One more thing:
Am Sonntag, den 09.04.2017, 11:00 +0200 schrieb Michael Banck:
> Also, 9.6 had remote_apply, which is arguably at least as important as
> quorum commit, as it means querying the standby right afterwards will
> result in the expected behavior; if we just had quorum_commit with
> synchronous_commit merely to 'on', querying the sync standbys
> immediately after a commit might still return the old rows (the new rows
> are written to WAL so are crash-safe, but are not necessarily replayed
> yet), to the best of my knowledge. So quorum commit extends remote_apply
> to multiple standbys.
>
> Finally, note that even though libpq now can handle mutiple hosts in the
> connection string, it won't load-balance between those (in contrast to
> pgJDBC BTW, which can do load balancing), but just use the next one if
> the current connection goes away (i.e. failover). Load-Balancing still
> needs external tooling for now.
Assuming we will get (connection-based) load balancing for 11 (educated
guess - it should be pretty easy to add this now that we support
multiple hosts) and also causal reads[1,2] (submitted for 10, but bumped
to 11), this scale-out story will be a lot more coherent in my opinion;
so we could focus on other high impact stories for 10 and leave
scale-out for 11.
Michael
[1] https://commitfest.postgresql.org/14/951/
[2] https://www.postgresql.org/message-id/CAEepm=1iiEzCVLD=RoBgtZSyEY1CR-Et7fRc9prCZ9MuTz3pWg@mail.gmail.com
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