[pgpool-general: 850] Re: pgpool just hangs up after reaching "num_init_children" connections

Tatsuo Ishii ishii at postgresql.org
Fri Aug 3 15:00:11 JST 2012

> Yes, I read that FAQ. But I could also clearly observe that if it reaches
> "num_init_children" concurrent sessions, then it is not even allowing
> existing/already connected users a chance to disconnect, though. So, it
> becomes like a deadlock situation.

Not sure. Because I don't know your applications behavior.

> In order to set the right value for "num_init_children", we want to find out
> the *maximum connection* reached at any given timeframe from pgpool log, in
> case if we decide to increase "num_init_children" value.  Is it possible to
> determine this information from pgpool?

If you see the out put of ps command, it is easy to find out such a
situation because there would be no pgpool process something like this
if all pgpool child process are busy(or waiting for frontend exits):

apache   17236  0.0  0.0  63408  1220 ?        S    11:57   0:00 pgpool: wait for connection request    

However even if you want to find the number from pgpool log, it's
would be fairly easy. There's a counter in shared memory area:
Req_info->conn_counter. See connection_count_up(void):child.c.
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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