Re: failover vs. read only queries

Fujii Masao <masao(dot)fujii(at)gmail(dot)com> writes:
> When the trigger file is created while the recovery keeps
> waiting for the release of the lock by read only queries,
> it might take a very long time for the standby to become
> the master. The recovery cannot go ahead until those read
> only queries have gone away. This would increase the downtime
> at the failover, and degrade the high availability.

> To fix the problem, when the trigger file is found, I think
> that we should cancel all the running read only queries
> immediately (or forcibly use -1 as the max_standby_delay
> since that point) and make the recovery go ahead. If some
> people prefer queries over failover even when they create the
> trigger file, we can make the trigger behavior selectable in
> response to the content of the trigger file like pg_standby
> does.

> This problem looks like a bug, so I'd like to fix that for
> 9.0. But the amount of code change might not be small.
> Thought?

-1. This looks like 9.1 material to me, and besides I'm not even
convinced that what you propose is a good solution.

regards, tom lane