Re: Standby WAL Cleanup?

2017-08-14 23:08 GMT+02:00 Don Seiler <don(at)seiler(dot)us>:

> On Mon, Aug 14, 2017 at 3:58 PM, Guillaume Lelarge <guillaume(at)lelarge(dot)info
> > wrote:
>
>>
>> The server removes the WAL files it doesn't need anymore, weither it is a
>> primary (after a checkpoint) or a secondary node (after a restartpoint).
>> That's just part of the usual process.
>>
>
> I know the documentation says this about a standalone database regarding
> the "archive_command" parameter.
>
> "It is important that the archive command return zero exit status if and
>> only if it succeeds. Upon getting a zero result, PostgreSQL will assume
>> that the file has been successfully archived, and will remove or recycle
>> it."
>
>
> However on a standby, my understanding is that the archive_command
> parameter is not used. I know for sure that it would fail on the standby
> that I'm looking at.
>
>
Well, then, you need to check your facts :) Since 9.5, a standy can archive
WAL files. See archive_mode and its "new" value : always.

Although I did search for restartpoints and see this now:
>
> In archive recovery or standby mode, the server periodically performs
>> restartpoints which are similar to checkpoints in normal operation: the
>> server forces all its state to disk, updates the pg_control file to
>> indicate that the already-processed WAL data need not be scanned again, and *then
>> recycles any old log segment files in pg_xlog directory*.
>
>
> So I guess that's all the info I need then. Is there any to control that
> behavior if (for reasons I can't think of right now other than cascading
> standby) I wanted to delay that file recycling? Just curious.
>
>
I guess checkpoint_timeout is what you're looking for.

--
Guillaume.