On 11/16/2016 04:51 PM, Israel Brewster wrote:I've been playing around with streaming replication, and discovered that
the following series of steps *appears* to work without complaint:
- Start with master on server A, slave on server B, replicating via
streaming replication with replication slots.
- Shut down master on A
- Promote slave on B to master
- Create recovery.conf on A pointing to B
- Start (as slave) on A, streaming from B
After those steps, A comes up as a streaming replica of B, and works as
expected. In my testing I can go back and forth between the two servers
all day using the above steps.
My understanding from my initial research, however, is that this
shouldn't be possible - I should need to perform a new basebackup from B
to A after promoting B to master before I can restart A as a slave. Is
the observed behavior then just a "lucky fluke" that I shouldn't rely
You don't say how active the database is, but I going to say it is not active enough for the WAL files on B to go out for scope for A in the time it takes you to do the switch over.
Yeah, not very - this was just in testing, so essentially no activity. So between your response and the one from Jehan-Guillaume de Rorthais, what I'm hearing is that my information about the basebackup being needed was obsoleted with the patch he linked to, and as long as I do a clean shutdown of the master, and don't do too much activity on the *new* master before bringing the old master up as a slave (such that WAL files are lost), then the above failover/failback procedure is perfectly fine to rely on in production - I don't have to worry about there being any hidden gotchas like the new slave not *really* replicating or something.
Thanks! ----------------------------------------------- 5245 Airport Industrial Rd -----------------------------------------------
on? Or is it expected behavior and my understanding about the need for a
new basebackup is simply off? Does the new pg_rewind feature of 9.5
change things? If so, how?
Thanks for your time!
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Israel Brewster
Systems Analyst II
Ravn Alaska
5245 Airport Industrial Rd
Fairbanks, AK 99709
(907) 450-7293
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