Horton

Re: prevent immature WAL streaming

Nathan Bossart <bossartn@amazon.com>

View thread View on postgr.es
From: "Bossart, Nathan" <bossartn@amazon.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>, "alvherre@alvh.no-ip.org" <alvherre@alvh.no-ip.org>
Cc: "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>, "mengjuan.cmj@alibaba-inc.com" <mengjuan.cmj@alibaba-inc.com>, "Jakub.Wartak@tomtom.com" <Jakub.Wartak@tomtom.com>
Date: 2021-08-24T18:28:07Z
Lists: pgsql-hackers 
On 8/23/21, 3:53 PM, "Alvaro Herrera" <alvherre@alvh.no-ip.org> wrote:
> As mentioned in the course of thread [1], we're missing a fix for
> streaming replication to avoid sending records that the primary hasn't
> fully flushed yet.  This patch is a first attempt at fixing that problem
> by retreating the LSN reported as FlushPtr whenever a segment is
> registered, based on the understanding that if no registration exists
> then the LogwrtResult.Flush pointer can be taken at face value; but if a
> registration exists, then we have to stream only till the start LSN of
> that registered entry.

I wonder if we need to move the call to RegisterSegmentBoundary() to
somewhere before WALInsertLockRelease() for this to work as intended.
Right now, boundary registration could take place after the flush
pointer has been advanced, which means GetSafeFlushRecPtr() could
still return an unsafe position.

Nathan

Commits

  1. Fix determination of broken LSN in OVERWRITTEN_CONTRECORD

  2. Fix instability in 026_overwrite_contrecord.pl test.

  3. Fix typo

  4. Change recently added test code for stability

  5. Remove unstable, unnecessary test; fix typo

  6. Repair two portability oversights of new test

  7. Fix WAL replay in presence of an incomplete record

  8. Document XLOG_INCLUDE_XID a little better

  9. Revert "Avoid creating archive status ".ready" files too early"

  10. Avoid creating archive status ".ready" files too early

  11. Fix scenario where streaming standby gets stuck at a continuation record.

  12. Teach xlogreader to follow timeline switches

  13. Forbid using pg_xlogfile_name() and pg_xlogfile_name_offset() during