From 36de193b974eed4c45391af34c36f392a0968166 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 1 Aug 2023 11:49:53 +0900
Subject: [PATCH] Tweak to force OOM behavior when replaying records

---
 src/backend/access/transam/xlogreader.c | 27 ++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index c9f9f6e98f..73006f05b8 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -547,6 +547,7 @@ XLogDecodeNextRecord(XLogReaderState *state, bool nonblocking)
 	int			readOff;
 	DecodedXLogRecord *decoded;
 	char	   *errormsg;		/* not used */
+	bool		trigger_oom = false;
 
 	/*
 	 * randAccess indicates whether to verify the previous-record pointer of
@@ -691,7 +692,31 @@ restart:
 	decoded = XLogReadRecordAlloc(state,
 								  total_len,
 								  !nonblocking /* allow_oversized */ );
-	if (decoded == NULL)
+
+#ifndef FRONTEND
+	/*
+	 * Trick to emulate an OOM after a hardcoded number of records
+	 * replayed.
+	 */
+	{
+		struct stat fstat;
+		static int counter = 0;
+
+		if (stat("/tmp/xlogreader_oom", &fstat) == 0)
+		{
+			counter++;
+			if (counter >= 100)
+			{
+				trigger_oom = true;
+
+				/* Reset counter, to not fail when shutting down WAL */
+				counter = 0;
+			}
+		}
+	}
+#endif
+
+	if (decoded == NULL || trigger_oom)
 	{
 		/*
 		 * There is no space in the decode buffer.  The caller should help
-- 
2.40.1