The problem with maintaining a separate archive is that one need to write some additional scripts to periodically remove older log files from the archive and that gets complicated with a setup having one master and multiple slaves.
I think it is a better idea to club compression and clean up in the core itself, may at a later release. A better approach to cleanup is that the walsender process decides when to cleanup a particular logfile based on the feedback from the all the registered slaves. If a slave is not reachable or falls behind for too long, then that slave should be banned from the setup (log the event in pg_replication.log ???). The replication status for each slave can be maintained in something like pg_slave_replica_status catalog table.
When it comes to compression, walsender can compress the each chunk of data that it streams (increasing the streaming_delay may improve compression ratio, hence a balance has to be struck between compression and sustainable-data-loss-in-case-of-failure)
Although I could visualise this design would be much better than leaving it to external utilities, I'm not that good at C language and hence only proposing a design and not a patch. I hope my suggestion will be received in good spirit.
Thanks and Regards,
Samba
PS:
I have wrongly stated that master server had to be restarted in case of long disconnects, sorry that was not true. But I still feel that requiring restart of standby server to resume replication should be avoided, if possible.
And, I strongly feel that a breakage in replication must be logged by both master server and the concerned slave servers.
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On Wed, Aug 24, 2011 at 11:03 PM, Alan Hodgson
<ahodgson@simkin.ca> wrote:
On August 24, 2011 08:33:17 AM Samba wrote:
> One strange thing I noticed is that the pg_xlogs on the master have
> outsized the actual data stored in the database by at least 3-4 times,
> which was quite surprising. I'm not sure if 'restore_command' has anything
> to do with it. I did not understand why transaction logs would need to be
> so many times larger than the actual size of the database, have I done
> something wrong somewhere?
If you archive them instead of keeping them in pg_xlog, you can gzip them.
They compress reasonably well.
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