Re: Race between KeepFileRestoredFromArchive() and restartpoint

On 8/4/22 04:06, Kyotaro Horiguchi wrote:
> At Wed, 3 Aug 2022 23:24:56 -0700, Noah Misch <noah(at)leadboat(dot)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

Looks good to me as well.

>>>> 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.

Hmmm, OK. We certainly have a fairly serious issue here, i.e. pg_wal
growing without bound. Even if we are not sure what is causing it, how
confident are we that the patches applied to v15 would fix it?

Regards,
-David