On Tuesday, September 25, 2012 12:39 PM Heikki Linnakangas wrote: > On 24.09.2012 16:33, Amit Kapila wrote: > > On Tuesday, September 11, 2012 10:53 PM Heikki Linnakangas wrote: > >> I've been working on the often-requested feature to handle timeline > >> changes over streaming replication. At the moment, if you kill the > >> master and promote a standby server, and you have another standby > >> server that you'd like to keep following the new master server, you > >> need a WAL archive in addition to streaming replication to make it > >> cross the timeline change. Streaming replication will just error > out. > >> Having a WAL archive is usually a good idea in complex replication > >> scenarios anyway, but it would be good to not require it. > > > > Confirm my understanding of this feature: > > > > This feature is for case when standby-1 who is going to be promoted > to > > master has archive mode 'on'. > > No. This is for the case where there is no WAL archive. > archive_mode='off' on all servers. > > Or to be precise, you can also have a WAL archive, but this patch > doesn't affect that in any way. This is strictly about streaming > replication. > > > As in that case only its timeline will change. > > The timeline changes whenever you promote a standby. It's not related > to > whether you have a WAL archive or not.
Yes that is correct. I thought timeline change happens only when somebody does PITR. Can you please tell me why we change timeline after promotion, because the original Timeline concept was for PITR and I am not able to trace from code the reason why on promotion it is required? > > > If above is right, then there can be other similar scenario's where > it can > > be used: > > > > Scenario-1 (1 Master, 1 Stand-by) > > 1. Master (archive_mode=on) goes down. > > 2. Master again comes up > > 3. Stand-by tries to follow it > > > > Now in above scenario also due to timeline mismatch it gives error, > but your > > patch should fix it. > > If the master simply crashes or is shut down, and then restarted, the > timeline doesn't change. The standby will reconnect / poll the archive, > and sync up just fine, even without this patch. How about when Master does PITR when it comes again? With Regards, Amit Kapila. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
