Обсуждение: Limit transaction lifetime

On 06/03/2020 14:24, Andrei Zhidenkov wrote:
> Is there a way to limit a transaction lifetime in PostgreSQL? I could 
> use `idle_in_transaction_session_timeout` parameter but it applies only 
> to IDLE transactions. However, I want to rollback any transaction that 
> executes more than specified period of time.
> 
> --
> 
> With best regards, Andrei Zhidenkov.

If it's a single command you're trying to limit `SET statement_timeout 
TO <whatever>` should do the trick.


If you want it based on the session's cumulative statement time, off the 
top of my head I can't think of anything in vanilla PG without using 
executor hooks (that requires some coding).


If the queries that worry you are long-lived, you might be able to get 
by with a scheduled process checking against pg_stat_activity (eg: 
age(query_start)) and adding the current query's run-time to some 
per-session total, but it's an highly inaccurate process.




-- 
Regards

Fabio Ugo Venchiarutti
OSPCFC Network Engineering Dpt.
Ocado Technology

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> If it's a single command you're trying to limit `SET statement_timeout TO <whatever>` should do the trick.

This will set only statement timeout but won’t work for long transactions that contain a lot of short statements.

> If you want it based on the session's cumulative statement time, off the top of my head I can't think of anything in
vanillaPG without using executor hooks (that requires some coding). 

Yes, that’s exactly I want to do.

> If the queries that worry you are long-lived, you might be able to get by with a scheduled process checking against
pg_stat_activity(eg: age(query_start)) and adding the current query's run-time to some per-session total, but it's an
highlyinaccurate process. 

I think in my case I should check `xact_start`, because not every query initiates a new transaction.

On 06/03/2020 16:14, Andrei Zhidenkov wrote:
>
>> If it's a single command you're trying to limit `SET statement_timeout TO <whatever>` should do the trick.
>
> This will set only statement timeout but won’t work for long transactions that contain a lot of short statements.
>
>> If you want it based on the session's cumulative statement time, off the top of my head I can't think of anything in
vanillaPG without using executor hooks (that requires some coding). 
>
> Yes, that’s exactly I want to do.
>
>> If the queries that worry you are long-lived, you might be able to get by with a scheduled process checking against
pg_stat_activity(eg: age(query_start)) and adding the current query's run-time to some per-session total, but it's an
highlyinaccurate process. 
>
> I think in my case I should check `xact_start`, because not every query initiates a new transaction.
That way you'd also be counting in time a given transaction spent
idling, which IME is one of the biggest source of concurrency headaches
if it's holding locks while doing nothing.
If your use case is unaffected by that, that'd be good news for you.





--
Regards

Fabio Ugo Venchiarutti
OSPCFC Network Engineering Dpt.
Ocado Technology

--


Notice:
This email is confidential and may contain copyright material of
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Ocado Group.

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your responsibility to scan this message for viruses.

References to the
"Ocado Group" are to Ocado Group plc (registered in England and Wales with
number 7098618) and its subsidiary undertakings (as that expression is
defined in the Companies Act 2006) from time to time. The registered office
of Ocado Group plc is Buildings One & Two, Trident Place, Mosquito Way,
Hatfield, Hertfordshire, AL10 9UL.