Re: status/timeline of pglogical?

El 12/05/16 a las 12:26, Magnus Hagander escribió:
>
> On May 12, 2016 16:57, "Bruce Momjian" <bruce(at)momjian(dot)us
> <mailto:bruce(at)momjian(dot)us>> wrote:
>>
>> On Thu, May 12, 2016 at 10:37:28AM -0400, Robert Haas wrote:
>> > 3. I think we need to replace pg_upgrade with a real in-place upgrade
>> > scheme so that you just fire up the new version of the server on your
>> > old data directory, and it rejiggers things in place without needing
>> > to create a new cluster and migrate stuff over to it. I think that
>> > actually making this work is a huge engineering effort, and I have no
>> > plans to undertake it in the near term, but I think it has to be done.
>> > pg_upgrade isn't reliable enough, and using pglogical means you need a
>> > second machine. Maybe everybody should run with a standby, but not
>> > everyone does.
>>
>> I don't see why you can't have the pg_logical slave be on the same
>> server as the master for an upgrade. It will double the write volume
>> while it is active, but assuming it is setup only to perform a major
>> version upgrade, it should be fine.
>>
>
> I think that's a pretty bad assumption. A lot, if not most, of the
> people who actually need zero downtime upgrades don't have 50% extra
> space and in particular not 50% extra performance on their servers to
> throw at that.

I have the feeling that people who actually *need* zero downtime, have
at least 1 standbys they can use to perform the online upgrade.

> Can it be made to work? Sure. But I definitely agree with Robert that we
> need "real" in place upgrades at some point.

It would be a neat feature. The question is if there will be such a
solution and if it will be or not reliable.

Saludos,

--
Martín Marqués http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services