[pgpool-general: 7956] Re: Pgpool ERROR: unable to read data from frontend

[Tatsuo Ishii]

> Hello,
> 
> Thank you for your comments. I tried your recommendations for logging
> settings and identified the application that is throwing this error
> message. This is pgmoon. The log  messages  look like:
> 
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> 
> ...
> 
> 2021-12-22 09:45:03: app pgmoon: pid 491: ERROR:  unable to read data
> from frontend
> 2021-12-22 09:45:03: app pgmoon: pid 491: DETAIL:  EOF encountered
> with frontend
> 2021-12-22 09:45:03: app pgmoon: pid 491: LOG:  frontend
> disconnection: session time: 0:01:05.042 user=user database=dbm
> host=10.2.12.3 port=41932
> 2021-12-22 09:45:11: app pgmoon: pid 51: ERROR:  unable to read data
> from frontend
> 2021-12-22 09:45:11: app pgmoon: pid 51: DETAIL:  EOF encountered with
> frontend
> 2021-12-22 09:45:11: app pgmoon: pid 51: LOG:  frontend disconnection:
> session time: 0:01:05.020 user=user database=dbm host=10.2.12.3
> port=42130
> 
> ...
> 
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> 
> Could we say that the error message is caused by frequent client
> disconnections?

No.

Googing "pgmoon" says it is written by Lua. I am not familiar with Lua
but I suspect that the driver just closes the communication socket
when an application requests to close the connection. Which is not
good from PostgreSQL frontend/backend protocol's point of view.

https://www.postgresql.org/docs/14/protocol-flow.html#id-1.10.5.7.10

"The normal, graceful termination procedure is that the frontend sends
a Terminate message and immediately closes the connection. On receipt
of this message, the backend closes the connection and terminates."

My guess is pgmoon does not follow the procedure described above.

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