Horton

Re: [BUG] non archived WAL removed during production crash recovery

Jehan-Guillaume de Rorthais <jgdr@dalibo.com>

View thread View on postgr.es
From: Jehan-Guillaume de Rorthais <jgdr@dalibo.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>, masao.fujii@oss.nttdata.com, pgsql-bugs@lists.postgresql.org
Date: 2020-04-20T12:22:35Z
Lists: pgsql-bugs, pgsql-hackers 
On Mon, 20 Apr 2020 16:34:44 +0900
Michael Paquier <michael@paquier.xyz> wrote:
[...]
> > By the way I noticed that RecoveryState is exactly a subset of
> > DBState.  And changes of SharedRecoveryState happens side-by-side with
> > ControlFileData->state in most places.  Coundn't we just usee
> > ControlFile->state instead of SharedRecoveryState?
> 
> I actually found confusing to use the same thing, because then the
> reader would thing that SharedRecoveryState could be set to more
> values but we don't want that.

I thought about this while studying various possible fix. 

https://www.postgresql.org/message-id/flat/20200401181735.11100908%40firost#6192afba4e4549b8d9bac03168bad46b

The problem is that we would have to read the controldata file each time we
wonder if a segment should be archived/removed. Moreover, the controldata
file might not be in sync quickly enough with the real state for some other
code path or futur needs.

[...]
> Attached is an updated patch, where I tweaked more comments.
> 
> Jehan-Guillaume, who is your colleague who found originally about this
> problem?  We should credit him in the commit message.

Indeed, Benoît Lobréau reported this behavior to me.

Regards,

Commits

  1. Fix interpolation in test name.

  2. Add more TAP coverage for archive status with crash recovery of standbys

  3. Fix handling of WAL segments ready to be archived during crash recovery

  4. Fix WAL recycling on standbys depending on archive_mode