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Track statistics for spilling of changes from ReorderBuffer.

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This adds the statistics about transactions spilled to disk from
ReorderBuffer. Users can query the pg_stat_replication_slots view to check
these stats and call pg_stat_reset_replication_slot to reset the stats of
a particular slot. Users can pass NULL in pg_stat_reset_replication_slot
to reset stats of all the slots.

This commit extends the statistics collector to track this information
about slots.

Author: Sawada Masahiko and Amit Kapila
Reviewed-by: Amit Kapila and Dilip Kumar
Discussion: https://postgr.es/m/CA+fd4k5_pPAYRTDrO2PbtTOe0eHQpBvuqmCr8ic39uTNmR49Eg@mail.gmail.com
This commit is contained in:
Amit Kapila
2020-10-08 09:09:08 +05:30
parent 8d2a01ae12
commit 9868167500
16 changed files with 700 additions and 8 deletions
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25
src/backend/replication/slot.c
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@@ -99,7 +99,6 @@ ReplicationSlot *MyReplicationSlot = NULL;
int max_replication_slots = 0; /* the maximum number of replication
* slots */
static ReplicationSlot *SearchNamedReplicationSlot(const char *name);
static int ReplicationSlotAcquireInternal(ReplicationSlot *slot,
const char *name, SlotAcquireBehavior behavior);
static void ReplicationSlotDropAcquired(void);
@@ -314,6 +313,15 @@ ReplicationSlotCreate(const char *name, bool db_specific,
LWLockRelease(ReplicationSlotControlLock);
/*
* Create statistics entry for the new logical slot. We don't collect any
* stats for physical slots, so no need to create an entry for the same.
* See ReplicationSlotDropPtr for why we need to do this before releasing
* ReplicationSlotAllocationLock.
*/
if (SlotIsLogical(slot))
pgstat_report_replslot(NameStr(slot->data.name), 0, 0, 0);
/*
* Now that the slot has been marked as in_use and active, it's safe to
* let somebody else try to allocate a slot.
@@ -331,7 +339,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
*
* The caller must hold ReplicationSlotControlLock in shared mode.
*/
static ReplicationSlot *
ReplicationSlot *
SearchNamedReplicationSlot(const char *name)
{
int i;
@@ -683,6 +691,19 @@ ReplicationSlotDropPtr(ReplicationSlot *slot)
ereport(WARNING,
(errmsg("could not remove directory \"%s\"", tmppath)));
/*
* Send a message to drop the replication slot to the stats collector.
* Since there is no guarantee of the order of message transfer on a UDP
* connection, it's possible that a message for creating a new slot
* reaches before a message for removing the old slot. We send the drop
* and create messages while holding ReplicationSlotAllocationLock to
* reduce that possibility. If the messages reached in reverse, we would
* lose one statistics update message. But the next update message will
* create the statistics for the replication slot.
*/
if (SlotIsLogical(slot))
pgstat_report_replslot_drop(NameStr(slot->data.name));
/*
* We release this at the very end, so that nobody starts trying to create
* a slot while we're still cleaning up the detritus of the old one.