Re: Can a long running procedure detect when smart shutdown is pending?

Στις 6/7/24 09:22, ο/η Pavel Stehule έγραψε:
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> so 6. 7. 2024 v 8:19 odesílatel Pavel Stehule
> <pavel(dot)stehule(at)gmail(dot)com> napsal:
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> so 6. 7. 2024 v 8:06 odesílatel Achilleas Mantzios
> <a(dot)mantzios(at)cloud(dot)gatewaynet(dot)com> napsal:
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> Στις 6/7/24 08:39, ο/η Pavel Stehule έγραψε:
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>> so 6. 7. 2024 v 1:36 odesílatel Dennis White
>> <dwhite(at)seawardmoon(dot)com> napsal:
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>> Thanks for responding.
>> This will be a stored procedure written in plpgsql that's
>> kicked off by pg_cron.
>> I wasn't sure a normal smart shutdown would stop it.
>>
>>
>> shutdown try to cancel any query. The plpgsql routine should
>> be canceled without problems.
> fast mode will have this effect. smart mode not, from my
> testing. The running queries do not get interrupted in smart
> shutdown.
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>
> ok
>
> but you can set timeout there. It doesn't help?
>
> You can create some aux postgresql connection with specific app
> name, and then you can monitor if this process still live from
> pg_stat_activity
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> one process
>
> connect
> set application_name to 'xxxx';
>
> second process
> if not exists(select * from pg_stat_activity where appname =
> 'xxxx') then
>   exit
> end if;
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>
> sorry - it cannot to help too
>
> probably only one solution can be to write some extension and read
> some internal state

One idea was to have a process reading the log for " received smart
shutdown request " and then send a

NOTIFY shutdown_channel, 'shutdown in progress'

The question I have not yet answered is how to get the asynchronous
notification from within plpgsql. I mean this is possible with python or
Go or Java / JDBC or some other programming language , but cannot seem
to find anything in plpgsql .

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>> Thanks
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>> On Fri, Jul 5, 2024 at 4:57 PM Achilleas Mantzios
>> <a(dot)mantzios(at)cloud(dot)gatewaynet(dot)com> wrote:
>>
>> Στις 5/7/24 21:12, ο/η Dennis White έγραψε:
>>> My project's DB has a mutli-step stored procedure
>>> using Transaction Control that may take 30 minutes
>>> or more to complete.
>>> I am curious if there is a way to make it more smart
>>> shutdown friendly so it can stop between steps?
>>>
>>> We are using both PG 14 and PG 16 on Rhel 8.
>>> Pardon me if it's obvious but is there a function to
>>> call or a table that could be checked after a commit
>>> within the procedure to determine a shutdown is pending?
>>
>> Maybe somehow checking the log for a message like :
>>
>> received smart shutdown request
>>
>> Or use tail_n_mail against the log and then implement
>> some logic using NOTIFY , ideally you want your
>> procedure to be interrupted rather than do polling.
>>
>>>
>>> Thanks,
>>> Dennis
>>
>> --
>> Achilleas Mantzios
>> IT DEV - HEAD
>> IT DEPT
>> Dynacom Tankers Mgmt (as agents only)
>>
> --
> Achilleas Mantzios
> IT DEV - HEAD
> IT DEPT
> Dynacom Tankers Mgmt (as agents only)
>
--
Achilleas Mantzios
IT DEV - HEAD
IT DEPT
Dynacom Tankers Mgmt (as agents only)