Re: pg_receivewal documentation

On Tue, Jul 16, 2019 at 01:03:12PM -0400, Jesper Pedersen wrote:
> Here is the patch for that.

+ <para>
+ Note that while WAL will be flushed with this setting,
+ <application>pg_receivewal</application> never applies it, so
+ <xref linkend="guc-synchronous-commit"/> must not be set to
+ <literal>remote_apply</literal> if <application>pg_receivewal</application>
+ is the only synchronous standby. Similarly, if
+ <application>pg_receivewal</application> is part of a quorum-based
+ set of synchronous standbys, it won't count towards the quorum if
+ <xref linkend="guc-synchronous-commit"/> is set to
+ <literal>remote_apply</literal>.
+ </para>

I think we should really document the caveat with priority-based sets
of standbys as much as quorum-based sets. For example if a user sets
synchronous_commit = remote_apply in postgresql.conf, and then sets
s_s_names to '2(pg_receivewal, my_connected_standby)' to get a
priority-based set, then you have the same problem, and pg_receivewal
is not the only synchronous standby in this configuration. The patch
does not cover that case properly.
--
Michael