lightning: use gRPC prepared message to avoid duplicated encoding

br/pkg/lightning/backend/local/BUILD.bazel

@@ -167,6 +167,7 @@ go_test(
         "@com_github_tikv_pd_client//errs",
         "@org_golang_google_grpc//:grpc",
         "@org_golang_google_grpc//codes",
+        "@org_golang_google_grpc//encoding",
         "@org_golang_google_grpc//status",
         "@org_uber_go_atomic//:atomic",
     ],

br/pkg/lightning/backend/local/local_test.go

@@ -29,6 +29,7 @@ import (
 	"sync/atomic"
 	"testing"
 	"time"
+	_ "unsafe"
 
 	"github.com/cockroachdb/pebble"
 	"github.com/docker/go-units"
@@ -59,6 +60,7 @@ import (
 	pd "github.com/tikv/pd/client"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/encoding"
 	"google.golang.org/grpc/status"
 )
 
@@ -742,6 +744,33 @@ func (m mockWriteClient) CloseAndRecv() (*sst.WriteResponse, error) {
 	return m.writeResp, nil
 }
 
+type baseCodec interface {
+	Marshal(v interface{}) ([]byte, error)
+	Unmarshal(data []byte, v interface{}) error
+}
+
+//go:linkname newContextWithRPCInfo google.golang.org/grpc.newContextWithRPCInfo
+func newContextWithRPCInfo(ctx context.Context, failfast bool, codec baseCodec, cp grpc.Compressor, comp encoding.Compressor) context.Context
+
+type mockCodec struct{}
+
+func (m mockCodec) Marshal(v interface{}) ([]byte, error) {
+	return nil, nil
+}
+
+func (m mockCodec) Unmarshal(data []byte, v interface{}) error {
+	return nil
+}
+
+func (m mockWriteClient) Context() context.Context {
+	ctx := context.Background()
+	return newContextWithRPCInfo(ctx, false, mockCodec{}, nil, nil)
+}
+
+func (m mockWriteClient) SendMsg(_ interface{}) error {
+	return nil
+}
+
 func (c *mockImportClient) Write(ctx context.Context, opts ...grpc.CallOption) (sst.ImportSST_WriteClient, error) {
 	if c.apiInvokeRecorder != nil {
 		c.apiInvokeRecorder["Write"] = append(c.apiInvokeRecorder["Write"], c.store.GetId())

br/pkg/lightning/backend/local/region_job.go

@@ -39,6 +39,7 @@
 	"github.com/pingcap/tidb/util/codec"
 	"github.com/pingcap/tidb/util/mathutil"
 	"go.uber.org/zap"
+	"google.golang.org/grpc"
 )
 
 type jobStageTp string
@@ -225,7 +226,11 @@
 	leaderID := j.region.Leader.GetId()
 	clients := make([]sst.ImportSST_WriteClient, 0, len(region.GetPeers()))
 	allPeers := make([]*metapb.Peer, 0, len(region.GetPeers()))
-	requests := make([]*sst.WriteRequest, 0, len(region.GetPeers()))
+	req := &sst.WriteRequest{
+		Chunk: &sst.WriteRequest_Meta{
+			Meta: meta,
+		},
+	}
 	for _, peer := range region.GetPeers() {
 		cli, err := clientFactory.Create(ctx, peer.StoreId)
 		if err != nil {
@@ -238,23 +243,17 @@
 		}
 
 		// Bind uuid for this write request
-		req := &sst.WriteRequest{
-			Chunk: &sst.WriteRequest_Meta{
-				Meta: meta,
-			},
-		}
 		if err = wstream.Send(req); err != nil {
 			return annotateErr(err, peer)
 		}
-		req.Chunk = &sst.WriteRequest_Batch{
-			Batch: &sst.WriteBatch{
-				CommitTs: j.engine.TS,
-			},
-		}
 		clients = append(clients, wstream)
-		requests = append(requests, req)
 		allPeers = append(allPeers, peer)
 	}
+	req.Chunk = &sst.WriteRequest_Batch{
+		Batch: &sst.WriteBatch{
+			CommitTs: j.engine.TS,
+		},
+	}
 
 	bytesBuf := bufferPool.NewBuffer()
 	defer bytesBuf.Destroy()
@@ -271,12 +270,19 @@
 	}
 
 	flushKVs := func() error {
+		req.Chunk.(*sst.WriteRequest_Batch).Batch.Pairs = pairs[:count]
+		preparedMsg := &grpc.PreparedMsg{}
+		// by reading the source code, Encode need to find codec and compression from the stream
+		// because all stream has the same codec and compression, we can use any one of them
+		if err := preparedMsg.Encode(clients[0], req); err != nil {
+			return err
+		}
+
 		for i := range clients {
 			if err := writeLimiter.WaitN(ctx, allPeers[i].StoreId, int(size)); err != nil {
 				return errors.Trace(err)
 			}
-			requests[i].Chunk.(*sst.WriteRequest_Batch).Batch.Pairs = pairs[:count]
-			if err := clients[i].Send(requests[i]); err != nil {
+			if err := clients[i].SendMsg(preparedMsg); err != nil {
 				return annotateErr(err, allPeers[i])
 			}
 		}