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

On Sat, Mar 23, 2024 at 11:27 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> How about adding the test in 019_replslot_limit? It is not a direct
> fit but I feel later we can even add 'invalid_timeout' related tests
> in this file which will use last_inactive_time feature.

I'm thinking the other way. Now, the new TAP file 043_replslot_misc.pl
can have last_inactive_time tests, and later invalid_timeout ones too.
This way 019_replslot_limit.pl is not cluttered.

> It is also
> possible that some of the tests added by the 'invalid_timeout' feature
> will obviate the need for some of these tests.

Might be. But, I prefer to keep both these tests separate but in the
same file 043_replslot_misc.pl. Because we cover some corner cases the
last_inactive_time is set upon loading the slot from disk.

> Review of v15
> ==============
> 1.
> @@ -1026,7 +1026,8 @@ CREATE VIEW pg_replication_slots AS
>              L.conflicting,
>              L.invalidation_reason,
>              L.failover,
> -            L.synced
> +            L.synced,
> +            L.last_inactive_time
>      FROM pg_get_replication_slots() AS L
>
> As mentioned previously, let's keep these new fields before
> conflicting and after two_phase.

Sorry, I forgot to notice that comment (out of a flood of comments
really :)). Now, done that way.

> 2.
> +# Get last_inactive_time value after slot's creation. Note that the
> slot is still
> +# inactive unless it's used by the standby below.
> +my $last_inactive_time_1 = $primary->safe_psql('postgres',
> + qq(SELECT last_inactive_time FROM pg_replication_slots WHERE
> slot_name = '$sb_slot' AND last_inactive_time IS NOT NULL;)
> +);
>
> We should check $last_inactive_time_1 to be a valid value and add a
> similar check for logical slots.

That's taken care by the type cast we do, right? Isn't that enough?

is( $primary->safe_psql(
        'postgres',
        qq[SELECT last_inactive_time >
'$last_inactive_time'::timestamptz FROM pg_replication_slots WHERE
slot_name = '$sb_slot' AND last_inactive_time IS NOT NULL;]
    ),
    't',
    'last inactive time for an inactive physical slot is updated correctly');

For instance, setting last_inactive_time_1 to an invalid value fails
with the following error:

error running SQL: 'psql:<stdin>:1: ERROR:  invalid input syntax for
type timestamp with time zone: "foo"
LINE 1: SELECT last_inactive_time > 'foo'::timestamptz FROM pg_repli...

> 3. BTW, why don't we set last_inactive_time for temporary slots
> (RS_TEMPORARY) as well? Don't we even invalidate temporary slots? If
> so, then I think we should set last_inactive_time for those as well
> and later allow them to be invalidated based on timeout parameter.

WFM. Done that way.

Please see the attached v16 patch.

--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com