From e41aed674f35c63380175bb0e2dfa8dccfb2204d Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Wed, 6 Apr 2022 18:26:17 -0700 Subject: [PATCH] pgstat: revise replication slot API in preparation for shared memory stats. Previously the pgstat <-> replication slots API was done with on the basis of names. However, the upcoming move to storing stats in shared memory makes it more convenient to use a integer as key. Change the replication slot functions to take the slot rather than the slot name, and expose ReplicationSlotIndex() to compute the index of an replication slot. Special handling will be required for restarts, as the index is not stable across restarts. For now pgstat internally still uses names. Rename pgstat_report_replslot_{create,drop}() to pgstat_{create,drop}_replslot() to match the functions for other kinds of stats. Reviewed-By: Kyotaro Horiguchi Discussion: https://postgr.es/m/20220404041516.cctrvpadhuriawlq@alap3.anarazel.de --- src/backend/postmaster/pgstat.c | 10 +++++++++- src/backend/replication/logical/logical.c | 2 +- src/backend/replication/slot.c | 20 ++++++++++++++++++-- src/backend/utils/activity/pgstat_replslot.c | 13 ++++++++----- src/include/pgstat.h | 7 ++++--- src/include/replication/slot.h | 1 + 6 files changed, 41 insertions(+), 12 deletions(-) diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c index 13dee84059..8655b56c5e 100644 --- a/src/backend/postmaster/pgstat.c +++ b/src/backend/postmaster/pgstat.c @@ -862,7 +862,15 @@ pgstat_vacuum_stat(void) CHECK_FOR_INTERRUPTS(); if (SearchNamedReplicationSlot(NameStr(slotentry->slotname), true) == NULL) - pgstat_report_replslot_drop(NameStr(slotentry->slotname)); + { + PgStat_MsgReplSlot msg; + + pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_REPLSLOT); + namestrcpy(&msg.m_slotname, NameStr(slotentry->slotname)); + msg.m_create = false; + msg.m_drop = true; + pgstat_send(&msg, sizeof(PgStat_MsgReplSlot)); + } } } diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index e1f14aeecb..656ec8f555 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -1921,7 +1921,7 @@ UpdateDecodingStats(LogicalDecodingContext *ctx) repSlotStat.total_txns = rb->totalTxns; repSlotStat.total_bytes = rb->totalBytes; - pgstat_report_replslot(&repSlotStat); + pgstat_report_replslot(ctx->slot, &repSlotStat); rb->spillTxns = 0; rb->spillCount = 0; diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index ed4c8b3ad5..2217af70d4 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -356,7 +356,7 @@ ReplicationSlotCreate(const char *name, bool db_specific, * ReplicationSlotAllocationLock. */ if (SlotIsLogical(slot)) - pgstat_report_replslot_create(NameStr(slot->data.name)); + pgstat_create_replslot(slot); /* * Now that the slot has been marked as in_use and active, it's safe to @@ -399,6 +399,22 @@ SearchNamedReplicationSlot(const char *name, bool need_lock) return slot; } +/* + * Return the index of the replication slot in + * ReplicationSlotCtl->replication_slots. + * + * This is mainly useful to have an efficient key for storing replication slot + * stats. + */ +int +ReplicationSlotIndex(ReplicationSlot *slot) +{ + Assert(slot >= ReplicationSlotCtl->replication_slots && + slot < ReplicationSlotCtl->replication_slots + max_replication_slots); + + return slot - ReplicationSlotCtl->replication_slots; +} + /* * Find a previously created slot and mark it as used by this process. * @@ -746,7 +762,7 @@ ReplicationSlotDropPtr(ReplicationSlot *slot) * doesn't seem worth doing as in practice this won't happen frequently. */ if (SlotIsLogical(slot)) - pgstat_report_replslot_drop(NameStr(slot->data.name)); + pgstat_drop_replslot(slot); /* * We release this at the very end, so that nobody starts trying to create diff --git a/src/backend/utils/activity/pgstat_replslot.c b/src/backend/utils/activity/pgstat_replslot.c index cfaf8d546c..ceefc5d59b 100644 --- a/src/backend/utils/activity/pgstat_replslot.c +++ b/src/backend/utils/activity/pgstat_replslot.c @@ -69,7 +69,7 @@ pgstat_reset_replslot(const char *name) * Report replication slot statistics. */ void -pgstat_report_replslot(const PgStat_StatReplSlotEntry *repSlotStat) +pgstat_report_replslot(ReplicationSlot *slot, const PgStat_StatReplSlotEntry *repSlotStat) { PgStat_MsgReplSlot msg; @@ -93,14 +93,17 @@ pgstat_report_replslot(const PgStat_StatReplSlotEntry *repSlotStat) /* * Report replication slot creation. + * + * NB: This gets called with ReplicationSlotAllocationLock already held, be + * careful about calling back into slot.c. */ void -pgstat_report_replslot_create(const char *slotname) +pgstat_create_replslot(ReplicationSlot *slot) { PgStat_MsgReplSlot msg; pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_REPLSLOT); - namestrcpy(&msg.m_slotname, slotname); + namestrcpy(&msg.m_slotname, NameStr(slot->data.name)); msg.m_create = true; msg.m_drop = false; pgstat_send(&msg, sizeof(PgStat_MsgReplSlot)); @@ -110,12 +113,12 @@ pgstat_report_replslot_create(const char *slotname) * Report replication slot drop. */ void -pgstat_report_replslot_drop(const char *slotname) +pgstat_drop_replslot(ReplicationSlot *slot) { PgStat_MsgReplSlot msg; pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_REPLSLOT); - namestrcpy(&msg.m_slotname, slotname); + namestrcpy(&msg.m_slotname, NameStr(slot->data.name)); msg.m_create = false; msg.m_drop = true; pgstat_send(&msg, sizeof(PgStat_MsgReplSlot)); diff --git a/src/include/pgstat.h b/src/include/pgstat.h index 7981a81656..0c618e7710 100644 --- a/src/include/pgstat.h +++ b/src/include/pgstat.h @@ -1137,9 +1137,10 @@ extern PgStat_TableStatus *find_tabstat_entry(Oid rel_id); */ extern void pgstat_reset_replslot(const char *name); -extern void pgstat_report_replslot(const PgStat_StatReplSlotEntry *repSlotStat); -extern void pgstat_report_replslot_create(const char *slotname); -extern void pgstat_report_replslot_drop(const char *slotname); +struct ReplicationSlot; +extern void pgstat_report_replslot(struct ReplicationSlot *slot, const PgStat_StatReplSlotEntry *repSlotStat); +extern void pgstat_create_replslot(struct ReplicationSlot *slot); +extern void pgstat_drop_replslot(struct ReplicationSlot *slot); /* diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h index 24b30210c3..1ee63c4cf4 100644 --- a/src/include/replication/slot.h +++ b/src/include/replication/slot.h @@ -216,6 +216,7 @@ extern bool ReplicationSlotsCountDBSlots(Oid dboid, int *nslots, int *nactive); extern void ReplicationSlotsDropDBSlots(Oid dboid); extern bool InvalidateObsoleteReplicationSlots(XLogSegNo oldestSegno); extern ReplicationSlot *SearchNamedReplicationSlot(const char *name, bool need_lock); +extern int ReplicationSlotIndex(ReplicationSlot *slot); extern void ReplicationSlotNameForTablesync(Oid suboid, Oid relid, char *syncslotname, int szslot); extern void ReplicationSlotDropAtPubNode(WalReceiverConn *wrconn, char *slotname, bool missing_ok);