Re: Configuring synchronous replication

On Wed, Sep 22, 2010 at 12:51 PM, Joshua D. Drake <jd(at)commandprompt(dot)com> wrote:
> On Wed, 2010-09-22 at 17:43 +0100, Thom Brown wrote:
>
>> So...
>>
>> sync_rep_services = {critical: recv=2, fsync=2, replay=1;
>>                      important: fsync=3;
>>                      reporting: recv=2, apply=1}
>>
>> becomes ...
>>
>> sync_rep_services.critical.recv = 2
>> sync_rep_services.critical.fsync = 2
>> sync_rep_services.critical.replay = 2
>> sync_rep_services.important.fsync = 3
>> sync_rep_services.reporting.recv = 2
>> sync_rep_services.reporting.apply = 1
>>
>> I actually started to give this example to demonstrate how cumbersome
>> it would look... but now that I've just typed it out, I've changed my
>> mind.  I actually like it!
>
> With respect, this is ugly. Very ugly. Why do we insist on cryptic
> parameters within a config file which should be set within the database
> by a super user.
>
> I mean really?
>
> ALTER CLUSTER ENABLE [SYNC] REPLICATION ON db.foobar.com PORT 5432 ALIAS
> CRITICAL;
> ALTER CLUSTER SET REPLICATION CRITICAL RECEIVE FOR 2;
> ALTER CLUSTER SET REPLICATION CRITICAL FSYNC FOR 2;
> ALTER CLUSTER SET REPLICATION CRITICAL REPLAY FOR 2;
>
> Or some such thing. I saw Heiiki's reply but really the idea that we are
> shoving this all into the postgresql.conf is cumbersome.

I think it should be a separate config file, and I think it should be
a config file that can be edited using DDL commands as you propose.
But it CAN'T be a system catalog, because, among other problems, that
rules out cascading slaves, which are a feature a lot of people
probably want to eventually have.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise Postgres Company