merge with master and revert spec naming in k8sres

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)
+}