| From: | "Bossart, Nathan" <bossartn(at)amazon(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | "alvherre(at)alvh(dot)no-ip(dot)org" <alvherre(at)alvh(dot)no-ip(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, "x4mmm(at)yandex-team(dot)ru" <x4mmm(at)yandex-team(dot)ru>, "a(dot)lubennikova(at)postgrespro(dot)ru" <a(dot)lubennikova(at)postgrespro(dot)ru>, "hlinnaka(at)iki(dot)fi" <hlinnaka(at)iki(dot)fi>, "matsumura(dot)ryo(at)fujitsu(dot)com" <matsumura(dot)ryo(at)fujitsu(dot)com>, "masao(dot)fujii(at)gmail(dot)com" <masao(dot)fujii(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: archive status ".ready" files may be created too early |
| Date: | 2021-08-31 23:31:15 |
| Message-ID: | 83EB9B6A-A6B6-40AB-8B70-0F536CB54BDA@amazon.com |
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| Lists: | pgsql-hackers |
On 8/31/21, 1:30 PM, "Andres Freund" <andres(at)anarazel(dot)de> wrote:
> On 2021-08-31 18:09:36 +0000, Bossart, Nathan wrote:
>> What appears to happen in this case is that bgwriter eventually creates a
>> xl_running_xacts record and nudges walwriter to flush it to disk, at which
>> point the .ready file(s) will be created. That's admittedly a bit fragile.
>
> That's not guaranteed to happen. If e.g. the partial record is a checkpoint or
> a xl_running_xacts, we'll not trigger further WAL writes in the background,
> unless autovacuum ends up doing something.
Right. Per the attached patch, a simple way to handle that could be
to teach XLogBackgroundFlush() to flush to the "earliest" segment
boundary if it doesn't find anything else to do. I think you could
still miss creating a .ready file for the previous segment in single-
user mode, though.
Nathan
| Attachment | Content-Type | Size |
|---|---|---|
| flush-to-boundary.patch | application/octet-stream | 1.3 KB |
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