From eef5f02a5c22ccc520c20623d70eaf093a039f09 Mon Sep 17 00:00:00 2001
From: Tomas Vondra <tomas@vondra.me>
Date: Thu, 21 Nov 2024 20:37:00 +0100
Subject: [PATCH 1/2] injection points

---
 src/backend/access/transam/xlog.c         |  4 ++++
 src/backend/replication/logical/logical.c | 18 ++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 6f58412bcab..8f9629866c3 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -7310,6 +7310,10 @@ 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 e941bb491d8..569c1925ecc 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -30,6 +30,7 @@
 
 #include "access/xact.h"
 #include "access/xlogutils.h"
+#include "access/xlog_internal.h"
 #include "fmgr.h"
 #include "miscadmin.h"
 #include "pgstat.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;
 
 		SpinLockAcquire(&MyReplicationSlot->mutex);
 
+		/* remember the old restart lsn */
+		restart_lsn = MyReplicationSlot->data.restart_lsn;
+
 		MyReplicationSlot->data.confirmed_flush = lsn;
 
 		/* if we're past the location required for bumping xmin, do so */
@@ -1888,6 +1894,18 @@ LogicalConfirmReceivedLocation(XLogRecPtr lsn)
 		/* first write new xmin to disk, so we know what's up after a crash */
 		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);
-- 
2.47.0