Re: is sync rep stalled?

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
> I think the point here is that it's possible to have sync-rep
> configurations in which it's impossible to take a base backup.

Sorry to be slow. I still don't understand that problem.

I can understand why people want "wait forever", but I can't understand
when the following strange idea apply: consider my non-ready standby
there as a full member of the distributed setup already.

I've been making plenty of noise about this topic in the past, at the
beginning of plans for SR in 9.0 IIRC, pushing Heikki into having a
worked out state machine to figure out what are the known states of a
standby and what we can do with each. We've cancelled that and said it
would maybe necessary for Synchronous Replication. Here we go, right?

So, first thing first, when is it a good idea to consider a standby
that's not yet had its base backup, let alone validated that after
taking it the master still has enough WAL for the backup to be valid as
far as initialising the slave goes, to consider this broken standby as
someone we wait forever on?

I say a standby is registered when it's currently "attached" and already
able to keep up in async. That's a time when you can slow down the
master until this new member catches up to full sync or whatever you've
setup.

Regards,
--
Dimitri Fontaine
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support

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