Re: Introduce XID age and inactive timeout based replication slot invalidation

On Tue, Dec 24, 2024 at 10:37 PM Nisha Moond <nisha.moond412@gmail.com> wrote:
>
> On Fri, Dec 20, 2024 at 3:12 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>>
>> On Mon, Dec 16, 2024 at 4:10 PM Nisha Moond <nisha.moond412@gmail.com> wrote:
>> >
>> > Here is the v56 patch set with the above comments incorporated.
>> >
>>
>> Review comments:
>> ===============
>> 1.
>> + {
>> + {"idle_replication_slot_timeout", PGC_SIGHUP, REPLICATION_SENDING,
>> + gettext_noop("Sets the duration a replication slot can remain idle before "
>> + "it is invalidated."),
>> + NULL,
>> + GUC_UNIT_MS
>> + },
>> + &idle_replication_slot_timeout_ms,
>>
>> I think users are going to keep idele_slot timeout at least in hours.
>> So, millisecond seems the wrong choice to me. I suggest to keep the
>> units in minutes. I understand that writing a test would be
>> challenging as spending a minute or more on one test is not advisable.
>> But I don't see any test testing the other GUCs that are in minutes
>> (wal_summary_keep_time and log_rotation_age). The default value should
>> be one day.
>
>
> +1
> - Changed the GUC unit to "minute".
>
> Regarding the tests, we have two potential options:
>  1) Introduce an additional "debug_xx" GUC parameter with units of seconds or milliseconds, only for testing
purposes.
>  2) Skip writing tests for this, similar to other GUCs with units in minutes.
>
> IMO, adding an additional GUC just for testing may not be worthwhile. It's reasonable to proceed without the test.
>
> Thoughts?
>
> The attached v57 patch-set addresses all the comments. I have kept the test case in the patch for now, it takes 2-3
minutesto complete. 
>

Hi Nisha.

I think we are often too quick to throw out perfectly good tests.
Citing that some similar GUCs don't do testing as a reason to skip
them just seems to me like an example of "two wrongs don't make a
right".

There is a third option.

Keep the tests. Because they take excessive time to run, that simply
means you should run them *conditionally* based on the PG_TEST_EXTRA
environment variable so they don't impact the normal BF execution. The
documentation [1] says this env var is for "resource intensive" tests
-- AFAIK this is exactly the scenario we find ourselves in, so is
exactly what this env var was meant for.

Search other *.pl tests for PG_TEST_EXTRA to see some examples.

======
[1] https://www.postgresql.org/docs/17/regress-run.html

Kind Regards,
Peter Smith.
Fujitsu Australia