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help / color / mirror / Atom feedFrom: Nathan Bossart <nathandbossart@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Melih Mutlu <m.melihmutlu@gmail.com>
Cc: Thomas Munro <thomas.munro@gmail.com>
Cc: Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>
Cc: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Subject: Re: wake up logical workers after ALTER SUBSCRIPTION
Date: Tue, 13 Dec 2022 16:01:45 -0800
Message-ID: <20221214000145.GA638663@nathanxps13> (raw)
In-Reply-To: <2550453.1670974328@sss.pgh.pa.us>
References: <CA+hUKGJXO6LUn3wTf3s0Z8DvgbQROxPTnJDHCsQrhbr3pF3g8Q@mail.gmail.com>
<20221130050441.GA1677223@nathanxps13>
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<CAGPVpCTUuKyxB5f3exgDMBRTivbN5uHVkD=YfXmgznrdnwVOQw@mail.gmail.com>
<20221206192551.GA3078082@nathanxps13>
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<CAGPVpCTkdaOyBLXB435VXq0RA1cHLFQut7BPm6t8D4dsdiEXZQ@mail.gmail.com>
<20221207181145.GA3698731@nathanxps13>
<2550453.1670974328@sss.pgh.pa.us>
On Tue, Dec 13, 2022 at 06:32:08PM -0500, Tom Lane wrote:
> Before, there was up to 1 second (with multiple "SELECT count(1) = 0"
> probes from the test script) between the ALTER SUBSCRIPTION command
> and the "apply worker will restart" log entry. That wait is pretty
> well zapped, but instead now we're waiting hundreds of ms for the
> "apply worker has started" message.
>
> I've not chased it further than that, but I venture that the apply
> launcher also needs a kick in the pants, and/or there needs to be
> an interlock to ensure that it doesn't wake until after the old
> apply worker quits.
This is probably because the tests set wal_retrieve_retry_interval to
500ms. Lowering that to 1ms in Cluster.pm seems to wipe out this
particular wait, and the total src/test/subscription test time drops from
119 seconds to 95 seconds on my machine. This probably lowers the amount
of test coverage we get on the wal_retrieve_retry_interval code paths, but
if that's a concern, perhaps we should write a test specifically for
wal_retrieve_retry_interval.
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
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To: pgsql-hackers@postgresql.org
Cc: nathandbossart@gmail.com, tgl@sss.pgh.pa.us, m.melihmutlu@gmail.com, thomas.munro@gmail.com, kuroda.hayato@fujitsu.com
Subject: Re: wake up logical workers after ALTER SUBSCRIPTION
In-Reply-To: <20221214000145.GA638663@nathanxps13>
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