On Nov 18, 2016, at 5:48 AM, Jehan-Guillaume de Rorthais <iog...@free.fr> wrote: > > On Thu, 17 Nov 2016 08:26:59 -0900 > Israel Brewster <isr...@ravnalaska.net <mailto:isr...@ravnalaska.net>> wrote: > >>> On Nov 16, 2016, at 4:24 PM, Adrian Klaver <adrian.kla...@aklaver.com> >>> wrote: >>> >>> 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) > > Just set up wal archiving to avoid this (and have PITR backup as a side > effect).
Good point. Streaming replication may not *need* WAL archiving to work, but having it can provide other benefits than just replication. I'll have to look more into the PITR backup though - that's something that sounds great to have, but I have no clue, beyond the concept, how it works. :-) ----------------------------------------------- Israel Brewster Systems Analyst II Ravn Alaska 5245 Airport Industrial Rd Fairbanks, AK 99709 (907) 450-7293 ----------------------------------------------- > > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org > <mailto:pgsql-general@postgresql.org>) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general > <http://www.postgresql.org/mailpref/pgsql-general>
