Hi,
On 7/11/22 8:18 AM, Drouvot, Bertrand wrote:
> Hi,
>
> On 7/7/22 10:10 PM, Tom Lane wrote:
>> Joe Conway <mail@joeconway.com> writes:
>>> It isn't clear to me if having a hook in the timeout handler is a
>>> nonstarter -- perhaps a comment with suitable warning for prospective
>>> extension authors is enough? Anyone else want to weigh in on this issue
>>> specifically?
>> It doesn't seem like a great place for a hook, because the list of stuff
>> you could safely do there would be mighty short, possibly the empty set.
>> Write to shared memory? Not too safe. Write to a file? Even less.
>> Write to local memory? Pointless, because we're about to _exit(1).
>> Pretty much anything I can think of that you'd want to do is something
>> we've already decided the core code can't safely do, and putting it
>> in a hook won't make it safer.
>>
>> If someone wants to argue for this hook, I'd like to see a credible
>> example of a *safe* use-case, keeping in mind the points raised in
>> the comments in BackendInitialize and process_startup_packet_die.
>
> The use case would be to increment a counter in shared memory (or most
> probably within an hash table) to reflect the number of times a
> startup packet timeout occurred.
>
> Reading the comments in/related to BackendInitialize() I understand
> that's definitely not safe to write in shared memory for the
> EXEC_BACKEND case, but wouldn't it be safe for the non EXEC_BACKEND case?
>
> BTW, it makes me realize that the hook being fired in the bad startup
> packet case:
>
> /*
> * Stop here if it was bad or a cancel packet.
> ProcessStartupPacket
> * already did any appropriate error reporting.
> */
> if (status != STATUS_OK)
> + {
> + if (FailedConnection_hook)
> + (*FailedConnection_hook)
> (FCET_BAD_STARTUP_PACKET, port);
> proc_exit(0);
> + }
>
> is not safe for the EXEC_BACKEND case.
>
What about the idea to trigger the hook for the STARTUP PACKET TIMEOUT
and BAD STARTUP PACKET only for the non EXEC_BACKEND/Windows cases?
I'm tempted to think it's better to have some cases where one could
benefit from the hook as opposed to none.
Thoughts?
Regards,
--
Bertrand Drouvot
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