Re: Weird spikes in delay for async streaming replication on 9.1

Hi,

I posted this a couple of weeks ago and no response... I guess it's
quite mysterious.

Anyway, behavior is consistent.  It seems that long-running
transactions on the primary (even read-only ones, because in my case
it's a pg_dump) can block subsequent transactions from appearing on
the hot-standby until the first transaction finishes.  Is this a known
limitation?  I run 9.1; is it still present in 9.4?

Regards,

David.

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> I have a monitoring script that tests the actual delay for a
> transaction on the master to appear on the hot-standby.  Every few
> minutes, my script runs an update on the master and then sits in a
> loop checking how long it takes to appear on the hot-standby.  99% of
> the time, it's less than a second.

> But every once in a while, the time spikes dramatically, to hundreds
> or thousands of seconds, and that's too long... the delay-tolerant
> queries are not *that* delay-tolerant, so we switch to sending them
> all to the master.

> See the graph: http://ibin.co/1rdm4ekiWmpM

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