Hi Team,
Let us say we have a Master (M1) and a Slave (S1) in replication using Streaming Replication.
I stopped all my writes from Application and i switched a WAL and made sure it is replicated to Slave.
I have then shutdown M1. And ran a promote on S1.
Now S1 is my new Master with a new timeline.
Now, in order to let M1 replicate changes from S1 (Master) as a Slave, i am able to succeed with the following approach.
Add recovery_target_timeline = 'latest' and then have the appropriate entries such as primary_conninfo, standby_mode in the recovery.conf and start the M1 using pg_ctl.
I see that it M1 (Old Master) is able to catch up with S1 (New Master). And replication is going fine.
Have you ever faced or think of a problem with this approach ?
Points to note are :
1. Master was neatly SHUTDOWN after shutting down writes. So, it has not diverged. (If it is diverged, i would of course need a pg_rewind like approach).
2. It was a planned switchover. During this entire process, there are no writes to M1 (before Switchover) or S1 (after promote).
3. timeline history file is also accessible to the Old Master (M1) after S1 was promoted. No transactions, so no WALs generated, may be 1 or 2 considering timeout, etc.
It looks like a clean approach, but do you think there could be a problem with this approach of rebuilding Old Master as a Slave ? Is this approach still okay ?
Thanks,
Avinash Vallarapu.