k8s-postgresql

This role will run a postgresql server on a given node and mounts a volume from the host for data persistency purposes. A defined number of slaves servers can be installed (streaming replication). These slave servers will automatically synchronise with the master on startup.

This role requires another one named k8s-common

Main variables

There are two mandatory variables postgres_password ('postgres' user password) and postgres_nodeName (node where the master server will run)

postgres_password : 'postgres'
postgres_nodeName: "node2"

If a slave server is configured you'll need the following vars too:

replication:
  user: <replication_username>
  password: <replication_password>
  master_host: postgres # kubernetes service name of the master server

Then where the slave servers will run

postgres_slave_shards:
  - name: 1
    nodeName: node3
  - name: 2
    nodeName: node4

Postgres configuration

The postgres configuration is controlled by a dictionnary which looks as follows:

postgres_config:
  default_statistics_target : "100"
  maintenance_work_mem : "64MB"
  checkpoint_completion_target : "0.5"
  effective_cache_size : "1GB" # Must be lower than container limits
  work_mem : "4MB"
  wal_buffers : "-1"
  checkpoint_segments : "3"
  shared_buffers : "128MB"
  wal_level: "hot_standby"
  max_wal_senders: "5"
  wal_keep_segments: "32"
  archive_mode: "on"

A similar var named postgres_slave_config can be configured in a clustered architecture.

Replication

The replication is done by using a specific docker image : quay.io/smana/k8s-postgres The entrypoint takes either the argument "postgres" (master server) or "replication" (slaves).

WAL archive

You should consider using a shared storage when you're using a master/slave cluster. This option is possible by using a kubernetes persistent storage. The claim has to be created before running this playbook