From e0025875ecf81ce4b84986147b023822eb14a4ee Mon Sep 17 00:00:00 2001
From: Duong Nguyen <duongnt.is@gmail.com>
Date: Fri, 24 May 2024 13:08:55 -0700
Subject: [PATCH] RATIS-2093. Decouple metadata and configuration entries from
 appendEntries buffer for stateMachineCache' (#1096)

---
 .../server/raftlog/segmented/SegmentedRaftLog.java | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/ratis-server/src/main/java/org/apache/ratis/server/raftlog/segmented/SegmentedRaftLog.java b/ratis-server/src/main/java/org/apache/ratis/server/raftlog/segmented/SegmentedRaftLog.java
index 7c33adf00a..27b771ff1a 100644
--- a/ratis-server/src/main/java/org/apache/ratis/server/raftlog/segmented/SegmentedRaftLog.java
+++ b/ratis-server/src/main/java/org/apache/ratis/server/raftlog/segmented/SegmentedRaftLog.java
@@ -456,13 +456,17 @@ protected CompletableFuture<Long> appendEntryImpl(ReferenceCountedObject<LogEntr
       // to statemachine first and then to the cache. Not following the order
       // will leave a spurious entry in the cache.
       final Task write = fileLogWorker.writeLogEntry(entryRef, removedStateMachineData, context);
-      if (stateMachineCachingEnabled && (removedStateMachineData != entry)) {
+      if (stateMachineCachingEnabled) {
         // The stateMachineData will be cached inside the StateMachine itself.
-        cache.appendEntry(LogSegment.Op.WRITE_CACHE_WITH_STATE_MACHINE_CACHE,
-            ReferenceCountedObject.wrap(removedStateMachineData));
+        if (removedStateMachineData != entry) {
+          cache.appendEntry(LogSegment.Op.WRITE_CACHE_WITH_STATE_MACHINE_CACHE,
+              ReferenceCountedObject.wrap(removedStateMachineData));
+        } else {
+          cache.appendEntry(LogSegment.Op.WRITE_CACHE_WITH_STATE_MACHINE_CACHE,
+              ReferenceCountedObject.wrap(LogProtoUtils.copy(removedStateMachineData)));
+        }
       } else {
-        cache.appendEntry(LogSegment.Op.WRITE_CACHE_WITHOUT_STATE_MACHINE_CACHE, entryRef
-        );
+        cache.appendEntry(LogSegment.Op.WRITE_CACHE_WITHOUT_STATE_MACHINE_CACHE, entryRef);
       }
       return write.getFuture().whenComplete((clientReply, exception) -> appendEntryTimerContext.stop());
     } catch (Exception e) {