ConnectionPoolDefaultCpuLimit)
+
+	result.ConnectionPool.ConnPoolDefaultMemoryLimit = util.Coalesce(
+		fromCRD.ConnectionPool.DefaultMemoryLimit,
+		constants.ConnectionPoolDefaultMemoryLimit)
+
+	result.ConnectionPool.MaxDBConnections = util.CoalesceInt32(
+		fromCRD.ConnectionPool.MaxDBConnections,
+		int32ToPointer(constants.ConnPoolMaxDBConnections))
+
 	return result
 }

pkg/spec/types.go

@@ -23,13 +23,15 @@ const fileWithNamespace = "/var/run/secrets/kubernetes.io/serviceaccount/namespa
 // RoleOrigin contains the code of the origin of a role
 type RoleOrigin int
 
-// The rolesOrigin constant values must be sorted by the role priority for resolveNameConflict(...) to work.
+// The rolesOrigin constant values must be sorted by the role priority for
+// resolveNameConflict(...) to work.
 const (
 	RoleOriginUnknown RoleOrigin = iota
 	RoleOriginManifest
 	RoleOriginInfrastructure
 	RoleOriginTeamsAPI
 	RoleOriginSystem
+	RoleConnectionPool
 )
 
 type syncUserOperation int
@@ -178,6 +180,8 @@ func (r RoleOrigin) String() string {
 		return "teams API role"
 	case RoleOriginSystem:
 		return "system role"
+	case RoleConnectionPool:
+		return "connection pool role"
 	default:
 		panic(fmt.Sprintf("bogus role origin value %d", r))
 	}

pkg/util/config/config.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 
 	"github.com/zalando/postgres-operator/pkg/spec"
+	"github.com/zalando/postgres-operator/pkg/util/constants"
 )
 
 // CRD describes CustomResourceDefinition specific configuration parameters
@@ -83,6 +84,20 @@ type LogicalBackup struct {
 	LogicalBackupS3SSE             string `name:"logical_backup_s3_sse" default:"AES256"`
 }
 
+// Operator options for connection pooler
+type ConnectionPool struct {
+	NumberOfInstances            *int32 `name:"connection_pool_number_of_instances" default:"2"`
+	Schema                       string `name:"connection_pool_schema" default:"pooler"`
+	User                         string `name:"connection_pool_user" default:"pooler"`
+	Image                        string `name:"connection_pool_image" default:"registry.opensource.zalan.do/acid/pgbouncer"`
+	Mode                         string `name:"connection_pool_mode" default:"transaction"`
+	MaxDBConnections             *int32 `name:"connection_pool_max_db_connections" default:"60"`
+	ConnPoolDefaultCPURequest    string `name:"connection_pool_default_cpu_request" default:"500m"`
+	ConnPoolDefaultMemoryRequest string `name:"connection_pool_default_memory_request" default:"100Mi"`
+	ConnPoolDefaultCPULimit      string `name:"connection_pool_default_cpu_limit" default:"1"`
+	ConnPoolDefaultMemoryLimit   string `name:"connection_pool_default_memory_limit" default:"100Mi"`
+}
+
 // Config describes operator config
 type Config struct {
 	CRD
@@ -90,6 +105,7 @@ type Config struct {
 	Auth
 	Scalyr
 	LogicalBackup
+	ConnectionPool
 
 	WatchedNamespace      string            `name:"watched_namespace"`    // special values: "*" means 'watch all namespaces', the empty string "" means 'watch a namespace where operator is deployed to'
 	EtcdHost              string            `name:"etcd_host" default:""` // special values: the empty string "" means Patroni will use K8s as a DCS
@@ -196,5 +212,10 @@ func validate(cfg *Config) (err error) {
 	if cfg.Workers == 0 {
 		err = fmt.Errorf("number of workers should be higher than 0")
 	}
+
+	if *cfg.ConnectionPool.NumberOfInstances < constants.ConnPoolMinInstances {
+		msg := "number of connection pool instances should be higher than %d"
+		err = fmt.Errorf(msg, constants.ConnPoolMinInstances)
+	}
 	return
 }

pkg/util/constants/pooler.go

@@ -0,0 +1,18 @@
+package constants
+
+// Connection pool specific constants
+const (
+	ConnectionPoolUserName             = "pooler"
+	ConnectionPoolSchemaName           = "pooler"
+	ConnectionPoolDefaultType          = "pgbouncer"
+	ConnectionPoolDefaultMode          = "transaction"
+	ConnectionPoolDefaultCpuRequest    = "500m"
+	ConnectionPoolDefaultCpuLimit      = "1"
+	ConnectionPoolDefaultMemoryRequest = "100Mi"
+	ConnectionPoolDefaultMemoryLimit   = "100Mi"
+
+	ConnPoolContainer            = 0
+	ConnPoolMaxDBConnections     = 60
+	ConnPoolMaxClientConnections = 10000
+	ConnPoolMinInstances         = 2
+)

pkg/util/constants/roles.go

@@ -4,6 +4,7 @@ package constants
 const (
 	PasswordLength            = 64
 	SuperuserKeyName          = "superuser"
+	ConnectionPoolUserKeyName = "pooler"
 	ReplicationUserKeyName    = "replication"
 	RoleFlagSuperuser         = "SUPERUSER"
 	RoleFlagInherit           = "INHERIT"

pkg/util/k8sutil/k8sutil.go

@@ -9,11 +9,13 @@ import (
 	batchv1beta1 "k8s.io/api/batch/v1beta1"
 	clientbatchv1beta1 "k8s.io/client-go/kubernetes/typed/batch/v1beta1"
 
+	apiappsv1 "k8s.io/api/apps/v1"
 	v1 "k8s.io/api/core/v1"
 	policybeta1 "k8s.io/api/policy/v1beta1"
 	apiextclient "k8s.io/apiextensions-apiserver/pkg/client/clientset/clientset"
 	apiextbeta1 "k8s.io/apiextensions-apiserver/pkg/client/clientset/clientset/typed/apiextensions/v1beta1"
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
+	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/client-go/kubernetes"
 	appsv1 "k8s.io/client-go/kubernetes/typed/apps/v1"
 	corev1 "k8s.io/client-go/kubernetes/typed/core/v1"
@@ -26,6 +28,10 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
 
+func Int32ToPointer(value int32) *int32 {
+	return &value
+}
+
 // KubernetesClient describes getters for Kubernetes objects
 type KubernetesClient struct {
 	corev1.SecretsGetter
@@ -39,6 +45,7 @@ type KubernetesClient struct {
 	corev1.NamespacesGetter
 	corev1.ServiceAccountsGetter
 	appsv1.StatefulSetsGetter
+	appsv1.DeploymentsGetter
 	rbacv1.RoleBindingsGetter
 	policyv1beta1.PodDisruptionBudgetsGetter
 	apiextbeta1.CustomResourceDefinitionsGetter
@@ -55,6 +62,34 @@ type mockSecret struct {
 type MockSecretGetter struct {
 }
 
+type mockDeployment struct {
+	appsv1.DeploymentInterface
+}
+
+type mockDeploymentNotExist struct {
+	appsv1.DeploymentInterface
+}
+
+type MockDeploymentGetter struct {
+}
+
+type MockDeploymentNotExistGetter struct {
+}
+
+type mockService struct {
+	corev1.ServiceInterface
+}
+
+type mockServiceNotExist struct {
+	corev1.ServiceInterface
+}
+
+type MockServiceGetter struct {
+}
+
+type MockServiceNotExistGetter struct {
+}
+
 type mockConfigMap struct {
 	corev1.ConfigMapInterface
 }
@@ -101,6 +136,7 @@ func NewFromConfig(cfg *rest.Config) (KubernetesClient, error) {
 	kubeClient.NodesGetter = client.CoreV1()
 	kubeClient.NamespacesGetter = client.CoreV1()
 	kubeClient.StatefulSetsGetter = client.AppsV1()
+	kubeClient.DeploymentsGetter = client.AppsV1()
 	kubeClient.PodDisruptionBudgetsGetter = client.PolicyV1beta1()
 	kubeClient.RESTClient = client.CoreV1().RESTClient()
 	kubeClient.RoleBindingsGetter = client.RbacV1()
@@ -230,19 +266,145 @@ func (c *mockConfigMap) Get(name string, options metav1.GetOptions) (*v1.ConfigM
 }
 
 // Secrets to be mocked
-func (c *MockSecretGetter) Secrets(namespace string) corev1.SecretInterface {
+func (mock *MockSecretGetter) Secrets(namespace string) corev1.SecretInterface {
 	return &mockSecret{}
 }
 
 // ConfigMaps to be mocked
-func (c *MockConfigMapsGetter) ConfigMaps(namespace string) corev1.ConfigMapInterface {
+func (mock *MockConfigMapsGetter) ConfigMaps(namespace string) corev1.ConfigMapInterface {
 	return &mockConfigMap{}
 }
 
+func (mock *MockDeploymentGetter) Deployments(namespace string) appsv1.DeploymentInterface {
+	return &mockDeployment{}
+}
+
+func (mock *MockDeploymentNotExistGetter) Deployments(namespace string) appsv1.DeploymentInterface {
+	return &mockDeploymentNotExist{}
+}
+
+func (mock *mockDeployment) Create(*apiappsv1.Deployment) (*apiappsv1.Deployment, error) {
+	return &apiappsv1.Deployment{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-deployment",
+		},
+		Spec: apiappsv1.DeploymentSpec{
+			Replicas: Int32ToPointer(1),
+		},
+	}, nil
+}
+
+func (mock *mockDeployment) Delete(name string, opts *metav1.DeleteOptions) error {
+	return nil
+}
+
+func (mock *mockDeployment) Get(name string, opts metav1.GetOptions) (*apiappsv1.Deployment, error) {
+	return &apiappsv1.Deployment{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-deployment",
+		},
+		Spec: apiappsv1.DeploymentSpec{
+			Replicas: Int32ToPointer(1),
+			Template: v1.PodTemplateSpec{
+				Spec: v1.PodSpec{
+					Containers: []v1.Container{
+						v1.Container{
+							Image: "pooler:1.0",
+						},
+					},
+				},
+			},
+		},
+	}, nil
+}
+
+func (mock *mockDeployment) Patch(name string, t types.PatchType, data []byte, subres ...string) (*apiappsv1.Deployment, error) {
+	return &apiappsv1.Deployment{
+		Spec: apiappsv1.DeploymentSpec{
+			Replicas: Int32ToPointer(2),
+		},
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-deployment",
+		},
+	}, nil
+}
+
+func (mock *mockDeploymentNotExist) Get(name string, opts metav1.GetOptions) (*apiappsv1.Deployment, error) {
+	return nil, &apierrors.StatusError{
+		ErrStatus: metav1.Status{
+			Reason: metav1.StatusReasonNotFound,
+		},
+	}
+}
+
+func (mock *mockDeploymentNotExist) Create(*apiappsv1.Deployment) (*apiappsv1.Deployment, error) {
+	return &apiappsv1.Deployment{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-deployment",
+		},
+		Spec: apiappsv1.DeploymentSpec{
+			Replicas: Int32ToPointer(1),
+		},
+	}, nil
+}
+
+func (mock *MockServiceGetter) Services(namespace string) corev1.ServiceInterface {
+	return &mockService{}
+}
+
+func (mock *MockServiceNotExistGetter) Services(namespace string) corev1.ServiceInterface {
+	return &mockServiceNotExist{}
+}
+
+func (mock *mockService) Create(*v1.Service) (*v1.Service, error) {
+	return &v1.Service{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-service",
+		},
+	}, nil
+}
+
+func (mock *mockService) Delete(name string, opts *metav1.DeleteOptions) error {
+	return nil
+}
+
+func (mock *mockService) Get(name string, opts metav1.GetOptions) (*v1.Service, error) {
+	return &v1.Service{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-service",
+		},
+	}, nil
+}
+
+func (mock *mockServiceNotExist) Create(*v1.Service) (*v1.Service, error) {
+	return &v1.Service{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-service",
+		},
+	}, nil
+}
+
+func (mock *mockServiceNotExist) Get(name string, opts metav1.GetOptions) (*v1.Service, error) {
+	return nil, &apierrors.StatusError{
+		ErrStatus: metav1.Status{
+			Reason: metav1.StatusReasonNotFound,
+		},
+	}
+}
+
 // NewMockKubernetesClient for other tests
 func NewMockKubernetesClient() KubernetesClient {
 	return KubernetesClient{
 		SecretsGetter:     &MockSecretGetter{},
 		ConfigMapsGetter:  &MockConfigMapsGetter{},
+		DeploymentsGetter: &MockDeploymentGetter{},
+		ServicesGetter:    &MockServiceGetter{},
+	}
+}
+
+func ClientMissingObjects() KubernetesClient {
+	return KubernetesClient{
+		DeploymentsGetter: &MockDeploymentNotExistGetter{},
+		ServicesGetter:    &MockServiceNotExistGetter{},
 	}
 }

pkg/util/util.go

@@ -147,6 +147,40 @@ func Coalesce(val, defaultVal string) string {
 	return val
 }
 
+// Yeah, golang
+func CoalesceInt32(val, defaultVal *int32) *int32 {
+	if val == nil {
+		return defaultVal
+	}
+	return val
+}
+
+// Test if any of the values is nil
+func testNil(values ...*int32) bool {
+	for _, v := range values {
+		if v == nil {
+			return true
+		}
+	}
+
+	return false
+}
+
+// Return maximum of two integers provided via pointers. If one value is not
+// defined, return the other one. If both are not defined, result is also
+// undefined, caller needs to check for that.
+func MaxInt32(a, b *int32) *int32 {
+	if testNil(a, b) {
+		return nil
+	}
+
+	if *a > *b {
+		return a
+	}
+
+	return b
+}
+
 // IsSmallerQuantity : checks if first resource is of a smaller quantity than the second
 func IsSmallerQuantity(requestStr, limitStr string) (bool, error) {
 

ui/manifests/deployment.yaml

@@ -20,7 +20,7 @@ spec:
       serviceAccountName: postgres-operator-ui
       containers:
         - name: "service"
-          image: registry.opensource.zalan.do/acid/postgres-operator-ui:v1.3.0
+          image: registry.opensource.zalan.do/acid/postgres-operator-ui:v1.4.0
           ports:
             - containerPort: 8081
               protocol: "TCP"