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Avoid creating archive status ".ready" files too early

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WAL records may span multiple segments, but XLogWrite() does not
wait for the entire record to be written out to disk before
creating archive status files.  Instead, as soon as the last WAL page of
the segment is written, the archive status file is created, and the
archiver may process it.  If PostgreSQL crashes before it is able to
write and flush the rest of the record (in the next WAL segment), the
wrong version of the first segment file lingers in the archive, which
causes operations such as point-in-time restores to fail.

To fix this, keep track of records that span across segments and ensure
that segments are only marked ready-for-archival once such records have
been completely written to disk.

This has always been wrong, so backpatch all the way back.

Author: Nathan Bossart <bossartn@amazon.com>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reviewed-by: Ryo Matsumura <matsumura.ryo@fujitsu.com>
Reviewed-by: Andrey Borodin <x4mmm@yandex-team.ru>
Discussion: https://postgr.es/m/CBDDFA01-6E40-46BB-9F98-9340F4379505@amazon.com
This commit is contained in:
Alvaro Herrera
2021-08-23 15:50:35 -04:00
parent f7bda63a48
commit 515e3d84a0
8 changed files with 234 additions and 24 deletions
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src/include/access/xlog.h
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@ -315,6 +315,7 @@ extern XLogRecPtr GetInsertRecPtr(void);
extern XLogRecPtr GetFlushRecPtr(void);
extern XLogRecPtr GetLastImportantRecPtr(void);
extern void RemovePromoteSignalFiles(void);
extern void NotifySegmentsReadyForArchive(XLogRecPtr flushRecPtr);
extern bool PromoteIsTriggered(void);
extern bool CheckPromoteSignal(void);