Horton

Re: Improve handling of parameter differences in physical replication

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

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From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: PostgreSQL-development <pgsql-hackers@postgresql.org>
Cc: Sergei Kornilov <sk@zsrv.org>, Masahiko Sawada <masahiko.sawada@2ndquadrant.com>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, Álvaro Herrera <alvherre@2ndquadrant.com>
Date: 2020-06-24T08:00:00Z
Lists: pgsql-hackers

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Here is another stab at this subject.

This is a much simplified variant:  When encountering a parameter change 
in the WAL that is higher than the standby's current setting, we log a 
warning (instead of an error until now) and pause recovery.  If you 
resume (unpause) recovery, the instance shuts down as before.

This allows you to keep your standbys running for a bit (depending on 
lag requirements) and schedule the required restart more deliberately.

I had previously suggested making this new behavior configurable, but 
there didn't seem to be much interest in that, so I have not included 
that there.

The documentation changes are mostly carried over from previous patch 
versions (but adjusted for the actual behavior of the patch).

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Pause recovery for insufficient parameter settings

  2. Replace a macro by a function

  3. Improve handling of parameter differences in physical replication

  4. Prefer standby promotion over recovery pause.