Subject: [PATCH] Make End-Of-Recovery error less scary

From: Kyotaro Horiguchi <[email-masked]>
Date: Fri, 28 Feb 2020 15:52:58 +0900

When recovery in any type ends, we see a bit scary error message like
"invalid record length" that suggests something serious is happening.
Make this message less scary as "reached end of WAL".
---
 src/backend/access/transam/xlog.c | 45 ++++++++++++++++++++++++++-----
 1 file changed, 38 insertions(+), 7 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index d19408b3be..452c376f62 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -4288,6 +4288,10 @@ ReadRecord(XLogReaderState *xlogreader, int emode,
 		EndRecPtr = xlogreader->EndRecPtr;
 		if (record == NULL)
 		{
+			int actual_emode =
+				emode_for_corrupt_record(emode,
+										 ReadRecPtr ? ReadRecPtr : EndRecPtr);
+
 			if (readFile >= 0)
 			{
 				close(readFile);
@@ -4295,14 +4299,41 @@ ReadRecord(XLogReaderState *xlogreader, int emode,
 			}
 
 			/*
-			 * We only end up here without a message when XLogPageRead()
-			 * failed - in that case we already logged something. In
-			 * StandbyMode that only happens if we have been triggered, so we
-			 * shouldn't loop anymore in that case.
+			 * randAccess here means we are reading successive records during
+			 * recovery. If we get here during recovery, we can assume that we
+			 * reached the end of WAL.  Otherwise something's really wrong and
+			 * we report just only the errormsg if any. If we don't receive
+			 * errormsg here, we already logged something.  We don't emit
+			 * "reached end of WAL" in muted messages.
+			 *
+			 * Note: errormsg is alreay translated.
 			 */
-			if (errormsg)
-				ereport(emode_for_corrupt_record(emode, EndRecPtr),
-						(errmsg_internal("%s", errormsg) /* already translated */ ));
+			if (!private->randAccess && actual_emode == emode)
+			{
+				if (StandbyMode)
+					ereport(actual_emode,
+							(errmsg ("rached end of WAL at %X/%X on timeline %u in %s during streaming replication",
+									 (uint32) (EndRecPtr >> 32), (uint32) EndRecPtr,
+									 ThisTimeLineID,
+									 xlogSourceNames[currentSource]),
+							 (errormsg ? errdetail_internal("%s", errormsg) : 0)));
+				else if (InArchiveRecovery)
+					ereport(actual_emode,
+							(errmsg ("rached end of WAL at %X/%X on timeline %u in %s during archive recovery",
+									 (uint32) (EndRecPtr >> 32), (uint32) EndRecPtr,
+									 ThisTimeLineID,
+									 xlogSourceNames[currentSource]),
+							 (errormsg ? errdetail_internal("%s", errormsg) : 0)));
+				else
+					ereport(actual_emode,
+							(errmsg ("rached end of WAL at %X/%X on timeline %u in %s during crash recovery",
+									 (uint32) (EndRecPtr >> 32), (uint32) EndRecPtr,
+									 ThisTimeLineID,
+									 xlogSourceNames[currentSource]),
+							 (errormsg ? errdetail_internal("%s", errormsg) : 0)));
+			}
+			else if (errormsg)
+				ereport(actual_emode, (errmsg_internal("%s", errormsg)));
 		}
 
 		/*
-- 
2.18.2

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