perf(metarepos): avoid copy overhead by removing unnecessary converti…

…ng from byte slice to string

This change removes copy overhead caused by unnecessary type casting from byte slice to string.
Refer to [this blog](https://www.sobyte.net/post/2022-09/string-byte-convertion/#performance-testing)
for performance.

internal/metarepos/raft.go

@@ -33,7 +33,7 @@ import (
 type raftNode struct {
 	raftConfig
 
-	proposeC    chan string              // proposed messages from app
+	proposeC    chan []byte              // proposed messages from app
 	confChangeC chan raftpb.ConfChange   // proposed cluster config changes
 	commitC     chan *raftCommittedEntry // entries committed to app
 	snapshotC   chan struct{}            // snapshot trigger
@@ -98,7 +98,7 @@ var purgeInterval = 30 * time.Second
 // current), then new log entries.
 func newRaftNode(cfg raftConfig,
 	snapshotGetter SnapshotGetter,
-	proposeC chan string,
+	proposeC chan []byte,
 	confChangeC chan raftpb.ConfChange,
 	tmStub *telemetryStub,
 	logger *zap.Logger) *raftNode {
@@ -707,7 +707,7 @@ Loop:
 
 			// blocks until accepted by raft state machine
 			// TODO:: handle dropped proposal
-			err := rc.node.Propose(context.TODO(), []byte(prop))
+			err := rc.node.Propose(context.TODO(), prop)
 			if err != nil {
 				rc.logger.Warn("proposal fail", zap.String("err", err.Error()))
 			}

internal/metarepos/raft_metadata_repository.go

@@ -64,7 +64,7 @@ type RaftMetadataRepository struct {
 	proposeC      chan *mrpb.RaftEntry
 	commitC       chan *committedEntry
 	rnConfChangeC chan raftpb.ConfChange
-	rnProposeC    chan string
+	rnProposeC    chan []byte
 	rnCommitC     chan *raftCommittedEntry
 
 	// for report
@@ -110,7 +110,7 @@ func NewRaftMetadataRepository(opts ...Option) *RaftMetadataRepository {
 		proposeC:      make(chan *mrpb.RaftEntry, 4096),
 		commitC:       make(chan *committedEntry, 4096),
 		rnConfChangeC: make(chan raftpb.ConfChange, 1),
-		rnProposeC:    make(chan string),
+		rnProposeC:    make(chan []byte),
 		reportQueue:   make([]*mrpb.Report, 0, 1024),
 		runner:        runner.New("mr", cfg.logger),
 		sw:            stopwaiter.New(),
@@ -308,7 +308,7 @@ Loop:
 			}
 
 			select {
-			case mr.rnProposeC <- string(b):
+			case mr.rnProposeC <- b:
 			case <-ctx.Done():
 				mr.sendAck(e.NodeIndex, e.RequestIndex, ctx.Err())
 			}

internal/metarepos/raft_test.go

@@ -26,7 +26,7 @@ type cluster struct {
 	peers       []string
 	peerToIdx   map[uint64]int
 	commitC     []<-chan *raftCommittedEntry
-	proposeC    []chan string
+	proposeC    []chan []byte
 	confChangeC []chan raftpb.ConfChange
 	running     []bool
 	stop        []stopFunc
@@ -49,7 +49,7 @@ func newCluster(n int) *cluster {
 		peers:       peers,
 		peerToIdx:   make(map[uint64]int),
 		commitC:     make([]<-chan *raftCommittedEntry, len(peers)),
-		proposeC:    make([]chan string, len(peers)),
+		proposeC:    make([]chan []byte, len(peers)),
 		confChangeC: make([]chan raftpb.ConfChange, len(peers)),
 		running:     make([]bool, len(peers)),
 		stop:        make([]stopFunc, len(peers)),
@@ -66,7 +66,7 @@ func newCluster(n int) *cluster {
 
 		os.RemoveAll(fmt.Sprintf("raftdata/wal/%d", nodeID))  //nolint:errcheck,revive // TODO:: Handle an error returned.
 		os.RemoveAll(fmt.Sprintf("raftdata/snap/%d", nodeID)) //nolint:errcheck,revive // TODO:: Handle an error returned.
-		clus.proposeC[i] = make(chan string, 1)
+		clus.proposeC[i] = make(chan []byte, 1)
 		clus.confChangeC[i] = make(chan raftpb.ConfChange, 1)
 		//logger, _ := zap.NewDevelopment()
 		logger := zap.NewNop()
@@ -152,7 +152,7 @@ func TestProposeOnFollower(t *testing.T) {
 	donec := make(chan struct{})
 	for i := range clus.peers {
 		// feedback for "n" committed entries, then update donec
-		go func(pC chan<- string, cC <-chan *raftCommittedEntry) {
+		go func(pC chan<- []byte, cC <-chan *raftCommittedEntry) {
 		Loop:
 			for range cC {
 				break Loop
@@ -165,7 +165,7 @@ func TestProposeOnFollower(t *testing.T) {
 		}(clus.proposeC[i], clus.commitC[i])
 
 		// one message feedback per node
-		go func(i int) { clus.proposeC[i] <- fmt.Sprintf("%d", i) }(i)
+		go func(i int) { clus.proposeC[i] <- []byte(fmt.Sprintf("%d", i)) }(i)
 	}
 
 	for range clus.peers {
@@ -187,7 +187,7 @@ func TestFailoverLeaderElection(t *testing.T) {
 			ctx, cancel := context.WithCancel(context.TODO())
 			cancels[i] = cancel
 			// feedback for "n" committed entries, then update donec
-			go func(ctx context.Context, idx int, pC chan<- string, cC <-chan *raftCommittedEntry) {
+			go func(ctx context.Context, _ int, _ chan<- []byte, cC <-chan *raftCommittedEntry) {
 				defer wg.Done()
 
 			Loop: