[pgpool-general: 7950] Re: Pgpool ERROR: unable to read data from frontend

[Tatsuo Ishii]

> Hello All,
> 
> Another question, if possible.
> 
> Pgpool constantly sends messages to the log:
> 2021-12-21 14:44:06: pid 206: ERROR: unable to read data from frontend
> 2021-12-21 14:44:06: pid 206: DETAIL: EOF encountered with frontend
> 
> Am I correct in understanding that it is trying to establish or verify
> communication with his client? Is it right?

No. This happens while pgpool is waiting for a message from frontend
(client). The log means frontend disconnects the socket without proper
step defined in the PostgreSQL protocol.

> Only it is not clear with which client. We have a dozen or more
> services working through Pgpool.
> 
> I tried to check by pid number using SHOW POOL_PROCESSES command. But
> most often there is an empty line under the number of such pid number
> I'm interested in.

It is possible that the process has gone.

> Could you tell me how to diagnose with which client service Pgpool has
> this problem.

You can use log_disconnections. By using this you could get the host name of client.

2021-12-22 09:00:07.613: psql pid 261093: ERROR:  unable to read data from frontend
2021-12-22 09:00:07.613: psql pid 261093: DETAIL:  EOF encountered with frontend
2021-12-22 09:00:07.613: psql pid 261093: LOG:  frontend disconnection: session time: 0:00:07.544 user=t-ishii database=test host=[local]

Also "%a" (application name) in log_line_prefix may be useful to know
which application was connecting.

Best reagards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp