Horton

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

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Kevin McKibbin <kevinmckibbin123@gmail.com>
Cc: pgsql-performance@lists.postgresql.org
Date: 2022-08-21T03:20:02Z
Lists: pgsql-performance 
Kevin McKibbin <kevinmckibbin123@gmail.com> writes:
> What's limiting my DB from allowing more connections?

> This is a sample of the output I'm getting, which repeats the error 52
> times (one for each failed connection)

> -bash-4.2$ pgbench -c 200 -j 200 -t 100 benchy
> ...
> connection to database "benchy" failed:
> could not connect to server: Resource temporarily unavailable
>         Is the server running locally and accepting
>         connections on Unix domain socket
> "/var/run/postgresql/.s.PGSQL.5432"?

This is apparently a client-side failure not a server-side failure
(you could confirm that by seeing whether any corresponding
failure shows up in the postmaster log).  That means that the
kernel wouldn't honor pgbench's attempt to open a connection,
which implies you haven't provisioned enough networking resources
to support the number of connections you want.  Since you haven't
mentioned what platform this is on, it's impossible to say more
than that --- but it doesn't look like Postgres configuration
settings are at issue at all.

			regards, tom lane

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