Re: Infinite loop in XLogPageRead() on standby

Alexander Kukushkin <cyberdemn@gmail.com>

From: Alexander Kukushkin <cyberdemn@gmail.com>

To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>

Cc: michael@paquier.xyz, pgsql-hackers@postgresql.org, thomas.munro@gmail.com

Date: 2024-03-06T10:34:29Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Fix header check for continuation records where standbys could be stuck
- 0f0431e919f4 13.19 landed
- a2d4f806c4b9 14.16 landed
- 26554faccc97 15.11 landed
- 2c2e1d4f42c0 16.7 landed
- e6767c0ed16f 17.3 landed
- 6cf1647d87e7 18.0 landed
Move routines to manipulate WAL into PostgreSQL::Test::Cluster
- c9e50ce2a044 13.19 landed
- 50406b15540c 14.16 landed
- e5d113057d5f 15.11 landed
- 9420f9bb61e6 16.7 landed
- 149ed87e22ce 17.3 landed
- 32a18cc0a73d 18.0 landed
Prevent archive recovery from scanning non-existent WAL files.
- 4bd0ad9e44be 13.0 cited
Fix scenario where streaming standby gets stuck at a continuation record.
- 066871980183 11.0 cited

Hi Kyotaro,

Oh, now I understand what you mean. Is the retry supposed to happen only
when we are reading the very first page from the WAL file?

On Wed, 6 Mar 2024 at 09:57, Kyotaro Horiguchi <horikyota.ntt@gmail.com>
wrote:

>
> xlogrecovery.c:
> @@ -3460,8 +3490,10 @@ retry:
>          * responsible for the validation.
>          */
>         if (StandbyMode &&
> +               targetPagePtr % 0x100000 == 0 &&
>                 !XLogReaderValidatePageHeader(xlogreader, targetPagePtr,
> readBuf))
>         {
>
>
Hmm, I think you meant to use wal_segment_size, because 0x100000 is just
1MB. As a result, currently it works for you by accident.


> Thus, I managed to reproduce precisely the same situation as you
> described utilizing your script with modifications and some core
> tweaks, and with the change above, I saw that the behavior was
> fixed. However, for reasons unclear to me, it shows another issue, and
> I am running out of time and need more caffeine. I'll continue
> investigating this tomorrow.
>

Thank you for spending your time on it!

-- 
Regards,
--
Alexander Kukushkin