[pgpool-general: 7939] Re: Pgpool does not accept new connections
Tatsuo Ishii
ishii at sraoss.co.jp
Thu Dec 16 08:53:43 JST 2021
> Hello,
>
> we have the problem, that Pgpool does not accept new connections when some
> longer running SQLs are on their way.
>
> We are using Pgpool 4.2.5 till now only for automated fail over and online
> recovery - connection pooling, load balancing, in memory query cache are
> switched off. PostgreSQL streaming replication is used.
>
> We can provoke the effect with a SQL like
>
> select field_a, field_b, pg_sleep(120)
> from table_a
> where field_a = 12345
>
> The statement simulates long running statements we are using.
>
> When we start the above statement 3 times or more with a delay of 1 second
> Pgpool does not accept new connections for some minutes. We do not get an
> error message or time out. Direct connections to Postgres are as fast as
> always.
>
> The effect exists in a 2-node cluster and in a degenerated, single machine
> cluster too.
It is possible that all pgpool child process are busy. You can check
by using pcp_proc_info command. Try:
pcp_proc_info -p [port number specified by pcp_port] -h localhost -v -a|grep Wait
If you get no lines at all, then all pgpool child process are occupied
by the long running queries. In this case you can:
- increase num_init_children (requires restarting pgpool)
- decrease the chance to issue the long running query.
Best reagards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp
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