On 2014-05-05 10:30:17 -0700, Josh Berkus wrote: > On 05/05/2014 10:25 AM, Andres Freund wrote: > > On 2014-05-05 10:16:27 -0700, Josh Berkus wrote: > >> On 05/03/2014 01:07 AM, Andres Freund wrote: > >>> On 2014-05-02 18:57:08 -0700, Josh Berkus wrote: > >>>> Just got a report of a replication issue with 9.2.8 from a community > >>>> member: > >>>> > >>>> Here's the sequence: > >>>> > >>>> 1) A --> B (sync rep) > >>>> > >>>> 2) Shut down B > >>>> > >>>> 3) Shut down A > >>>> > >>>> 4) Start up B as a master > >>>> > >>>> 5) Start up A as sync replica of B > >>>> > >>>> 6) A successfully joins B as a sync replica, even though its transaction > >>>> log is 1016 bytes *ahead* of B. > >>>> > >>>> 7) Transactions written to B all hang > >>>> > >>>> 8) Xlog on A is now corrupt, although the database itself is OK > >>> > >>> This is fundamentally borked practice. > >>> > >>>> Now, the above sequence happened because of the user misunderstanding > >>>> what sync rep really means. However, A should not have been able to > >>>> connect with B in replication mode, especially in sync rep mode; that > >>>> should have failed. Any thoughts on why it didn't? > >>> > >>> I'd guess that B, while starting up, has written further WAL records > >>> bringing it further ahead of A. > >> > >> Apparently not; from what I've seen pg_stat_replication even *shows* > >> that the replica is ahead of the master.
That's the shutdown record from A that I've talked about. > Futher, Postgres should have > >> recognized that there was a timeline branch point before A's last > >> record, no? > > > > There wasn't any timeline increase because - as far as I understand the > > above - there wasn't any promotion. The cluster was shut down and > > recovery.conf was created/removed respectively. > > Ah, oops, left out a step. B was promoted. Still a user error. You need to reclone. Depending on how archiving and the target timeline was configured the timeline increase won't be treated as an error... Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
