Re: Support for N synchronous standby servers

On Tue, Sep 16, 2014 at 5:25 AM, Robert Haas <robertmhaas@gmail.com> wrote:
> On Mon, Sep 15, 2014 at 3:00 PM, Michael Paquier
> <michael.paquier@gmail.com> wrote:
>> At least a set of hooks has the merit to say: do what you like with
>> your synchronous node policy.
>
> Sure.  I dunno if people will find that terribly user-friendly, so we
> might not want that to be the ONLY thing we offer.
Well, user-friendly interface is actually the reason why a simple GUC
integer was used in the first series of patches present on this thread
to set as sync the N-nodes with the lowest priority. I could not come
up with something more simple. Hence what about doing the following:
- A patch refactoring code for pg_stat_get_wal_senders and
SyncRepReleaseWaiters as there is in either case duplicated code in
this area to select the synchronous node as the one connected with
lowest priority
- A patch defining the hooks necessary, I suspect that two of them are
necessary as mentioned upthread.
- A patch for a contrib module implementing an example of simple
policy. It can be a fancy thing with a custom language or even a more
simple thing.
Thoughts? Patch 1 refactoring the code is a win in all cases.
Regards,
-- 
Michael