Re: is sync rep stalled?

On 09/30/2010 04:54 PM, Yeb Havinga wrote:
> Heikki Linnakangas wrote:
>> You do realize that to be able to guarantee zero data loss, the master
>> will have to stop committing new transactions if the streaming stops
>> for any reason, like a network glitch. Maybe that's a tradeoff you
>> want, but I'm asking because that point isn't clear to many people.
> If there's a network glitch, it'd probably affect networked client
> connections as well, so it would mean no extra degration of service.

Agreed.

I think the network glitch example is too general, it could affect any
part of the whole network. Even just the connection between the master
and the standby, in which case all client connections would keep up.

Let's quickly think about that scenario. AFAIU in such a case, the
standby would continue to answer read-only queries, independent of what
the master does, right? Or does the standby stop processing read-only
queries in case it looses connection to the master?

It seems to me the later is required, if we let the master continue to
commit transactions. Otherwise the standby would serve stale data to its
clients without knowing.

Given that scenario, I'd clearly favor a master that stops committing
new transactions, but allow both (i.e. master and standbies) to continue
answering read-only queries.

Regards

Markus Wanner