Re: Quorum commit for multiple synchronous replication.

On Tue, Nov 15, 2016 at 7:08 PM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> Attached latest version patch incorporated review comments. After more
> thought, I agree and changed the value of standby priority in quorum
> method so that it's not set 1 forcibly. The all standby priorities are
> 1 If s_s_names = 'ANY(*)'.
> Please review this patch.

Sorry for my late reply. Here is my final lookup.

<synopsis>
-<replaceable class="parameter">num_sync</replaceable> ( <replaceable
class="parameter">standby_name</replaceable> [, ...] )
+[ANY] <replaceable class="parameter">num_sync</replaceable> (
<replaceable class="parameter">standby_name</replaceable> [, ...] )
+FIRST <replaceable class="parameter">num_sync</replaceable> (
<replaceable class="parameter">standby_name</replaceable> [, ...] )
<replaceable class="parameter">standby_name</replaceable> [, ...
This can just be replaced with [ ANY | FIRST ]. There is no need for
braces as the keyword is not mandatory.

+ is the name of a standby server.
+ <literal>FIRST</> and <literal>ANY</> specify the method used by
+ the master to control the standby servres.
</para>
s/servres/servers/.

if (priority == 0)
values[7] = CStringGetTextDatum("async");
else if (list_member_int(sync_standbys, i))
- values[7] = CStringGetTextDatum("sync");
+ values[7] = SyncRepConfig->sync_method == SYNC_REP_PRIORITY ?
+ CStringGetTextDatum("sync") : CStringGetTextDatum("quorum");
else
values[7] = CStringGetTextDatum("potential");
This can be simplified a bit as "quorum" is the state value for all
standbys with a non-zero priority when the method is set to
SYNC_REP_QUORUM:
if (priority == 0)
values[7] = CStringGetTextDatum("async");
+ else if (SyncRepConfig->sync_method == SYNC_REP_QUORUM)
+ values[7] = CStringGetTextDatum("quorum");
else if (list_member_int(sync_standbys, i))
values[7] = CStringGetTextDatum("sync");
else

SyncRepConfig data is made external to syncrep.c with this patch as
walsender.c needs to look at the sync method in place, no complain
about that after considering if there could be a more elegant way to
do things without this change.

While reviewing the patch, I have found a couple of incorrectly shaped
sentences, both in the docs and some comments. Attached is a new
version with this word-smithing. The patch is now switched as ready
for committer.
--
Michael