[pgpool-general: 8203] Re: unable to read data from frontend

Tatsuo Ishii ishii at sraoss.co.jp
Thu Jun 2 21:47:34 JST 2022

> Hello,
> Thank you for reply.
> In pgpool source code I found this error message raising  in
> "utils\pool_stream.c":
>             else
>             {
>                 /*
>                  * if backend offers authentication method, frontend
> could
>                  * close connection
>                  */
>                 ereport(FRONTEND_ERROR,
>                         (errmsg("unable to read data from frontend"),
>                          errdetail("EOF encountered with frontend")));
>             }
> I would like to understand the comment here - "if backend offers
> authentication method, frontend could close connection".
> Could you clarify comment of this error message?

The comment is somewhat misleading.

Long time ago Pgpool-II always offered the same auth method to
frontend as the backend offered. At that time the comment was correct
but nowadays Pgpool-II can offer different auth method to frontend
than the backend offers (for example, it is possible that Pgpool-II is
authenticated by backend using md5, while Pgpool-II offers clear text
password auth to frontend). So it is not necessary for Pgpool-II to
offer the same auth method to frontend as the backend offers to

Anyway, if Pgpool-II offered certain auth method to frontend, and
frontend does not support the offered auth method, the frontend could
close the connection to Pgpool-II immediately. This could happen, for
example, if Pgpool-II offers scram-sha-256 auth, but the frontend is
old and lacks the support for scram-sha-256 auth.

> Regards,
>    Nikola
> On 02.06.2022 08:24, Tatsuo Ishii wrote:
>>> Hello,
>>> Pgpool works in Kubernetes with 3 replicas. Docker image
>>> pgpool/pgpool:4.2.2 is used.
>>> One of the clients of Pgpool is Kong API Gateway. Periodically the
>>> follow error log message is appeared in Pgpool log:
>>> -----------------------------
>>> pgmoon [10170] kong at kongdb |ERROR:  unable to read data from frontend
>>> pgmoon [10170] kong at kongdb |DETAIL:  EOF encountered with frontend
>>> -----------------------------
>>> pgmoon is a PostgreSQL client library that is used by Kong.
>>> My questions are:
>>> 1. Why is this error happening?
>> It has been already answered here:
>> https://www.pgpool.net/pipermail/pgpool-general/2021-December/008014.html
>>> 2. How I can fix it?
>> Ask the pgmoon developer to fix it.
>>> 3. How does this bug seriously affect the stability and performance of
>>> Pgpool?
>> There should be no concern about Pgpool stability. It may affect the
>> performance of Pgpool if the error happens too frequently though,
>> because of the extra logging of the error message.
>> Best reagards,
>> --
>> Tatsuo Ishii
>> SRA OSS, Inc. Japan
>> English: http://www.sraoss.co.jp/index_en.php
>> Japanese:http://www.sraoss.co.jp

More information about the pgpool-general mailing list