Re: Timeout failure in 019_replslot_limit.pl

On Fri, Sep 17, 2021 at 08:41:00PM -0700, Noah Misch wrote:
> If this fixes things for the OP, I'd like it slightly better than the "ps"
> approach. It's less robust, but I like the brevity.
>
> Another alternative might be to have walreceiver reach walsender via a proxy
> Perl script. Then, make that proxy able to accept an instruction to pause
> passing data until further notice. However, I like two of your options better
> than this one.

Could it be possible to rely on a combination of wait events set in WAL
senders and pg_stat_replication to assume that a WAL sender is in a
stopped state? I would think about something like that in the top of
my mind (perhaps this would need 2 WAL senders, one stopped and one
still running):
1) SIGSTOP WAL sender 1.
2) Check WAL sender 1 is in WalSenderMain. If not retry 1) after a
SIGCONT.
3) Generate some WAL, and look at pg_stat_replication to see if there
has been some progress in 1), but that 2) is done.
--
Michael