Fully speced global sidecars (#890)

* implement fully speced global sidecars

* fix issue #924

docs/administrator.md

@@ -507,6 +507,33 @@ A secret can be pre-provisioned in different ways:
 * Automatically provisioned via a custom K8s controller like
   [kube-aws-iam-controller](https://github.com/mikkeloscar/kube-aws-iam-controller)
 
+## Sidecars for Postgres clusters
+
+A list of sidecars is added to each cluster created by the
+operator. The default is empty list.
+
+
+```yaml
+kind: OperatorConfiguration
+configuration:
+  sidecars:
+  - image: image:123
+    name: global-sidecar
+    ports:
+    - containerPort: 80
+    volumeMounts:
+    - mountPath: /custom-pgdata-mountpoint
+      name: pgdata
+  - ...
+```
+
+In addition to any environment variables you specify, the following environment variables are always passed to sidecars:
+
+  - `POD_NAME` - field reference to `metadata.name`
+  - `POD_NAMESPACE` - field reference to `metadata.namespace`
+  - `POSTGRES_USER` - the superuser that can be used to connect to the database
+  - `POSTGRES_PASSWORD` - the password for the superuser
+
 ## Setting up the Postgres Operator UI
 
 Since the v1.2 release the Postgres Operator is shipped with a browser-based

docs/reference/operator_parameters.md

@@ -93,9 +93,17 @@ Those are top-level keys, containing both leaf keys and groups.
   repository](https://github.com/zalando/spilo).
 
 * **sidecar_docker_images**
-  a map of sidecar names to Docker images to run with Spilo. In case of the name
-  conflict with the definition in the cluster manifest the cluster-specific one
-  is preferred.
+  *deprecated*: use **sidecars** instead. A map of sidecar names to Docker images to 
+  run with Spilo. In case of the name conflict with the definition in the cluster 
+  manifest the cluster-specific one is preferred.
+
+* **sidecars**
+  a list of sidecars to run with Spilo, for any cluster (i.e. globally defined sidecars). 
+  Each item in the list is of type 
+  [Container](https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.18/#container-v1-core).
+  Globally defined sidecars can be overwritten by specifying a sidecar in the custom resource with 
+  the same name. Note: This field is not part of the schema validation. If the container specification 
+  is invalid, then the operator fails to create the statefulset.
 
 * **enable_shm_volume**
   Instruct operator to start any new database pod without limitations on shm
@@ -133,8 +141,9 @@ Those are top-level keys, containing both leaf keys and groups.
   at the cost of overprovisioning memory and potential scheduling problems for
   containers with high memory limits due to the lack of memory on Kubernetes
   cluster nodes. This affects all containers created by the operator (Postgres,
-  Scalyr sidecar, and other sidecars); to set resources for the operator's own
-  container, change the [operator deployment manually](../../manifests/postgres-operator.yaml#L20).
+  Scalyr sidecar, and other sidecars except **sidecars** defined in the operator 
+  configuration); to set resources for the operator's own container, change the 
+  [operator deployment manually](../../manifests/postgres-operator.yaml#L20).
   The default is `false`.
 
 ## Postgres users
@@ -206,12 +215,12 @@ configuration they are grouped under the `kubernetes` key.
   Default is true.
 
 * **enable_init_containers**
-  global option to allow for creating init containers to run actions before
-  Spilo is started. Default is true.
+  global option to allow for creating init containers in the cluster manifest to 
+  run actions before Spilo is started. Default is true.
 
 * **enable_sidecars**
-  global option to allow for creating sidecar containers to run alongside Spilo
-  on the same pod. Default is true.
+  global option to allow for creating sidecar containers in the cluster manifest 
+  to run alongside Spilo on the same pod. Globally defined sidecars are always enabled. Default is true.
 
 * **secret_name_template**
   a template for the name of the database user secrets generated by the

docs/user.md

@@ -442,6 +442,8 @@ The PostgreSQL volume is shared with sidecars and is mounted at
 specified but globally disabled in the configuration. The `enable_sidecars`
 option must be set to `true`.
 
+If you want to add a sidecar to every cluster managed by the operator, you can specify it in the [operator configuration](administrator.md#sidecars-for-postgres-clusters) instead.
+
 ## InitContainers Support
 
 Each cluster can specify arbitrary init containers to run. These containers can