Allow setting grpc send and recv message sizes independently

Signed-off-by: Henry Robinson <hrobinson@slack-corp.com>

go/vt/grpcclient/client.go

@@ -110,11 +110,12 @@ func Dial(target string, failFast FailFast, opts ...grpc.DialOption) (*grpc.Clie
 // what that should be.
 func DialContext(ctx context.Context, target string, failFast FailFast, opts ...grpc.DialOption) (*grpc.ClientConn, error) {
 	grpccommon.EnableTracingOpt()
-	msgSize := grpccommon.MaxMessageSize()
+	maxSendSize := grpccommon.MaxMessageSendSize()
+	maxRecvSize := grpccommon.MaxMessageRecvSize()
 	newopts := []grpc.DialOption{
 		grpc.WithDefaultCallOptions(
-			grpc.MaxCallRecvMsgSize(msgSize),
-			grpc.MaxCallSendMsgSize(msgSize),
+			grpc.MaxCallRecvMsgSize(maxRecvSize),
+			grpc.MaxCallSendMsgSize(maxSendSize),
 			grpc.WaitForReady(bool(!failFast)),
 		),
 	}

go/vt/grpccommon/options.go

@@ -30,6 +30,8 @@ var (
 	// accept. Larger messages will be rejected.
 	// Note: We're using 16 MiB as default value because that's the default in MySQL
 	maxMessageSize = 16 * 1024 * 1024
+	maxMsgRecvSize = 0
+	maxMsgSendSize = 0
 	// enableTracing sets a flag to enable grpc client/server tracing.
 	enableTracing bool
 	// enablePrometheus sets a flag to enable grpc client/server grpc monitoring.
@@ -43,6 +45,8 @@ var (
 // command-line arguments.
 func RegisterFlags(fs *pflag.FlagSet) {
 	fs.IntVar(&maxMessageSize, "grpc_max_message_size", maxMessageSize, "Maximum allowed RPC message size. Larger messages will be rejected by gRPC with the error 'exceeding the max size'.")
+	fs.IntVar(&maxMsgSendSize, "grpc_max_message_send_size", maxMsgSendSize, "")
+	fs.IntVar(&maxMsgRecvSize, "grpc_max_message_recv_size", maxMsgRecvSize, "")
 	fs.BoolVar(&enableTracing, "grpc_enable_tracing", enableTracing, "Enable gRPC tracing.")
 	fs.BoolVar(&enablePrometheus, "grpc_prometheus", enablePrometheus, "Enable gRPC monitoring with Prometheus.")
 }
@@ -70,6 +74,20 @@ func MaxMessageSize() int {
 	return maxMessageSize
 }
 
+func MaxMessageRecvSize() int {
+	if maxMsgRecvSize > 0 {
+		return maxMsgRecvSize
+	}
+	return MaxMessageSize()
+}
+
+func MaxMessageSendSize() int {
+	if maxMsgSendSize > 0 {
+		return maxMsgSendSize
+	}
+	return MaxMessageSize()
+}
+
 func init() {
 	stats.NewString("GrpcVersion").Set(grpc.Version)
 }

go/vt/servenv/grpc_server.go

@@ -207,10 +207,12 @@ func createGRPCServer() {
 	// grpc: received message length XXXXXXX exceeding the max size 4194304
 	// Note: For gRPC 1.0.0 it's sufficient to set the limit on the server only
 	// because it's not enforced on the client side.
-	msgSize := grpccommon.MaxMessageSize()
-	log.Infof("Setting grpc max message size to %d", msgSize)
-	opts = append(opts, grpc.MaxRecvMsgSize(msgSize))
-	opts = append(opts, grpc.MaxSendMsgSize(msgSize))
+
+	maxSendSize := grpccommon.MaxMessageSendSize()
+	maxRecvSize := grpccommon.MaxMessageRecvSize()
+	log.Infof("Setting grpc server max message sizes to %d (sending), %d (receiving)", maxSendSize, maxRecvSize)
+	opts = append(opts, grpc.MaxRecvMsgSize(maxRecvSize))
+	opts = append(opts, grpc.MaxSendMsgSize(maxSendSize))
 
 	if gRPCInitialConnWindowSize != 0 {
 		log.Infof("Setting grpc server initial conn window size to %d", int32(gRPCInitialConnWindowSize))