Add logical backup (#442)

* Add k8s cron job to spawn logical backups

* Minor doc updates

docs/reference/cluster_manifest.md

@@ -14,6 +14,8 @@ measurements. Please, refer to the [Kubernetes
 documentation](https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/)
 for the possible values of those.
 
+:exclamation: If both operator configmap/CRD and a Postgres cluster manifest define the same parameter, the value from the Postgres cluster manifest is applied.
+
 ## Manifest structure
 
 A postgres manifest is a `YAML` document. On the top level both individual
@@ -45,7 +47,7 @@ Those parameters are grouped under the `metadata` top-level key.
 
 ## Top-level parameters
 
-Those are parameters grouped directly under  the `spec` key in the manifest.
+These parameters are grouped directly under  the `spec` key in the manifest.
 
 * **teamId**
   name of the team the cluster belongs to. Changing it after the cluster
@@ -117,6 +119,12 @@ Those are parameters 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).
 
+* **enableLogicalBackup**
+  Determines if the logical backup of this cluster should be taken and uploaded to S3. Default: false.
+
+* **logicalBackupSchedule**
+  Schedule for the logical backup k8s cron job. Please take [the reference schedule format](https://kubernetes.io/docs/tasks/job/automated-tasks-with-cron-jobs/#schedule) into account. Default: "30 00 \* \* \*"
+
 ## Postgres parameters
 
 Those parameters are grouped under the `postgresql` top-level key.

docs/reference/operator_parameters.md

@@ -51,6 +51,8 @@ parameters, those parameters have no effect and are replaced by the
 `CRD_READY_WAIT_INTERVAL` and `CRD_READY_WAIT_TIMEOUT` environment variables.
 They will be deprecated and removed in the future.
 
+For the configmap operator configuration, the [default parameter values](https://github.com/zalando-incubator/postgres-operator/blob/master/pkg/util/config/config.go#L14) mentioned here are likely to be overwritten in your local operator installation via your local version of the operator configmap. In the case you use the operator CRD, all the CRD defaults are provided in the [operator's default configuration manifest](https://github.com/zalando-incubator/postgres-operator/blob/master/manifests/postgresql-operator-default-configuration.yaml)
+
 Variable names are underscore-separated words.
 
 
@@ -476,4 +478,16 @@ scalyr sidecar. In the CRD-based configuration they are grouped under the
   Memory limit value for the Scalyr sidecar. The default is `1Gi`.
 
 
-For the configmap operator configuration, the [default parameter values](https://github.com/zalando/postgres-operator/blob/master/pkg/util/config/config.go#L14) mentioned here are likely to be overwritten in your local operator installation via your local version of the operator configmap. In the case you use the operator CRD, all the CRD defaults are provided in the [operator's default configuration manifest](https://github.com/zalando/postgres-operator/blob/master/manifests/postgresql-operator-default-configuration.yaml)
+## Logical backup
+
+  These parameters configure a k8s cron job managed by the operator to produce Postgres logical backups.
+  In the CRD-based configuration those parameters are grouped under the `logical_backup` key.
+
+  * **logical_backup_schedule**
+    Backup schedule in the cron format. Please take [the reference schedule format](https://kubernetes.io/docs/tasks/job/automated-tasks-with-cron-jobs/#schedule) into account. Default: "30 00 \* \* \*"
+  
+  * **logical_backup_docker_image**
+    Docker image for the pods of the cron job. Must implement backup logic and correctly handle pod and job restarts. The default image runs `pg_dumpall` (on a replica if possible) and uploads compressed results to an S3 bucket under the key `/spilo/pg_cluster_name/cluster_k8s_uuid/logical_backups` Default: "registry.opensource.zalan.do/acid/logical-backup" 
+
+  * **logical_backup_s3_bucket**
+    S3 bucket to store backup results. The bucket has to be present and accessible by Postgres pods. Default: empty.