Re: archive_timeout behavior for no activity

Kevin Grittner wrote:
> Bruce Momjian <bruce@momjian.us> wrote:
>  
> > Looking at the archive_timeout documentation and
> > CheckArchiveTimeout(), it appears we force a new xlog file and
> > archive it even if no activity has been recorded in the xlog file.
> > Is this correct?  Should we document this or fix it so only xlog
> > files with contents are archived?
>  
> Er, you can probably blame me for that.  Tom was going to fix it and
> I pointed out that it would break our monitoring of our warm standby
> processes.  We have a one hour maximum and send alerts if we've gone
> 75 minutes or more without receiving a WAL file from one of our
> databases.  Of course, if we had a nicer way to know that we were
> up-to-date with our WAL file copies, we wouldn't need this; but
> right now there aren't a lot of options for monitoring these things.

I am dismayed that we are using a 16MB file for monitoring archive
activity.  Can't you use pg_current_xlog_location() and only check for
an archive file when that location changes?

Anyway, I have updated the documentation with the attached patch to
mention this issue, and added a C comment as well.

Is there a TODO here?

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +