Re: [BUGS] BUG #14821: idle_in_transaction_session_timeout sometimes gets ignored when statement timeout is pending

Started by Lukas Fittlover 8 years ago3 messageshackersbugs
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#1Lukas Fittl
lukas@fittl.com
hackersbugs

Hi,

As per the bug report at
/messages/by-id/20170921010956.17345.61461@wrigleys.postgresql.org
it seems that the query cancellation holdoff logic in ProcessInterrupts is
a bit overly aggressive in keeping other interrupts from running.

In particular I've seen an issue in the wild where
idle_in_transaction_session_timeout did not get triggered because
the HOLD_CANCEL_INTERRUPTS() in SocketBackend wraps around a pq_getbyte()
call, and so ProcessInterrupts doesn't do anything when it gets called
because the query cancel holdoff counter is positive.

Andres suggested the following re-ordering of the logic on -bugs:

On Wed, Sep 20, 2017 at 6:29 PM, Andres Freund <andres@anarazel.de> wrote:

if (QueryCancelPending && QueryCancelHoldoffCount != 0)
{
/* rearm */
}
else if (QueryCancelPending)
{
/* handle interrupt */
}

Which is implemented in the attached patch.

Unless someone wants to pick this up right away, I'll register it in the
next commitfest tomorrow.

Best,
Lukas

--
Lukas Fittl

Attachments:

0001-Only-skip-query-cancel-itself-when-query-cancel-hold.patchapplication/octet-stream; name=0001-Only-skip-query-cancel-itself-when-query-cancel-hold.patchDownload+15-18
#2Andres Freund
andres@anarazel.de
In reply to: Lukas Fittl (#1)
hackersbugs
Re: [HACKERS] Re: BUG #14821: idle_in_transaction_session_timeout sometimes gets ignored when statement timeout is pending

Hi,

On 2017-09-20 20:27:05 -0700, Lukas Fittl wrote:

As per the bug report at
/messages/by-id/20170921010956.17345.61461@wrigleys.postgresql.org
it seems that the query cancellation holdoff logic in ProcessInterrupts is
a bit overly aggressive in keeping other interrupts from running.

In particular I've seen an issue in the wild where
idle_in_transaction_session_timeout did not get triggered because
the HOLD_CANCEL_INTERRUPTS() in SocketBackend wraps around a pq_getbyte()
call, and so ProcessInterrupts doesn't do anything when it gets called
because the query cancel holdoff counter is positive.

Andres suggested the following re-ordering of the logic on -bugs:

I've pushed this. Thanks for the report & fix!

Greetings,

Andres Freund

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#3Lukas Fittl
lukas@fittl.com
In reply to: Andres Freund (#2)
hackersbugs
Re: [HACKERS] Re: BUG #14821: idle_in_transaction_session_timeout sometimes gets ignored when statement timeout is pending

On Wed, Oct 11, 2017 at 2:11 PM Andres Freund <andres@anarazel.de> wrote:

I've pushed this. Thanks for the report & fix!

Excellent, thanks!

Best,
Lukas
--
Lukas Fittl