[pgpool-general: 8204] Re: unable to read data from frontend

Nikolay Mastilo (HM) nikm71 at hotmail.com
Thu Jun 2 21:51:46 JST 2022


I got it, thank you!

Regards,
   Nikola

02.06.2022 15:47, Tatsuo Ishii пишет:
>> 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
> Pgpool-II.
>
> 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


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