From 5166201498e5c23fadaf579262cfe8bbb82dd8d6 Mon Sep 17 00:00:00 2001
From: minux <minu.song@linecorp.com>
Date: Wed, 27 Dec 2023 16:05:47 +0900
Subject: [PATCH] Add replication log details to the exception message when
 replaying ZooKeeper log fails. (#900)

Motivation:
Currently, it is challenging to identify the specific replication log that fails during replay.

Modifications:
- Enhanced exception messages by including details of the replication log that encountered failure.

Result:
- You can now easily identify the failing replication log.
---
 .../replication/ZooKeeperCommandExecutor.java | 34 +++++++++++++------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/server/src/main/java/com/linecorp/centraldogma/server/internal/replication/ZooKeeperCommandExecutor.java b/server/src/main/java/com/linecorp/centraldogma/server/internal/replication/ZooKeeperCommandExecutor.java
index d3b082d8ee..366171c9fc 100644
--- a/server/src/main/java/com/linecorp/centraldogma/server/internal/replication/ZooKeeperCommandExecutor.java
+++ b/server/src/main/java/com/linecorp/centraldogma/server/internal/replication/ZooKeeperCommandExecutor.java
@@ -715,11 +715,12 @@ private synchronized void replayLogs(long targetRevision) {
         }
 
         long nextRevision = info.lastReplayedRevision + 1;
-        try {
-            for (;;) {
+        for (;;) {
+            ReplicationLog<?> l = null;
+            try {
                 final Optional<ReplicationLog<?>> log = loadLog(nextRevision, true);
                 if (log.isPresent()) {
-                    final ReplicationLog<?> l = log.get();
+                    l = log.get();
                     final Command<?> command = l.command();
                     final Object expectedResult = l.result();
                     final Object actualResult = delegate.execute(command).get();
@@ -744,15 +745,28 @@ private synchronized void replayLogs(long targetRevision) {
                 } else {
                     nextRevision++;
                 }
-            }
-        } catch (Throwable t) {
-            logger.error("Failed to replay a log at revision {}; entering read-only mode", nextRevision, t);
-            stopLater();
+            } catch (Throwable t) {
+                if (l != null) {
+                    logger.error(
+                            "Failed to replay a log at revision {}; entering read-only mode. replay log: {}",
+                            nextRevision, l, t);
+                } else {
+                    logger.error("Failed to replay a log at revision {}; entering read-only mode.",
+                                 nextRevision, t);
+                }
+
+                stopLater();
 
-            if (t instanceof ReplicationException) {
-                throw (ReplicationException) t;
+                if (t instanceof ReplicationException) {
+                    throw (ReplicationException) t;
+                }
+                final StringBuilder sb = new StringBuilder();
+                sb.append("failed to replay a log at revision " + nextRevision);
+                if (l != null) {
+                    sb.append(". replay log: ").append(l);
+                }
+                throw new ReplicationException(sb.toString(), t);
             }
-            throw new ReplicationException("failed to replay a log at revision " + nextRevision, t);
         }
     }