Re: Intermittent errors when fetching cursor rows on PostgreSQL 16

On 12/18/24 23:52, Enrico Schenone wrote:
> Good day, Adrian.
> First of all I thank-you for you answer.

> At the time the error occurs, dozens of other SQL sessions are active &
> running on DB server, and no-one is reporting any error at-all (not only
> fetch errors).
> This happens sometimes also in system with no (or low) stress situations.
>
> One of things I don't understand is why at client side I get the XX001
> error on the FETCH (normally the first fetch) while at server side I
> heve no error related to the fetch forward ?

Where are you fetching the client error messages from?

> Another is why in the meantime no other client application report an
> error, considering that there may be several parallel instances of the
> same client application ?
> And finally why after seconds or minutes the same process newly
> instantiated works with no more errors ?

Answers to this and the below is going to need the client code.

>
> I can suppose that the client closes the connection once got the XX001
> error, but I can't say why it receives this error while it is not
> reported at server side and not block i/o error is reported.
> Is it a false positive or what ?
>
> Four Js support said <We use the standard C API provided by the DB
> vendor. In the case of PostgreSQL, we use the C API client -
> https://www.postgresql.org/docs/current/libpq.html >
>
> At client side I have installed the following PostgreSQL packages ...
>
>     postgresql-client-16:amd64/jammy-pgdg 16.5-1.pgdg22.04+1
> upgradeable to 16.6-1.pgdg22.04+1
>     postgresql-client-common:all/jammy-pgdg 262.pgdg22.04+1 upgradeable
> to 267.pgdg22.04+1
>
> Best regards.
> Enrico
>
>
> *Enrico Schenone*
> Software Architect
>
> *Cleis Tech s.r.l.* - www.gruppocleis.it
> Sede di Genova, Via Paolo Emilio Bensa, 2 - 16124 Genova, ITALY
> Tel: +39-0104071400   Fax: +39-0104073276
> Mobile: +39-320 7709352
> E-mail: eschenone(at)cleistech(dot)it
>
> <https://gruppocleis.it><https://ibm.biz/BdqAJh>
>
> <https://ibm.biz/BdqAJh>
> <https://ibm.biz/BdqAJh>
> Il 19/12/24 00:11, Adrian Klaver ha scritto:
>> On 12/17/24 08:30, Enrico Schenone wrote:
>>> Good day.
>>> My name is Enrico Schenone, from Genoa, Italy.
>>> I'm a software achitect working at Cleis Tech - Genoa - Italy  -
>>> http://gruppocleis.it
>>> Me and my team are using PostgreSQL v12 to v16 on Debian 10-12 and
>>> Ubuntu Server 22.04 LTS with no-cluster configuration.
>>> Our applications are developed with 4Js Genero platform (classified
>>> as LCAP) - https://4js.com
>>>
>>> I whish to report an issue where I can't say if it happens at server
>>> or client side (or both as well).
>>
>> This:
>>
>> "unexpected EOF on client connection "
>>
>> makes me believe this is on client side.
>>
>> To be clear the client is running on Ubuntu Server 22.04, correct?
>>
>> Have you looked at the OS system log for relevant entries at the time
>> the error occurs?
>>
>> If so what are they?
>>
>> This only happens in production environment, is there anything in it
>> that is materially different from where you ran the test below?
>>
>>
>>> Hoping you can help me or address to someone who can do it.
>>> Thanks in advance.
>>> Enrico
>>> --
>>>
>>> *Enrico Schenone*
>>> Software Architect
>>>
>>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com