Horton

Re: [HACKERS] Restricting maximum keep segments by repslots

Alvaro Herrera <alvherre@2ndquadrant.com>

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From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: jgdr@dalibo.com, andres@anarazel.de, michael@paquier.xyz, sawada.mshk@gmail.com, peter.eisentraut@2ndquadrant.com, pgsql-hackers@lists.postgresql.org, thomas.munro@enterprisedb.com, sk@zsrv.org, michael.paquier@gmail.com
Date: 2020-04-27T23:40:07Z
Lists: pgsql-hackers

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On 2020-Apr-08, Kyotaro Horiguchi wrote:

> I understand how it happens.
> 
> The latch triggered by checkpoint request by CHECKPOINT command has
> been absorbed by ConditionVariableSleep() in
> InvalidateObsoleteReplicationSlots.  The attached allows checkpointer
> use MyLatch for other than checkpoint request while a checkpoint is
> running.

Hmm, that explanation makes sense, but I couldn't reproduce it with the
steps you provided.  Perhaps I'm missing something.

Anyway I think this patch should fix it also -- instead of adding a new
flag, we just rely on the existing flags (since do_checkpoint must have
been set correctly from the flags earlier in that block.)

I think it'd be worth to verify this bugfix in a new test.  Would you
have time to produce that?  I could try in a couple of days ...

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Save slot's restart_lsn when invalidated due to size

  2. Fix checkpoint signalling

  3. Check slot->restart_lsn validity in a few more places

  4. Allow users to limit storage reserved by replication slots

  5. Remove header noise from test_decoding test

  6. Rework WAL-reading supporting structs

  7. Flip argument order in XLogSegNoOffsetToRecPtr