From 0188bb82531f1b0ae3648fb81a4bd4a4f6242127 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Wed, 24 Jun 2020 14:15:17 -0400
Subject: [PATCH] Save slot's restart_lsn when invalidated due to size
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We put it aside as invalidated_at, which let us show "lost" in
pg_replication slot. Prior to this change, the state value was reported
as NULL.
Backpatch to 13.
Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/20200617.101707.1735599255100002667.horikyota.ntt@gmail.com
Discussion: https://postgr.es/m/20200407.120905.1507671100168805403.horikyota.ntt@gmail.com
---
src/backend/replication/slot.c | 1 +
src/backend/replication/slotfuncs.c | 11 ++++++++++-
src/include/access/xlog.h | 2 +-
src/include/replication/slot.h | 3 +++
src/test/recovery/t/019_replslot_limit.pl | 2 +-
5 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index a7bbcf3499..e8761f3a18 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -1226,6 +1226,7 @@ restart:
(uint32) restart_lsn)));
SpinLockAcquire(&s->mutex);
+ s->data.invalidated_at = s->data.restart_lsn;
s->data.restart_lsn = InvalidXLogRecPtr;
SpinLockRelease(&s->mutex);
ReplicationSlotRelease();
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index 06e4955de7..3fc54cb9ba 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -283,6 +283,7 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
bool nulls[PG_GET_REPLICATION_SLOTS_COLS];
WALAvailability walstate;
XLogSegNo last_removed_seg;
+ XLogRecPtr targetLSN;
int i;
if (!slot->in_use)
@@ -342,7 +343,15 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
else
nulls[i++] = true;
- walstate = GetWALAvailability(slot_contents.data.restart_lsn);
+ /*
+ * Report availability from invalidated_at when the slot has been
+ * invalidated; otherwise slots would appear as invalid without any
+ * more clues as to what happened.
+ */
+ targetLSN = XLogRecPtrIsInvalid(slot_contents.data.restart_lsn) ?
+ slot_contents.data.invalidated_at :
+ slot_contents.data.restart_lsn;
+ walstate = GetWALAvailability(targetLSN);
switch (walstate)
{
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 347a38f57c..9702dce98a 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -326,7 +326,7 @@ extern void ShutdownXLOG(int code, Datum arg);
extern void InitXLOGAccess(void);
extern void CreateCheckPoint(int flags);
extern bool CreateRestartPoint(int flags);
-extern WALAvailability GetWALAvailability(XLogRecPtr restart_lsn);
+extern WALAvailability GetWALAvailability(XLogRecPtr targetLSN);
extern XLogRecPtr CalculateMaxmumSafeLSN(void);
extern void XLogPutNextOid(Oid nextOid);
extern XLogRecPtr XLogRestorePoint(const char *rpName);
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 917876010e..31362585ec 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -79,6 +79,9 @@ typedef struct ReplicationSlotPersistentData
/* oldest LSN that might be required by this replication slot */
XLogRecPtr restart_lsn;
+ /* restart_lsn is copied here when the slot is invalidated */
+ XLogRecPtr invalidated_at;
+
/*
* Oldest LSN that the client has acked receipt for. This is used as the
* start_lsn point in case the client doesn't specify one, and also as a
diff --git a/src/test/recovery/t/019_replslot_limit.pl b/src/test/recovery/t/019_replslot_limit.pl
index cba7df920c..f1be984cc9 100644
--- a/src/test/recovery/t/019_replslot_limit.pl
+++ b/src/test/recovery/t/019_replslot_limit.pl
@@ -186,7 +186,7 @@ ok( find_in_log(
$result = $node_master->safe_psql('postgres',
"SELECT slot_name, active, restart_lsn IS NULL, wal_status, min_safe_lsn FROM pg_replication_slots WHERE slot_name = 'rep1'"
);
-is($result, "rep1|f|t||", 'check that the slot became inactive');
+is($result, "rep1|f|t|lost|", 'check that the slot became inactive');
# The standby no longer can connect to the master
$logstart = get_log_size($node_standby);