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

Simon Riggs <simon@2ndquadrant.com>

From: Simon Riggs <simon@2ndQuadrant.com>

To: Daniel Farina <daniel@heroku.com>

Cc: Chris Redekop <chris@replicon.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>

Date: 2011-10-23T23:33:59Z

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 →

Derive oldestActiveXid at correct time for Hot Standby.
- 656bba95af39 9.0.6 cited
Start Hot Standby faster when initial snapshot is incomplete.
- ff8451aa14c8 9.0.6 cited
Fix timing of Startup CLOG and MultiXact during Hot Standby
- 2f55c535e1f0 9.0.6 cited

On Sun, Oct 23, 2011 at 9:48 PM, Daniel Farina <daniel@heroku.com> wrote:

> Having digged at this a little -- but not too much -- the problem
> seems to be that postgres is reading the commit logs way, way too
> early, that is to say, before it has played enough WAL to be
> 'consistent' (the WAL between pg_start and pg_stop backup).  I have
> not been able to reproduce this problem (I think) after the message
> from postgres suggesting it has reached a consistent state; at that
> time I am able to go into hot-standby mode.

The WAL appears too early because the other control info is later than
it should be.

So this is approx backwards and nothing related to consistent state,
but thanks for drawing my attention to this.

-- 
 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services