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Track last_inactive_time in pg_replication_slots.

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This commit adds a new property called last_inactive_time for slots. It is
set to 0 whenever a slot is made active/acquired and set to the current
timestamp whenever the slot is inactive/released or restored from the disk.
Note that we don't set the last_inactive_time for the slots currently being
synced from the primary to the standby because such slots are typically
inactive as decoding is not allowed on those.

The 'last_inactive_time' will be useful on production servers to debug and
analyze inactive replication slots. It will also help to know the lifetime
of a replication slot - one can know how long a streaming standby, logical
subscriber, or replication slot consumer is down.

The 'last_inactive_time' will also be useful to implement inactive
timeout-based replication slot invalidation in a future commit.

Author: Bharath Rupireddy
Reviewed-by: Bertrand Drouvot, Amit Kapila, Shveta Malik
Discussion: https://www.postgresql.org/message-id/CALj2ACW4aUe-_uFQOjdWCEN-xXoLGhmvRFnL8SNw_TZ5nJe+aw@mail.gmail.com
This commit is contained in:
Amit Kapila
2024-03-25 16:34:33 +05:30
parent 0f7863afef
commit a11f330b55
9 changed files with 213 additions and 6 deletions
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35
src/backend/replication/slot.c
View File

@ -409,6 +409,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
slot->candidate_restart_valid = InvalidXLogRecPtr;
slot->candidate_restart_lsn = InvalidXLogRecPtr;
slot->last_saved_confirmed_flush = InvalidXLogRecPtr;
slot->last_inactive_time = 0;
/*
* Create the slot on disk. We haven't actually marked the slot allocated
@ -622,6 +623,11 @@ retry:
if (SlotIsLogical(s))
pgstat_acquire_replslot(s);
/* Reset the last inactive time as the slot is active now. */
SpinLockAcquire(&s->mutex);
s->last_inactive_time = 0;
SpinLockRelease(&s->mutex);
if (am_walsender)
{
ereport(log_replication_commands ? LOG : DEBUG1,
@ -645,6 +651,7 @@ ReplicationSlotRelease(void)
ReplicationSlot *slot = MyReplicationSlot;
char *slotname = NULL; /* keep compiler quiet */
bool is_logical = false; /* keep compiler quiet */
TimestampTz now = 0;
Assert(slot != NULL && slot->active_pid != 0);
@ -679,6 +686,15 @@ ReplicationSlotRelease(void)
ReplicationSlotsComputeRequiredXmin(false);
}
/*
* Set the last inactive time after marking the slot inactive. We don't set
* it for the slots currently being synced from the primary to the standby
* because such slots are typically inactive as decoding is not allowed on
* those.
*/
if (!(RecoveryInProgress() && slot->data.synced))
now = GetCurrentTimestamp();
if (slot->data.persistency == RS_PERSISTENT)
{
/*
@ -687,9 +703,16 @@ ReplicationSlotRelease(void)
*/
SpinLockAcquire(&slot->mutex);
slot->active_pid = 0;
slot->last_inactive_time = now;
SpinLockRelease(&slot->mutex);
ConditionVariableBroadcast(&slot->active_cv);
}
else
{
SpinLockAcquire(&slot->mutex);
slot->last_inactive_time = now;
SpinLockRelease(&slot->mutex);
}
MyReplicationSlot = NULL;
@ -2342,6 +2365,18 @@ RestoreSlotFromDisk(const char *name)
slot->in_use = true;
slot->active_pid = 0;
/*
* We set the last inactive time after loading the slot from the disk
* into memory. Whoever acquires the slot i.e. makes the slot active
* will reset it. We don't set it for the slots currently being synced
* from the primary to the standby because such slots are typically
* inactive as decoding is not allowed on those.
*/
if (!(RecoveryInProgress() && slot->data.synced))
slot->last_inactive_time = GetCurrentTimestamp();
else
slot->last_inactive_time = 0;
restored = true;
break;
}

7
src/backend/replication/slotfuncs.c
View File

@ -239,7 +239,7 @@ pg_drop_replication_slot(PG_FUNCTION_ARGS)
Datum
pg_get_replication_slots(PG_FUNCTION_ARGS)
{
#define PG_GET_REPLICATION_SLOTS_COLS 18
#define PG_GET_REPLICATION_SLOTS_COLS 19
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
XLogRecPtr currlsn;
int slotno;
@ -410,6 +410,11 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
values[i++] = BoolGetDatum(slot_contents.data.two_phase);
if (slot_contents.last_inactive_time > 0)
values[i++] = TimestampTzGetDatum(slot_contents.last_inactive_time);
else
nulls[i++] = true;
cause = slot_contents.data.invalidated;
if (SlotIsPhysical(&slot_contents))