Add TAP tests to check replication slot advance during the checkpointREL_17_STABLE

The new tests verify that logical and physical replication slots are still
valid after an immediate restart on checkpoint completion when the slot was
advanced during the checkpoint.

This commit introduces two new injection points to make these tests possible:

* checkpoint-before-old-wal-removal - triggered in the checkpointer process
  just before old WAL segments cleanup;
* logical-replication-slot-advance-segment - triggered in
  LogicalConfirmReceivedLocation() when restart_lsn was changed enough to
  point to the next WAL segment.

Discussion: https://postgr.es/m/flat/1d12d2-67235980-35-19a406a0%4063439497
Author: Vitaly Davydov <v.davydov@postgrespro.ru>
Author: Tomas Vondra <tomas@vondra.me>
Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Backpatch-through: 17

2 files changed, 22 insertions, 0 deletions

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 3735a2e3dfd..a00786d40c8 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -7313,6 +7313,10 @@ CreateCheckPoint(int flags)
 	if (PriorRedoPtr != InvalidXLogRecPtr)
 		UpdateCheckPointDistanceEstimate(RedoRecPtr - PriorRedoPtr);
 
+#ifdef USE_INJECTION_POINTS
+	INJECTION_POINT("checkpoint-before-old-wal-removal");
+#endif
+
 	/*
 	 * Delete old log files, those no longer needed for last checkpoint to
 	 * prevent the disk holding the xlog from growing full.
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index 4407df84a1c..206fb932484 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -29,6 +29,7 @@
 #include "postgres.h"
 
 #include "access/xact.h"
+#include "access/xlog_internal.h"
 #include "access/xlogutils.h"
 #include "fmgr.h"
 #include "miscadmin.h"
@@ -41,6 +42,7 @@
 #include "storage/proc.h"
 #include "storage/procarray.h"
 #include "utils/builtins.h"
+#include "utils/injection_point.h"
 #include "utils/inval.h"
 #include "utils/memutils.h"
 
@@ -1844,9 +1846,13 @@ LogicalConfirmReceivedLocation(XLogRecPtr lsn)
 	{
 		bool		updated_xmin = false;
 		bool		updated_restart = false;
+		XLogRecPtr	restart_lsn pg_attribute_unused();
 
 		SpinLockAcquire(&MyReplicationSlot->mutex);
 
+		/* remember the old restart lsn */
+		restart_lsn = MyReplicationSlot->data.restart_lsn;
+
 		/*
 		 * Prevent moving the confirmed_flush backwards, as this could lead to
 		 * data duplication issues caused by replicating already replicated
@@ -1908,6 +1914,18 @@ LogicalConfirmReceivedLocation(XLogRecPtr lsn)
 		 */
 		if (updated_xmin || updated_restart)
 		{
+#ifdef USE_INJECTION_POINTS
+			XLogSegNo	seg1,
+						seg2;
+
+			XLByteToSeg(restart_lsn, seg1, wal_segment_size);
+			XLByteToSeg(MyReplicationSlot->data.restart_lsn, seg2, wal_segment_size);
+
+			/* trigger injection point, but only if segment changes */
+			if (seg1 != seg2)
+				INJECTION_POINT("logical-replication-slot-advance-segment");
+#endif
+
 			ReplicationSlotMarkDirty();
 			ReplicationSlotSave();
 			elog(DEBUG1, "updated xmin: %u restart: %u", updated_xmin, updated_restart);