raft: fix memoryStorage append

raft/log.go

@@ -81,7 +81,7 @@ func (l *raftLog) maybeAppend(index, logTerm, committed uint64, ents ...pb.Entry
 		switch {
 		case ci == 0:
 		case ci <= l.committed:
-			panic("conflict with committed entry")
+			log.Panicf("conflict(%d) with committed entry [committed(%d)]", ci, l.committed)
 		default:
 			l.append(ci-1, ents[ci-from:]...)
 		}

raft/storage.go

@@ -176,5 +176,12 @@ func (ms *MemoryStorage) Compact(i uint64, cs *pb.ConfState, data []byte) error
 func (ms *MemoryStorage) Append(entries []pb.Entry) {
 	ms.Lock()
 	defer ms.Unlock()
+	if len(entries) == 0 {
+		return
+	}
+	offset := entries[0].Index - ms.snapshot.Metadata.Index
+	if uint64(len(ms.ents)) >= offset {
+		ms.ents = ms.ents[:offset]
+	}
 	ms.ents = append(ms.ents, entries...)
 }