From: Nathan Bossart <nathandbossart@gmail.com>
To: Magnus Hagander <magnus@hagander.net>
Cc: Michael Paquier <michael@paquier.xyz>
Cc: Bossart, Nathan <bossartn@amazon.com>
Cc: Fujii Masao <masao.fujii@oss.nttdata.com>
Cc: Justin Pryzby <pryzby@telsasoft.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: Mark Dilger <mark.dilger@enterprisedb.com>
Cc: Don Seiler <don@seiler.us>
Cc: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Subject: Re: Estimating HugePages Requirements?
Date: Thu, 24 Mar 2022 13:31:08 -0700
Message-ID: <20220324203108.GB1855897@nathanxps13> (raw)
In-Reply-To: <CABUevEyExSDrtZ4wU19iX4yvgExR1EpjFKB4ExFQDgTAvAHFyg@mail.gmail.com>
References: <YTmLQtpUSK77mlGT@paquier.xyz>
<YTmMLtoLEAjMuRSm@paquier.xyz>
<6AE0285D-0917-4C05-B6AA-4AEDD2FCBA52@amazon.com>
<CABUevEweO_ZxTQox=QoO8e3rZQm9qFVU+zdoQvazTH9F7HpdEQ@mail.gmail.com>
<20220314173417.GA1020555@nathanxps13>
<Yi/82cqnpKkZsOjI@paquier.xyz>
<CABUevExgoKMNveD5SvFWOYA4MQvPkDmGxY7DkVRASJED4gBYog@mail.gmail.com>
<20220315224439.GA1133771@nathanxps13>
<Yjq9bJe28newGZaK@paquier.xyz>
<CABUevEyExSDrtZ4wU19iX4yvgExR1EpjFKB4ExFQDgTAvAHFyg@mail.gmail.com>
On Thu, Mar 24, 2022 at 02:07:26PM +0100, Magnus Hagander wrote:
> On Wed, Mar 23, 2022 at 7:25 AM Michael Paquier <michael@paquier.xyz> wrote:
>> On Tue, Mar 15, 2022 at 03:44:39PM -0700, Nathan Bossart wrote:
>> > A simple approach could be to just set log_min_messages to PANIC before
>> > exiting. I've attached a patch for this. With this patch, we'll still see
>> > a FATAL if we try to use 'postgres -C' for a runtime-computed GUC on a
>> > running server, and there will be no extra output as long as the user sets
>> > log_min_messages to INFO or higher (i.e., not a DEBUG* value). For
>> > comparison, 'postgres -C' for a non-runtime-computed GUC does not emit
>> > extra output as long as the user sets log_min_messages to DEBUG2 or higher.
>>
>> > puts(config_val ? config_val : "");
>> > +
>> > + /* don't emit shutdown messages */
>> > + SetConfigOption("log_min_messages", "PANIC", PGC_INTERNAL, PGC_S_OVERRIDE);
>> > +
>> > ExitPostmaster(0);
>>
>> That's fancy, but I don't like that much. And this would not protect
>> either against any messages generated before this code path, either,
>
> But neither would the suggestion of redirecting stderr to /dev/null.
> In fact, doing the redirect it will *also* throw away any FATAL that
> happens. In fact, using the 2>/dev/null method, we *also* remove the
> message that says there's another postmaster running in this
> directory, which is strictly worse than the override of
> log_min_messages.
>
> That said, the redirect can be removed without recompiling postgres,
> so it is probably still hte better choice as a temporary workaround.
> But we should really look into getting a better solution in place once
> we start on 16.
A couple of other options to consider:
1) Always set log_min_messages to WARNING/ERROR/FATAL for 'postgres -C'.
We might need some special logic for handling the case where the user is
inspecting the log_min_messages parameter. With this approach, you'd
probably never get extra output unless something was wrong (e.g., database
already running when inspecting a runtime-computed GUC). Also, this would
silence any extra output that you might see today with non-runtime-computed
GUCs.
2) Add some way to skip just the shutdown message (e.g., a variable set
when output_config_variable is true). With this approach, you wouldn't get
extra output by default, but you still might if log_min_messages is set to
something like DEBUG3. This wouldn't impact any extra output that you see
today with non-runtime-computed GUCs.
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
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Cc: nathandbossart@gmail.com, magnus@hagander.net, michael@paquier.xyz, bossartn@amazon.com, masao.fujii@oss.nttdata.com, pryzby@telsasoft.com, andres@anarazel.de, mark.dilger@enterprisedb.com, don@seiler.us, pgsql-hackers@postgresql.org
Subject: Re: Estimating HugePages Requirements?
In-Reply-To: <20220324203108.GB1855897@nathanxps13>
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