postgres-repmgr

PostgreSQL Docker image with repmgrd for automatic failover

This is heavily based on 2ndQuadrant's blog post on the topic), but:

• several environment variables have been added
• this image doesn't use passwordless replication. Make sure to set REPMGR_PASSWORD
• I've taken the liberty to add my own pg_recall PostgreSQL extension, because I need it on all my production clusters.
  It's a source-only extension, so unless you call CREATE EXTENSION recall, it's entirely inactive.
• a few other minor changes

Environment:

This docker image uses the following environment variables (with their defaults if applicable):

• REPMGR_USER=repmgr
• REPMGR_DB=repmgr
• REPMGR_PASSWORD (required)
  Use something like pwgen -n 24 1 to generate a random one (and make sure you use the same one on all your nodes
• NODE_HOST=
  If set, this is used in the conninfo string (used by other nodes to connect to this one.
  If empty, hostname -f is used Make sure you use a hostname the others can resolve (or an IP address)
• WITNESS= If non-empty, this node is set up as witness node (i.e. won't hold actual data but still has a vote in leader election).