Track statistics for spilling of changes from ReorderBuffer.

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

1 files changed, 50 insertions, 2 deletions

diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 343eef507ea..a821ff4f158 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -56,6 +56,7 @@ typedef enum StatMsgType
 	PGSTAT_MTYPE_RESETSHAREDCOUNTER,
 	PGSTAT_MTYPE_RESETSINGLECOUNTER,
 	PGSTAT_MTYPE_RESETSLRUCOUNTER,
+	PGSTAT_MTYPE_RESETREPLSLOTCOUNTER,
 	PGSTAT_MTYPE_AUTOVAC_START,
 	PGSTAT_MTYPE_VACUUM,
 	PGSTAT_MTYPE_ANALYZE,
@@ -68,7 +69,8 @@ typedef enum StatMsgType
 	PGSTAT_MTYPE_RECOVERYCONFLICT,
 	PGSTAT_MTYPE_TEMPFILE,
 	PGSTAT_MTYPE_DEADLOCK,
-	PGSTAT_MTYPE_CHECKSUMFAILURE
+	PGSTAT_MTYPE_CHECKSUMFAILURE,
+	PGSTAT_MTYPE_REPLSLOT,
 } StatMsgType;
 
 /* ----------
@@ -359,6 +361,18 @@ typedef struct PgStat_MsgResetslrucounter
 } PgStat_MsgResetslrucounter;
 
 /* ----------
+ * PgStat_MsgResetreplslotcounter Sent by the backend to tell the collector
+ *								to reset replication slot counter(s)
+ * ----------
+ */
+typedef struct PgStat_MsgResetreplslotcounter
+{
+	PgStat_MsgHdr m_hdr;
+	char		m_slotname[NAMEDATALEN];
+	bool		clearall;
+} PgStat_MsgResetreplslotcounter;
+
+/* ----------
  * PgStat_MsgAutovacStart		Sent by the autovacuum daemon to signal
  *								that a database is going to be processed
  * ----------
@@ -466,6 +480,22 @@ typedef struct PgStat_MsgSLRU
 } PgStat_MsgSLRU;
 
 /* ----------
+ * PgStat_MsgReplSlot	Sent by a backend or a wal sender to update replication
+ *						slot statistics.
+ * ----------
+ */
+typedef struct PgStat_MsgReplSlot
+{
+	PgStat_MsgHdr m_hdr;
+	char		m_slotname[NAMEDATALEN];
+	bool		m_drop;
+	PgStat_Counter m_spill_txns;
+	PgStat_Counter m_spill_count;
+	PgStat_Counter m_spill_bytes;
+} PgStat_MsgReplSlot;
+
+
+/* ----------
  * PgStat_MsgRecoveryConflict	Sent by the backend upon recovery conflict
  * ----------
  */
@@ -603,6 +633,7 @@ typedef union PgStat_Msg
 	PgStat_MsgResetsharedcounter msg_resetsharedcounter;
 	PgStat_MsgResetsinglecounter msg_resetsinglecounter;
 	PgStat_MsgResetslrucounter msg_resetslrucounter;
+	PgStat_MsgResetreplslotcounter msg_resetreplslotcounter;
 	PgStat_MsgAutovacStart msg_autovacuum_start;
 	PgStat_MsgVacuum msg_vacuum;
 	PgStat_MsgAnalyze msg_analyze;
@@ -616,6 +647,7 @@ typedef union PgStat_Msg
 	PgStat_MsgDeadlock msg_deadlock;
 	PgStat_MsgTempFile msg_tempfile;
 	PgStat_MsgChecksumFailure msg_checksumfailure;
+	PgStat_MsgReplSlot msg_replslot;
 } PgStat_Msg;
 
 
@@ -627,7 +659,7 @@ typedef union PgStat_Msg
  * ------------------------------------------------------------
  */
 
-#define PGSTAT_FILE_FORMAT_ID	0x01A5BC9E
+#define PGSTAT_FILE_FORMAT_ID	0x01A5BC9F
 
 /* ----------
  * PgStat_StatDBEntry			The collector's data per database
@@ -782,6 +814,17 @@ typedef struct PgStat_SLRUStats
 	TimestampTz stat_reset_timestamp;
 } PgStat_SLRUStats;
 
+/*
+ * Replication slot statistics kept in the stats collector
+ */
+typedef struct PgStat_ReplSlotStats
+{
+	char		slotname[NAMEDATALEN];
+	PgStat_Counter spill_txns;
+	PgStat_Counter spill_count;
+	PgStat_Counter spill_bytes;
+	TimestampTz stat_reset_timestamp;
+} PgStat_ReplSlotStats;
 
 /* ----------
  * Backend states
@@ -1330,6 +1373,7 @@ extern void pgstat_reset_counters(void);
 extern void pgstat_reset_shared_counters(const char *);
 extern void pgstat_reset_single_counter(Oid objectid, PgStat_Single_Reset_Type type);
 extern void pgstat_reset_slru_counter(const char *);
+extern void pgstat_reset_replslot_counter(const char *name);
 
 extern void pgstat_report_autovac(Oid dboid);
 extern void pgstat_report_vacuum(Oid tableoid, bool shared,
@@ -1342,6 +1386,9 @@ extern void pgstat_report_recovery_conflict(int reason);
 extern void pgstat_report_deadlock(void);
 extern void pgstat_report_checksum_failures_in_db(Oid dboid, int failurecount);
 extern void pgstat_report_checksum_failure(void);
+extern void pgstat_report_replslot(const char *slotname, int spilltxns, int spillcount,
+								   int spillbytes);
+extern void pgstat_report_replslot_drop(const char *slotname);
 
 extern void pgstat_initialize(void);
 extern void pgstat_bestart(void);
@@ -1508,6 +1555,7 @@ extern PgStat_ArchiverStats *pgstat_fetch_stat_archiver(void);
 extern PgStat_GlobalStats *pgstat_fetch_global(void);
 extern PgStat_WalStats *pgstat_fetch_stat_wal(void);
 extern PgStat_SLRUStats *pgstat_fetch_slru(void);
+extern PgStat_ReplSlotStats *pgstat_fetch_replslot(int *nslots_p);
 
 extern void pgstat_count_slru_page_zeroed(int slru_idx);
 extern void pgstat_count_slru_page_hit(int slru_idx);