Re: Quorum commit for multiple synchronous replication.

On Sat, Nov 26, 2016 at 10:27 PM, Michael Paquier
<michael.paquier@gmail.com> wrote:
> On Tue, Nov 15, 2016 at 7:08 PM, Masahiko Sawada <sawada.mshk@gmail.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.

Thank you for reviewing!

>  <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.

Agreed.

> 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.

Thanks. I found a typo in v7 patch, so attached latest v8 patch.

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center