Horton

Re: pgbench: could not connect to server: Resource temporarily unavailable

Thomas Munro <thomas.munro@gmail.com>

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From: Thomas Munro <thomas.munro@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andrew Dunstan <andrew@dunslane.net>, Kevin McKibbin <kevinmckibbin123@gmail.com>, pgsql-performance@lists.postgresql.org
Date: 2022-08-23T02:42:13Z
Lists: pgsql-performance 
On Tue, Aug 23, 2022 at 4:57 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> 0001 adds a para about how to raise the listen queue length.

+    service the requests, with those clients receiving unhelpful
+    connection failure errors such as <quote>Resource temporarily
+    unavailable</quote>.

LGTM but I guess I would add "... or Connection refused"?

> 0002 isn't quite related, but while writing 0001 I noticed a nearby
> use of /proc/sys/... which I thought should be converted to sysctl.
> IMO /proc/sys pretty much sucks, at least for documentation purposes,
> for multiple reasons:

+1

> 0003 removes PG_SOMAXCONN.  While doing that I noticed that this
> computation hadn't been touched throughout all the various
> changes fooling with exactly what gets counted in MaxBackends.
> I think the most appropriate definition for the listen queue
> length is now MaxConnections * 2, not MaxBackends * 2, because
> the other processes counted in MaxBackends don't correspond to
> incoming connections.

+1

> I propose 0003 for HEAD only, but the docs changes could be
> back-patched.

+1

Commits

  1. Doc: document possible need to raise kernel's somaxconn limit.

  2. Doc: prefer sysctl to /proc/sys in docs and comments.

  3. Remove our artificial PG_SOMAXCONN limit on listen queue length.

  4. Instead of believing SOMAXCONN from the system header files (which is