fix(replication): fix wrong memory status block replication (#569)

### Motivation

The follower didn't update the `lastAppendedOffset` status when the
leader truncated the follower, which caused some expected entries to be
filtered by deduplication logic and never recovered.

The server will keep printing:

```
{"level":"warn","time":"2024-11-13T11:38:33.0884113Z","component":"follower-cursor","error":{"error":"rpc error: code = Unknown desc = 20874694 can not immediately follow 20874678: oxia: invalid next offset in wal","kind":"*status.Error","stack":null},"follower":"xxxxxx","namespace":"xxxxxxxx","shard":13,"term":307,"time":"2024-11-13T11:38:33.088438126Z","message":"Error while receiving acks"}
```

### Modification

- Align `lastAppendedOffset` alone with internal WAL headOffset.

server/follower_controller.go

@@ -337,6 +337,7 @@ func (fc *followerController) Truncate(req *proto.TruncateRequest) (*proto.Trunc
 		return nil, errors.Wrapf(err, "failed to truncate wal. truncate-offset: %d - wal-last-offset: %d",
 			req.HeadEntryId.Offset, fc.wal.LastOffset())
 	}
+	fc.lastAppendedOffset = headOffset
 
 	return &proto.TruncateResponse{
 		HeadEntryId: &proto.EntryId{

server/follower_controller_test.go

@@ -87,8 +87,7 @@ func TestFollower(t *testing.T) {
 	wg := common.NewWaitGroup(1)
 
 	go func() {
-		err := fc.Replicate(stream)
-		assert.ErrorIs(t, err, context.Canceled)
+		_ = fc.Replicate(stream)
 		wg.Done()
 	}()
 
@@ -111,6 +110,56 @@ func TestFollower(t *testing.T) {
 	assert.Equal(t, proto.ServingStatus_FOLLOWER, fc.Status())
 	assert.EqualValues(t, 1, fc.Term())
 
+	// close follower
+	assert.NoError(t, fc.Close())
+
+	// new term to test if we can continue replicate messages
+	fc, err = NewFollowerController(Config{}, common.DefaultNamespace, shardId, walFactory, kvFactory)
+	assert.NoError(t, err)
+	assert.Equal(t, proto.ServingStatus_NOT_MEMBER, fc.Status())
+	_, err = fc.NewTerm(&proto.NewTermRequest{Term: 2})
+	assert.NoError(t, err)
+	assert.Equal(t, proto.ServingStatus_FENCED, fc.Status())
+	assert.EqualValues(t, 2, fc.Term())
+	truncateResp, err = fc.Truncate(&proto.TruncateRequest{
+		Term: 2,
+		HeadEntryId: &proto.EntryId{
+			Term:   1,
+			Offset: 0,
+		},
+	})
+	assert.NoError(t, err)
+	assert.EqualValues(t, 2, truncateResp.HeadEntryId.Term)
+
+	assert.Equal(t, proto.ServingStatus_FOLLOWER, fc.Status())
+	stream = newMockServerReplicateStream()
+	wg = common.NewWaitGroup(1)
+	go func() {
+		err := fc.Replicate(stream)
+		assert.ErrorIs(t, err, context.Canceled)
+		wg.Done()
+	}()
+	stream.AddRequest(createAddRequest(t, 2, 0, map[string]string{"a": "0", "b": "1"}, wal.InvalidOffset))
+	// Wait for response
+	response = stream.GetResponse()
+	assert.Equal(t, proto.ServingStatus_FOLLOWER, fc.Status())
+	assert.EqualValues(t, 0, response.Offset)
+	// Write next entry
+	stream.AddRequest(createAddRequest(t, 2, 1, map[string]string{"a": "4", "b": "5"}, wal.InvalidOffset))
+
+	// Wait for response
+	response = stream.GetResponse()
+	assert.EqualValues(t, 1, response.Offset)
+
+	assert.Equal(t, proto.ServingStatus_FOLLOWER, fc.Status())
+	assert.EqualValues(t, 2, fc.Term())
+
+	stream.AddRequest(createAddRequest(t, 2, 2, map[string]string{"a": "4", "b": "5"}, wal.InvalidOffset))
+	response = stream.GetResponse()
+	assert.EqualValues(t, 2, response.Offset)
+	assert.Equal(t, proto.ServingStatus_FOLLOWER, fc.Status())
+	assert.EqualValues(t, 2, fc.Term())
+
 	// Double-check the values in the DB
 	// Keys are not there because they were not part of the commit offset
 	dbRes, err := fc.(*followerController).db.Get(&proto.GetRequest{