Once a master/slave setup has been created, it usually works flawlessly for a very long time. However, everything can fail, and therefore it is important to understand how a failed server can be replaced with a backup system.
PostgreSQL makes failovers and promotion easy. Basically, all you have to do is use the pg_ctl parameter to tell a replica to promote itself:
pg_ctl -D data_dir promote
The server will disconnect itself from the master and perform the promotion instantly. Remember, the slave might already support thousands of read-only connections while being promoted. One nice feature of PostgreSQL is that all open connections will be turned into read/write connections during promotion—there ...
