1 files changed, 38 insertions, 8 deletions
diff --git a/workhorse/internal/gitaly/gitaly.go b/workhorse/internal/gitaly/gitaly.go
index 6ea99962056..362f380dc4d 100644
--- a/workhorse/internal/gitaly/gitaly.go
+++ b/workhorse/internal/gitaly/gitaly.go
@@ -11,6 +11,7 @@ import (
 	grpc_prometheus "github.com/grpc-ecosystem/go-grpc-prometheus"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/sirupsen/logrus"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/metadata"
 
@@ -23,15 +24,19 @@ import (
 )
 
 type Server struct {
-	Address  string            `json:"address"`
-	Token    string            `json:"token"`
-	Features map[string]string `json:"features"`
+	Address     string            `json:"address"`
+	Token       string            `json:"token"`
+	Features    map[string]string `json:"features"`
+	Sidechannel bool              `json:"sidechannel"`
 }
 
-type cacheKey struct{ address, token string }
+type cacheKey struct {
+	address, token string
+	sidechannel    bool
+}
 
 func (server Server) cacheKey() cacheKey {
-	return cacheKey{address: server.Address, token: server.Token}
+	return cacheKey{address: server.Address, token: server.Token, sidechannel: server.Sidechannel}
 }
 
 type connectionsCache struct {
@@ -41,9 +46,17 @@ type connectionsCache struct {
 
 var (
 	jsonUnMarshaler = jsonpb.Unmarshaler{AllowUnknownFields: true}
-	cache           = connectionsCache{
+	// This connection cache map contains two types of connections:
+	// - Normal gRPC connections
+	// - Sidechannel connections. When client dials to the Gitaly server, the
+	// server multiplexes the connection using Yamux. In the future, the server
+	// can open another stream to transfer data without gRPC. Besides, we apply
+	// a framing protocol to add the half-close capability to Yamux streams.
+	// Hence, we cannot use those connections interchangeably.
+	cache = connectionsCache{
 		connections: make(map[cacheKey]*grpc.ClientConn),
 	}
+	sidechannelRegistry *gitalyclient.SidechannelRegistry
 
 	connectionsTotal = promauto.NewCounterVec(
 		prometheus.CounterOpts{
@@ -54,6 +67,12 @@ var (
 	)
 )
 
+func InitializeSidechannelRegistry(logger *logrus.Logger) {
+	if sidechannelRegistry == nil {
+		sidechannelRegistry = gitalyclient.NewSidechannelRegistry(logrus.NewEntry(logger))
+	}
+}
+
 func withOutgoingMetadata(ctx context.Context, features map[string]string) context.Context {
 	md := metadata.New(nil)
 	for k, v := range features {
@@ -72,7 +91,12 @@ func NewSmartHTTPClient(ctx context.Context, server Server) (context.Context, *S
 		return nil, nil, err
 	}
 	grpcClient := gitalypb.NewSmartHTTPServiceClient(conn)
-	return withOutgoingMetadata(ctx, server.Features), &SmartHTTPClient{grpcClient}, nil
+	smartHTTPClient := &SmartHTTPClient{
+		SmartHTTPServiceClient: grpcClient,
+		sidechannelRegistry:    sidechannelRegistry,
+		useSidechannel:         server.Sidechannel,
+	}
+	return withOutgoingMetadata(ctx, server.Features), smartHTTPClient, nil
 }
 
 func NewBlobClient(ctx context.Context, server Server) (context.Context, *BlobClient, error) {
@@ -173,7 +197,13 @@ func newConnection(server Server) (*grpc.ClientConn, error) {
 		),
 	)
 
-	conn, connErr := gitalyclient.Dial(server.Address, connOpts)
+	var conn *grpc.ClientConn
+	var connErr error
+	if server.Sidechannel {
+		conn, connErr = gitalyclient.DialSidechannel(context.Background(), server.Address, sidechannelRegistry, connOpts) // lint:allow context.Background
+	} else {
+		conn, connErr = gitalyclient.Dial(server.Address, connOpts)
+	}
 
 	label := "ok"
 	if connErr != nil {