Horton

Re: [HACKERS] Restricting maximum keep segments by repslots

Peter Eisentraut <peter.eisentraut@2ndquadrant.com>

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From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>, sawada.mshk@gmail.com
Cc: pgsql-hackers@lists.postgresql.org, thomas.munro@enterprisedb.com, sk@zsrv.org, michael.paquier@gmail.com, andres@anarazel.de
Date: 2018-09-06T20:32:21Z
Lists: pgsql-hackers 
This documentation

+       <para>
+        Specify the maximum size of WAL files
+        that <link linkend="streaming-replication-slots">replication
+        slots</link> are allowed to retain in the
<filename>pg_wal</filename>
+        directory at checkpoint time.
+        If <varname>max_slot_wal_keep_size</varname> is zero (the default),
+        replication slots retain unlimited size of WAL files.
+       </para>

doesn't say anything about what happens when the limit is exceeded.
Does the system halt until the WAL is fetched from the slots?  Do the
slots get invalidated?

Also, I don't think 0 is a good value for the default behavior.  0 would
mean that a slot is not allowed to retain any more WAL than already
exists anyway.  Maybe we don't want to support that directly, but it's a
valid configuration.  So maybe use -1 for infinity.

-- 
Peter Eisentraut              http://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