POSTGRESQL REPLICATION
----------------------
This file contains the procedure for setting up PostgreSQL replication with
a single master and one or more standby servers.
SETUP - ALL SERVERS
-------------------
On each server you must add lines to pg_hba.conf to allow remote replication
connections:
host replication replication 12.34.56.0/24 cert clientcert=1
Replace "12.34.56.0/24" with the standby server IP address (or block).
Every server should have one line for every server in the replication setup,
including itself--thus all servers should have the same lines. This enables
quickly changing which server is the master without extra configuration.
SETTING UP STANDBYS
-------------------
You must run "setup-standby.sh" on each server to turn it into a standby.
Before you run it, open the script in a text editor, and verify
the value of each variable in the Configuration section at the top of the
script.
When you run it, specify the master server as the first argument, e.g.:
$ ./setup-standby.sh dds1-ancf
The existing PostgreSQL data directory on the new standby server will be
destroyed, and it will become a replica of the master. pg_hba.conf will
be retained (i.e., will not be replaced with the copy from master).
Note that a standby can replicate from another standby--it does not have to
replicate directly from the master. This is useful for reducing WAN traffic.
FAILOVER
--------
To promote a standby to master:
1. Stop PostgreSQL on the master if it is running.
2. On the standby, create the file "/awips2/data/promote". The standby will
stop replication and recognize itself as the new master.
3. On the old master and the other standbys, run setup-standby.sh with the
hostname of the new master, to re-initialize them and start replicating
from the new master.
