Horton

Re: Race between KeepFileRestoredFromArchive() and restartpoint

Kyotaro Horiguchi <horikyota.ntt@gmail.com>

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From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: noah@leadboat.com
Cc: david@pgmasters.net, pgsql-hackers@postgresql.org, don@seiler.us
Date: 2022-08-04T08:06:40Z
Lists: pgsql-hackers 
At Wed, 3 Aug 2022 23:24:56 -0700, Noah Misch <noah@leadboat.com> wrote in 
> > > I think in this case a HINT might be sufficient to at least keep people from
> > > wasting time tracking down a problem that has already been fixed.
> 
> Here's a patch to add that HINT.  I figure it's better to do this before next
> week's minor releases.  In the absence of objections, I'll push this around
> 2022-08-05 14:00 UTC.

+1

> > > However, there is another issue [1] that might argue for a back patch if
> > > this patch (as I believe) would fix the issue.
> > 
> > > [1] https://www.postgresql.org/message-id/CAHJZqBDxWfcd53jm0bFttuqpK3jV2YKWx%3D4W7KxNB4zzt%2B%2BqFg%40mail.gmail.com
> > 
> > That makes sense.  Each iteration of the restartpoint recycle loop has a 1/N
> > chance of failing.  Recovery adds >N files between restartpoints.  Hence, the
> > WAL directory grows without bound.  Is that roughly the theory in mind?
> 
> On further reflection, I don't expect it to happen that way.  Each failure
> message is LOG-level, so the remaining recycles still happen.  (The race
> condition can yield an ERROR under PreallocXlogFiles(), but recycling is
> already done at that point.)

I agree to this.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center

Commits

  1. Skip WAL recycling and preallocation during archive recovery.

  2. Don't ERROR on PreallocXlogFiles() race condition.

  3. Remove XLogFileInit() ability to unlink a pre-existing file.

  4. In XLogFileInit(), fix *use_existent postcondition to suit callers.

  5. Remove XLogFileInit() ability to skip ControlFileLock.

  6. Add HINT for restartpoint race with KeepFileRestoredFromArchive().

  7. Complete TODO item: