Re: Standalone synchronous master

On 01/09/2014 12:05 AM, Stephen Frost wrote:
> * Andres Freund (andres(at)2ndquadrant(dot)com) wrote:
>> On 2014-01-08 17:56:37 -0500, Stephen Frost wrote:
>>> * Andres Freund (andres(at)2ndquadrant(dot)com) wrote:
>>>> That's why you should configure a second standby as another (candidate)
>>>> synchronous replica, also listed in synchronous_standby_names.
>>> Perhaps we should stress in the docs that this is, in fact, the *only*
>>> reasonable mode in which to run with sync rep on? Where there are
>>> multiple replicas, because otherwise Drake is correct that you'll just
>>> end up having both nodes go offline if the slave fails.
>> Which, as it happens, is actually documented.
> I'm aware, my point was simply that we should state, up-front in
> 25.2.7.3 *and* where we document synchronous_standby_names, that it
> requires at least three servers to be involved to be a workable
> solution.
>
> Perhaps we should even log a warning if only one value is found in
> synchronous_standby_names...
You can have only one name in synchronous_standby_names and
have multiple slaves connecting with that name

Also, I can attest that I have had clients who want exactly that - a system
stop until admin intervention in case of a designated sync standby failing.

And they actually run more than one standby, they just want to make
sure that sync rep to 2nd data center always happens.

Cheers

--
Hannu Krosing
PostgreSQL Consultant
Performance, Scalability and High Availability
2ndQuadrant Nordic OÜ