Re: Introduce XID age and inactive timeout based replication slot invalidation - Mailing list pgsql-hackers

On Tue, 4 Feb 2025 at 15:58, Nisha Moond <nisha.moond412@gmail.com> wrote:
>
> Here are the v68 patches, incorporating above as well as comments from [1].
>
Few comments:
1) Let's call TimestampDifferenceExceedsSeconds only if
idle_replication_slot_timeout_mins is set to avoid the
TimestampDifferenceExceedsSeconds function call and timestamp diff
calculation if not required:
+ if (CanInvalidateIdleSlot(s) &&
+ TimestampDifferenceExceedsSeconds(s->inactive_since, now,
+   idle_replication_slot_timeout_mins * SECS_PER_MINUTE))
+ {
+ invalidation_cause = cause;
+ inactive_since = s->inactive_since;
+ }
+ break;

2) Let's keep the prototype after TimestampDifferenceExceeds to keep
it consistent with the source file and will also make it easy to
search:
diff --git a/src/include/utils/timestamp.h b/src/include/utils/timestamp.h
index d26f023fb8..e1d05d6779 100644
--- a/src/include/utils/timestamp.h
+++ b/src/include/utils/timestamp.h
@@ -143,5 +143,8 @@ extern int  date2isoyear(int year, int mon, int mday);
 extern int     date2isoyearday(int year, int mon, int mday);

 extern bool TimestampTimestampTzRequiresRewrite(void);
+extern bool TimestampDifferenceExceedsSeconds(TimestampTz start_time,
+
                   TimestampTz stop_time,
+
                   int threshold_sec);

3)How about we change the below:
+#ifdef USE_INJECTION_POINTS
+
+                                               /*
+                                                * To test idle
timeout slot invalidation, if the
+                                                * slot-time-out-inval
injection point is attached,
+                                                * set inactive_since
to a very old timestamp (1
+                                                * microsecond since
epoch) to immediately invalidate
+                                                * the slot.
+                                                */
+                                               if
(IS_INJECTION_POINT_ATTACHED("slot-time-out-inval"))
+                                                       s->inactive_since = 1;
+#endif
to:
#ifdef USE_INJECTION_POINTS
/*
* To test idle timeout slot invalidation, if the
* slot-time-out-inval injection point is attached,
* set inactive_since to current time and invalidate the slot immediately.
*/
if (IS_INJECTION_POINT_ATTACHED("slot-time-out-inval") &&
idle_replication_slot_timeout_mins)
{
invalidation_cause = cause;
inactive_since = s->inactive_since = now;
}
#else
/*
* Check if the slot needs to be invalidated due to
* idle_replication_slot_timeout GUC.
*/
if (TimestampDifferenceExceedsSeconds(s->inactive_since, now,
  idle_replication_slot_timeout_mins * SECS_PER_MINUTE))
{
invalidation_cause = cause;
inactive_since = s->inactive_since;
}
#endif

We can just invalidate the slot directly without checking the time
difference if idle_replication_slot_timeout_mins is set and
inactive_since can hold the now value.

Regards,
Vignesh