Horton

Re: Hot Backup with rsync fails at pg_clog if under load

Chris Redekop <chris@replicon.com>

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From: Chris Redekop <chris@replicon.com>
To: Simon Riggs <simon@2ndquadrant.com>
Cc: Florian Pflug <fgp@phlo.org>, Daniel Farina <daniel@heroku.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2011-10-26T15:36:56Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Derive oldestActiveXid at correct time for Hot Standby.

  2. Start Hot Standby faster when initial snapshot is incomplete.

  3. Fix timing of Startup CLOG and MultiXact during Hot Standby

> And I think they also reported that if they didn't run hot standby,
> but just normal recovery into a new master, it didn't have the problem
> either, i.e. without hotstandby, recovery ran, properly extended the
> clog, and then ran as a new master fine.

Yes this is correct...attempting to start as hotstandby will produce the
pg_clog error repeatedly and then without changing anything else, just
turning hot standby off it will start up successfully.

> This fits the OP's observation ob the
> problem vanishing when pg_start_backup() does an immediate checkpoint.

Note that this is *not* the behaviour I'm seeing....it's possible it happens
more frequently without the immediate checkpoint, but I am seeing it happen
even with the immediate checkpoint.

> This is a different problem and has already been reported by one of
> your colleagues in a separate thread, and answered in detail by me
> there. There is no bug related to this error message.

Excellent...I will continue this discussion in that thread.