Horton

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

Simon Riggs <simon@2ndquadrant.com>

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From: Simon Riggs <simon@2ndQuadrant.com>
To: Florian Pflug <fgp@phlo.org>
Cc: Daniel Farina <daniel@heroku.com>, Chris Redekop <chris@replicon.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2011-10-25T12:51:51Z
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

On Tue, Oct 25, 2011 at 12:39 PM, Florian Pflug <fgp@phlo.org> wrote:

> What I don't understand is how this affects the CLOG. How does oldestActiveXID
> factor into CLOG initialization?

It is an entirely different error.

Chris' clog error was caused by a file read error. The file was
opened, we did a seek within the file and then the call to read()
failed to return a complete page from the file.

The xid shown is 22811359, which is the nextxid in the control file.

So StartupClog() must have failed trying to read the clog page from disk.

That isn't a Hot Standby problem, a recovery problem nor is it certain
its a PostgreSQL problem.

OTOH SlruPhysicalReadPage() does cope gracefully with missing clog
files during recovery, so maybe we can think of a way to make recovery
cope with a SLRU_READ_FAILED error gracefully also. Any ideas?

-- 
 Simon Riggs                   http://www.2ndQuadrant.com/
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