Merge branch...

Merge branch 'qmnguyen0711/1220-implement-postuploadpackwithsidechannel-client-in-workhorse' into 'master'

Implement PostUploadPackWithSidechannel client in Workhorse

See merge request gitlab-org/gitlab!71047

config/feature_flags/development/workhorse_use_sidechannel.yml

+---
+name: workhorse_use_sidechannel
+introduced_by_url:
+rollout_issue_url: https://gitlab.com/gitlab-com/gl-infra/scalability/-/issues/1193
+milestone: '14.4'
+type: development
+group: 'group::scalability'
+default_enabled: false

lib/gitlab/workhorse.rb

@@ -32,7 +32,8 @@ module Gitlab
           GitalyServer: {
             address: Gitlab::GitalyClient.address(repository.storage),
             token: Gitlab::GitalyClient.token(repository.storage),
-            features: Feature::Gitaly.server_feature_flags(repository.project)
+            features: Feature::Gitaly.server_feature_flags(repository.project),
+            sidechannel: Feature.enabled?(:workhorse_use_sidechannel, repository.project, default_enabled: :yaml)
           }
         }
 

spec/lib/gitlab/workhorse_spec.rb

@@ -244,13 +244,15 @@ RSpec.describe Gitlab::Workhorse do
           GitalyServer: {
             features: { 'gitaly-feature-enforce-requests-limits' => 'true' },
             address: Gitlab::GitalyClient.address('default'),
-            token: Gitlab::GitalyClient.token('default')
+            token: Gitlab::GitalyClient.token('default'),
+            sidechannel: false
           }
         }
       end
 
       before do
         allow(Gitlab.config.gitaly).to receive(:enabled).and_return(true)
+        stub_feature_flags(workhorse_use_sidechannel: false)
       end
 
       it 'includes a Repository param' do
@@ -332,6 +334,46 @@ RSpec.describe Gitlab::Workhorse do
 
         it { expect { subject }.to raise_exception('Unsupported action: download') }
       end
+
+      context 'when workhorse_use_sidechannel flag is set' do
+        context 'when a feature flag is set globally' do
+          before do
+            stub_feature_flags(workhorse_use_sidechannel: true)
+          end
+
+          it 'sets the flag to true' do
+            response = described_class.git_http_ok(repository, Gitlab::GlRepository::PROJECT, user, action)
+
+            expect(response.dig(:GitalyServer, :sidechannel)).to eq(true)
+          end
+        end
+
+        context 'when a feature flag is set for a single project' do
+          before do
+            stub_feature_flags(workhorse_use_sidechannel: project)
+          end
+
+          it 'sets the flag to true for that project' do
+            response = described_class.git_http_ok(repository, Gitlab::GlRepository::PROJECT, user, action)
+
+            expect(response.dig(:GitalyServer, :sidechannel)).to eq(true)
+          end
+
+          it 'sets the flag to false for other projects' do
+            other_project = create(:project, :public, :repository)
+            response = described_class.git_http_ok(other_project.repository, Gitlab::GlRepository::PROJECT, user, action)
+
+            expect(response.dig(:GitalyServer, :sidechannel)).to eq(false)
+          end
+
+          it 'sets the flag to false when there is no project' do
+            snippet = create(:personal_snippet, :repository)
+            response = described_class.git_http_ok(snippet.repository, Gitlab::GlRepository::SNIPPET, user, action)
+
+            expect(response.dig(:GitalyServer, :sidechannel)).to eq(false)
+          end
+        end
+      end
     end
 
     context 'when receive_max_input_size has been updated' do

workhorse/gitaly_integration_test.go

@@ -230,7 +230,7 @@ func TestAllowedGetGitArchiveOldPayload(t *testing.T) {
 
 	// Create the repository in the Gitaly server
 	apiResponse := realGitalyOkBody(t)
-	repo := apiResponse.Repository
+	repo := &apiResponse.Repository
 	require.NoError(t, ensureGitalyRepository(t, apiResponse))
 
 	archivePath := path.Join(scratchDir, "my/path")

workhorse/gitaly_test.go

@@ -5,6 +5,7 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"math/rand"
 	"net"
@@ -20,12 +21,16 @@ import (
 
 	"github.com/golang/protobuf/jsonpb" //lint:ignore SA1019 https://gitlab.com/gitlab-org/gitlab/-/issues/324868
 	"github.com/golang/protobuf/proto"  //lint:ignore SA1019 https://gitlab.com/gitlab-org/gitlab/-/issues/324868
+	"github.com/sirupsen/logrus"
 	"github.com/stretchr/testify/require"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials/insecure"
 
 	"gitlab.com/gitlab-org/gitaly/v14/proto/go/gitalypb"
 
+	gitalyclient "gitlab.com/gitlab-org/gitaly/v14/client"
+
 	"gitlab.com/gitlab-org/gitlab/workhorse/internal/api"
 	"gitlab.com/gitlab-org/gitlab/workhorse/internal/git"
 	"gitlab.com/gitlab-org/gitlab/workhorse/internal/gitaly"
@@ -375,12 +380,24 @@ func TestPostReceivePackRouting(t *testing.T) {
 	}
 }
 
+type gitalyServerStarter func(*testing.T, codes.Code) (*combinedServer, string)
+
 // ReaderFunc is an adapter to turn a conforming function into an io.Reader.
 type ReaderFunc func(b []byte) (int, error)
 
 func (r ReaderFunc) Read(b []byte) (int, error) { return r(b) }
 
 func TestPostUploadPackProxiedToGitalySuccessfully(t *testing.T) {
+	testPostUploadPackProxiedToGitalySuccessfully(t, startGitalyServer, gitOkBody(t))
+}
+
+func TestPostUploadPackWithSidechannelProxiedToGitalySuccessfully(t *testing.T) {
+	testPostUploadPackProxiedToGitalySuccessfully(
+		t, startGitalyServerWithSideChannel(testhelper.PostUploadPackWithSidechannel), gitOkBodyWithSidechannel(t),
+	)
+}
+
+func testPostUploadPackProxiedToGitalySuccessfully(t *testing.T, startGitaly gitalyServerStarter, apiResponse *api.Response) {
 	for i, tc := range []struct {
 		showAllRefs bool
 		code        codes.Code
@@ -391,10 +408,9 @@ func TestPostUploadPackProxiedToGitalySuccessfully(t *testing.T) {
 		{false, codes.Unavailable},
 	} {
 		t.Run(fmt.Sprintf("Case %d", i), func(t *testing.T) {
-			apiResponse := gitOkBody(t)
 			apiResponse.ShowAllRefs = tc.showAllRefs
 
-			gitalyServer, socketPath := startGitalyServer(t, tc.code)
+			gitalyServer, socketPath := startGitaly(t, tc.code)
 			defer gitalyServer.GracefulStop()
 
 			apiResponse.GitalyServer.Address = "unix:" + socketPath
@@ -460,8 +476,16 @@ func TestPostUploadPackProxiedToGitalySuccessfully(t *testing.T) {
 
 func TestPostUploadPackProxiedToGitalyInterrupted(t *testing.T) {
 	apiResponse := gitOkBody(t)
+	testPostUploadPackProxiedToGitalyInterrupted(t, startGitalyServer, apiResponse)
+}
 
-	gitalyServer, socketPath := startGitalyServer(t, codes.OK)
+func TestPostUploadPackWithSidechannelProxiedToGitalyInterrupted(t *testing.T) {
+	apiResponse := gitOkBodyWithSidechannel(t)
+	testPostUploadPackProxiedToGitalyInterrupted(t, startGitalyServerWithSideChannel(testhelper.PostUploadPackWithSidechannel), apiResponse)
+}
+
+func testPostUploadPackProxiedToGitalyInterrupted(t *testing.T, startGitaly gitalyServerStarter, apiResponse *api.Response) {
+	gitalyServer, socketPath := startGitaly(t, codes.OK)
 	defer gitalyServer.GracefulStop()
 
 	apiResponse.GitalyServer.Address = "unix:" + socketPath
@@ -493,10 +517,19 @@ func TestPostUploadPackProxiedToGitalyInterrupted(t *testing.T) {
 }
 
 func TestPostUploadPackRouting(t *testing.T) {
-	gitalyServer, socketPath := startGitalyServer(t, codes.OK)
+	apiResponse := gitOkBody(t)
+	testPostUploadPackRouting(t, startGitalyServer, apiResponse)
+}
+
+func TestPostUploadPackWithSidechannelRouting(t *testing.T) {
+	apiResponse := gitOkBodyWithSidechannel(t)
+	testPostUploadPackRouting(t, startGitalyServerWithSideChannel(testhelper.PostUploadPackWithSidechannel), apiResponse)
+}
+
+func testPostUploadPackRouting(t *testing.T, startGitaly gitalyServerStarter, apiResponse *api.Response) {
+	gitalyServer, socketPath := startGitaly(t, codes.OK)
 	defer gitalyServer.GracefulStop()
 
-	apiResponse := gitOkBody(t)
 	apiResponse.GitalyServer.Address = "unix:" + socketPath
 	ts := testAuthServer(t, nil, nil, 200, apiResponse)
 	defer ts.Close()
@@ -869,3 +902,21 @@ func startGitalyServer(t *testing.T, finalMessageCode codes.Code) (*combinedServ
 
 	return &combinedServer{Server: server, GitalyTestServer: gitalyServer}, socketPath
 }
+
+func startGitalyServerWithSideChannel(handler func(interface{}, grpc.ServerStream, io.ReadWriteCloser) error) gitalyServerStarter {
+	return func(t *testing.T, finalMessageCode codes.Code) (*combinedServer, string) {
+		socketPath := path.Join(scratchDir, fmt.Sprintf("gitaly-%d.sock", rand.Int()))
+		if err := os.Remove(socketPath); err != nil && !os.IsNotExist(err) {
+			t.Fatal(err)
+		}
+		server := grpc.NewServer(gitalyclient.TestSidechannelServer(logrus.NewEntry(logrus.StandardLogger()), insecure.NewCredentials(), handler)...)
+		listener, err := net.Listen("unix", socketPath)
+		require.NoError(t, err)
+
+		gitalyServer := testhelper.NewGitalyServer(finalMessageCode)
+
+		go server.Serve(listener)
+
+		return &combinedServer{Server: server, GitalyTestServer: gitalyServer}, socketPath
+	}
+}

workhorse/go.mod

@@ -3,11 +3,11 @@ module gitlab.com/gitlab-org/gitlab/workhorse
 go 1.16
 
 require (
-	github.com/Azure/azure-storage-blob-go v0.11.1-0.20201209121048-6df5d9af221d
+	github.com/Azure/azure-storage-blob-go v0.13.0
 	github.com/BurntSushi/toml v0.3.1
 	github.com/FZambia/sentinel v1.0.0
 	github.com/alecthomas/chroma v0.7.3
-	github.com/aws/aws-sdk-go v1.37.0
+	github.com/aws/aws-sdk-go v1.38.35
 	github.com/certifi/gocertifi v0.0.0-20200922220541-2c3bb06c6054 // indirect
 	github.com/disintegration/imaging v1.6.2
 	github.com/getsentry/raven-go v0.2.0
@@ -28,14 +28,14 @@ require (
 	github.com/sirupsen/logrus v1.8.1
 	github.com/smartystreets/goconvey v1.6.4
 	github.com/stretchr/testify v1.7.0
-	gitlab.com/gitlab-org/gitaly/v14 v14.0.0-rc1
+	gitlab.com/gitlab-org/gitaly/v14 v14.3.0-rc2.0.20211007055622-df7dadcc3f74
 	gitlab.com/gitlab-org/labkit v1.6.0
-	gocloud.dev v0.21.1-0.20201223184910-5094f54ed8bb
+	gocloud.dev v0.23.0
 	golang.org/x/image v0.0.0-20191009234506-e7c1f5e7dbb8
 	golang.org/x/lint v0.0.0-20201208152925-83fdc39ff7b5
-	golang.org/x/net v0.0.0-20210316092652-d523dce5a7f4
+	golang.org/x/net v0.0.0-20210505214959-0714010a04ed
 	golang.org/x/tools v0.1.0
-	google.golang.org/grpc v1.37.0
+	google.golang.org/grpc v1.38.0
 	gopkg.in/DataDog/dd-trace-go.v1 v1.31.0 // indirect
 	honnef.co/go/tools v0.1.3
 )

workhorse/internal/artifacts/artifacts_store_test.go

@@ -102,11 +102,11 @@ func TestUploadHandlerSendingToExternalStorage(t *testing.T) {
 
 	tests := []struct {
 		name    string
-		preauth api.Response
+		preauth *api.Response
 	}{
 		{
 			name: "ObjectStore Upload",
-			preauth: api.Response{
+			preauth: &api.Response{
 				RemoteObject: api.RemoteObject{
 					StoreURL: storeServer.URL + "/url/put" + qs,
 					ID:       "store-id",
@@ -145,7 +145,7 @@ func TestUploadHandlerSendingToExternalStorageAndStorageServerUnreachable(t *tes
 		t.Fatal("it should not be called")
 	}
 
-	authResponse := api.Response{
+	authResponse := &api.Response{
 		TempPath: tempPath,
 		RemoteObject: api.RemoteObject{
 			StoreURL: "http://localhost:12323/invalid/url",
@@ -171,7 +171,7 @@ func TestUploadHandlerSendingToExternalStorageAndInvalidURLIsUsed(t *testing.T)
 		t.Fatal("it should not be called")
 	}
 
-	authResponse := api.Response{
+	authResponse := &api.Response{
 		TempPath: tempPath,
 		RemoteObject: api.RemoteObject{
 			StoreURL: "htt:////invalid-url",
@@ -203,7 +203,7 @@ func TestUploadHandlerSendingToExternalStorageAndItReturnsAnError(t *testing.T)
 	storeServer := httptest.NewServer(storeServerMux)
 	defer storeServer.Close()
 
-	authResponse := api.Response{
+	authResponse := &api.Response{
 		RemoteObject: api.RemoteObject{
 			StoreURL: storeServer.URL + "/url/put",
 			ID:       "store-id",
@@ -236,7 +236,7 @@ func TestUploadHandlerSendingToExternalStorageAndSupportRequestTimeout(t *testin
 	storeServer := httptest.NewServer(storeServerMux)
 	defer storeServer.Close()
 
-	authResponse := api.Response{
+	authResponse := &api.Response{
 		RemoteObject: api.RemoteObject{
 			StoreURL: storeServer.URL + "/url/put",
 			ID:       "store-id",
@@ -262,7 +262,7 @@ func TestUploadHandlerMultipartUploadSizeLimit(t *testing.T) {
 	objectURL := server.URL + test.ObjectPath
 
 	uploadSize := 10
-	preauth := api.Response{
+	preauth := &api.Response{
 		RemoteObject: api.RemoteObject{
 			ID: "store-id",
 			MultipartUpload: &api.MultipartUploadParams{
@@ -304,7 +304,7 @@ func TestUploadHandlerMultipartUploadMaximumSizeFromApi(t *testing.T) {
 
 	uploadSize := int64(10)
 	maxSize := uploadSize - 1
-	preauth := api.Response{
+	preauth := &api.Response{
 		MaximumSize: maxSize,
 		RemoteObject: api.RemoteObject{
 			ID: "store-id",

workhorse/internal/artifacts/artifacts_upload_test.go

@@ -35,7 +35,7 @@ const (
 	Path                  = "/url/path"
 )
 
-func testArtifactsUploadServer(t *testing.T, authResponse api.Response, bodyProcessor func(w http.ResponseWriter, r *http.Request)) *httptest.Server {
+func testArtifactsUploadServer(t *testing.T, authResponse *api.Response, bodyProcessor func(w http.ResponseWriter, r *http.Request)) *httptest.Server {
 	mux := http.NewServeMux()
 	mux.HandleFunc(Path+"/authorize", func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != "POST" {
@@ -51,7 +51,7 @@ func testArtifactsUploadServer(t *testing.T, authResponse api.Response, bodyProc
 		w.Write(data)
 	})
 	mux.HandleFunc(Path, func(w http.ResponseWriter, r *http.Request) {
-		opts, err := filestore.GetOpts(&authResponse)
+		opts, err := filestore.GetOpts(authResponse)
 		require.NoError(t, err)
 
 		if r.Method != "POST" {
@@ -128,7 +128,7 @@ func setupWithTmpPath(t *testing.T, filename string, includeFormat bool, format
 		authResponse = &api.Response{TempPath: tempPath}
 	}
 
-	ts := testArtifactsUploadServer(t, *authResponse, bodyProcessor)
+	ts := testArtifactsUploadServer(t, authResponse, bodyProcessor)
 
 	var buffer bytes.Buffer
 	writer := multipart.NewWriter(&buffer)

workhorse/internal/filestore/save_file_opts_test.go

@@ -141,21 +141,21 @@ func TestGetOpts(t *testing.T) {
 func TestGetOptsFail(t *testing.T) {
 	testCases := []struct {
 		desc string
-		in   api.Response
+		in   *api.Response
 	}{
 		{
 			desc: "neither local nor remote",
-			in:   api.Response{},
+			in:   &api.Response{},
 		},
 		{
 			desc: "both local and remote",
-			in:   api.Response{TempPath: "/foobar", RemoteObject: api.RemoteObject{ID: "id"}},
+			in:   &api.Response{TempPath: "/foobar", RemoteObject: api.RemoteObject{ID: "id"}},
 		},
 	}
 
 	for _, tc := range testCases {
 		t.Run(tc.desc, func(t *testing.T) {
-			_, err := filestore.GetOpts(&tc.in)
+			_, err := filestore.GetOpts(tc.in)
 			require.Error(t, err, "expect input to be rejected")
 		})
 	}

workhorse/internal/git/archive.go

@@ -102,7 +102,7 @@ func (a *archive) Inject(w http.ResponseWriter, r *http.Request, sendData string
 
 	var archiveReader io.Reader
 
-	archiveReader, err = handleArchiveWithGitaly(r, params, format)
+	archiveReader, err = handleArchiveWithGitaly(r, &params, format)
 	if err != nil {
 		helper.Fail500(w, r, fmt.Errorf("operations.GetArchive: %v", err))
 		return
@@ -130,7 +130,7 @@ func (a *archive) Inject(w http.ResponseWriter, r *http.Request, sendData string
 	}
 }
 
-func handleArchiveWithGitaly(r *http.Request, params archiveParams, format gitalypb.GetArchiveRequest_Format) (io.Reader, error) {
+func handleArchiveWithGitaly(r *http.Request, params *archiveParams, format gitalypb.GetArchiveRequest_Format) (io.Reader, error) {
 	var request *gitalypb.GetArchiveRequest
 	ctx, c, err := gitaly.NewRepositoryClient(r.Context(), params.GitalyServer)
 	if err != nil {

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"
 
@@ -26,12 +27,16 @@ type Server struct {
 	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}
+	// 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 {

workhorse/internal/gitaly/gitaly_test.go

@@ -4,14 +4,32 @@ import (
 	"context"
 	"testing"
 
+	"github.com/sirupsen/logrus"
 	"github.com/stretchr/testify/require"
 	"google.golang.org/grpc/metadata"
 )
 
 func TestNewSmartHTTPClient(t *testing.T) {
-	ctx, _, err := NewSmartHTTPClient(context.Background(), serverFixture())
+	ctx, client, err := NewSmartHTTPClient(context.Background(), serverFixture())
 	require.NoError(t, err)
 	testOutgoingMetadata(t, ctx)
+
+	require.False(t, client.useSidechannel)
+	require.Nil(t, client.sidechannelRegistry)
+}
+
+func TestNewSmartHTTPClientWithSidechannel(t *testing.T) {
+	InitializeSidechannelRegistry(logrus.StandardLogger())
+
+	fixture := serverFixture()
+	fixture.Sidechannel = true
+
+	ctx, client, err := NewSmartHTTPClient(context.Background(), fixture)
+	require.NoError(t, err)
+	testOutgoingMetadata(t, ctx)
+
+	require.True(t, client.useSidechannel)
+	require.NotNil(t, client.sidechannelRegistry)
 }
 
 func TestNewBlobClient(t *testing.T) {

workhorse/internal/gitaly/smarthttp.go

@@ -5,11 +5,14 @@ import (
 	"fmt"
 	"io"
 
+	gitalyclient "gitlab.com/gitlab-org/gitaly/v14/client"
 	"gitlab.com/gitlab-org/gitaly/v14/proto/go/gitalypb"
 	"gitlab.com/gitlab-org/gitaly/v14/streamio"
 )
 
 type SmartHTTPClient struct {
+	useSidechannel      bool
+	sidechannelRegistry *gitalyclient.SidechannelRegistry
 	gitalypb.SmartHTTPServiceClient
 }
 
@@ -93,6 +96,14 @@ func (client *SmartHTTPClient) ReceivePack(ctx context.Context, repo *gitalypb.R
 }
 
 func (client *SmartHTTPClient) UploadPack(ctx context.Context, repo *gitalypb.Repository, clientRequest io.Reader, clientResponse io.Writer, gitConfigOptions []string, gitProtocol string) error {
+	if client.useSidechannel {
+		return client.runUploadPackWithSidechannel(ctx, repo, clientRequest, clientResponse, gitConfigOptions, gitProtocol)
+	}
+
+	return client.runUploadPack(ctx, repo, clientRequest, clientResponse, gitConfigOptions, gitProtocol)
+}
+
+func (client *SmartHTTPClient) runUploadPack(ctx context.Context, repo *gitalypb.Repository, clientRequest io.Reader, clientResponse io.Writer, gitConfigOptions []string, gitProtocol string) error {
 	stream, err := client.PostUploadPack(ctx)
 	if err != nil {
 		return err
@@ -137,3 +148,38 @@ func (client *SmartHTTPClient) UploadPack(ctx context.Context, repo *gitalypb.Re
 
 	return nil
 }
+
+func (client *SmartHTTPClient) runUploadPackWithSidechannel(ctx context.Context, repo *gitalypb.Repository, clientRequest io.Reader, clientResponse io.Writer, gitConfigOptions []string, gitProtocol string) error {
+	ctx, waiter := client.sidechannelRegistry.Register(ctx, func(conn gitalyclient.SidechannelConn) error {
+		if _, err := io.Copy(conn, clientRequest); err != nil {
+			return err
+		}
+
+		if err := conn.CloseWrite(); err != nil {
+			return fmt.Errorf("fail to signal sidechannel half-close: %w", err)
+		}
+
+		if _, err := io.Copy(clientResponse, conn); err != nil {
+			return err
+		}
+
+		return nil
+	})
+	defer waiter.Close()
+
+	rpcRequest := &gitalypb.PostUploadPackWithSidechannelRequest{
+		Repository:       repo,
+		GitConfigOptions: gitConfigOptions,
+		GitProtocol:      gitProtocol,
+	}
+
+	if _, err := client.PostUploadPackWithSidechannel(ctx, rpcRequest); err != nil {
+		return err
+	}
+
+	if err := waiter.Close(); err != nil {
+		return fmt.Errorf("fail to close sidechannel connection: %w", err)
+	}
+
+	return nil
+}

workhorse/internal/gitaly/unmarshal_test.go

@@ -3,6 +3,7 @@ package gitaly
 import (
 	"testing"
 
+	"github.com/golang/protobuf/proto" //lint:ignore SA1019 https://gitlab.com/gitlab-org/gitlab/-/issues/324868
 	"github.com/stretchr/testify/require"
 	"gitlab.com/gitlab-org/gitaly/v14/proto/go/gitalypb"
 )
@@ -11,25 +12,25 @@ func TestUnmarshalJSON(t *testing.T) {
 	testCases := []struct {
 		desc string
 		in   string
-		out  gitalypb.Repository
+		out  *gitalypb.Repository
 	}{
 		{
 			desc: "basic example",
 			in:   `{"relative_path":"foo/bar.git"}`,
-			out:  gitalypb.Repository{RelativePath: "foo/bar.git"},
+			out:  &gitalypb.Repository{RelativePath: "foo/bar.git"},
 		},
 		{
 			desc: "unknown field",
 			in:   `{"relative_path":"foo/bar.git","unknown_field":12345}`,
-			out:  gitalypb.Repository{RelativePath: "foo/bar.git"},
+			out:  &gitalypb.Repository{RelativePath: "foo/bar.git"},
 		},
 	}
 
 	for _, tc := range testCases {
 		t.Run(tc.desc, func(t *testing.T) {
-			result := gitalypb.Repository{}
-			require.NoError(t, UnmarshalJSON(tc.in, &result))
-			require.Equal(t, tc.out, result)
+			result := &gitalypb.Repository{}
+			require.NoError(t, UnmarshalJSON(tc.in, result))
+			require.True(t, proto.Equal(tc.out, result))
 		})
 	}
 }

workhorse/internal/testhelper/gitaly.go

 package testhelper
 
 import (
+	"bytes"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -11,6 +12,7 @@ import (
 	"github.com/golang/protobuf/jsonpb" //lint:ignore SA1019 https://gitlab.com/gitlab-org/gitlab/-/issues/324868
 	"github.com/golang/protobuf/proto"  //lint:ignore SA1019 https://gitlab.com/gitlab-org/gitlab/-/issues/324868
 	"golang.org/x/net/context"
+	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/metadata"
 	"google.golang.org/grpc/status"
@@ -23,6 +25,7 @@ type GitalyTestServer struct {
 	finalMessageCode codes.Code
 	sync.WaitGroup
 	LastIncomingMetadata metadata.MD
+	gitalypb.UnimplementedSmartHTTPServiceServer
 	gitalypb.UnimplementedRepositoryServiceServer
 	gitalypb.UnimplementedBlobServiceServer
 	gitalypb.UnimplementedDiffServiceServer
@@ -191,13 +194,14 @@ func (s *GitalyTestServer) PostUploadPack(stream gitalypb.SmartHTTPService_PostU
 		return err
 	}
 
-	jsonString, err := marshalJSON(req)
-	if err != nil {
+	marshaler := &jsonpb.Marshaler{}
+	jsonBytes := &bytes.Buffer{}
+	if err := marshaler.Marshal(jsonBytes, req); err != nil {
 		return err
 	}
 
 	if err := stream.Send(&gitalypb.PostUploadPackResponse{
-		Data: []byte(strings.Join([]string{jsonString}, "\000") + "\000"),
+		Data: append(jsonBytes.Bytes(), 0),
 	}); err != nil {
 		return err
 	}
@@ -229,6 +233,43 @@ func (s *GitalyTestServer) PostUploadPack(stream gitalypb.SmartHTTPService_PostU
 	return s.finalError()
 }
 
+// PostUploadPackWithSidechannel should be a part of smarthttp server in real
+// server. In workhorse, setting up a real sidechannel server is troublesome.
+// Therefore, we bring up a sidechannel server with a mock server exported via
+// gitalyclient.TestSidechannelServer. This is the handler for that mock
+// server.
+func PostUploadPackWithSidechannel(srv interface{}, stream grpc.ServerStream, conn io.ReadWriteCloser) error {
+	if method, ok := grpc.Method(stream.Context()); !ok || method != "/gitaly.SmartHTTPService/PostUploadPackWithSidechannel" {
+		return fmt.Errorf("unexpected method: %s", method)
+	}
+
+	var req gitalypb.PostUploadPackWithSidechannelRequest
+	if err := stream.RecvMsg(&req); err != nil {
+		return err
+	}
+
+	if err := validateRepository(req.GetRepository()); err != nil {
+		return err
+	}
+
+	marshaler := &jsonpb.Marshaler{}
+	jsonBytes := &bytes.Buffer{}
+	if err := marshaler.Marshal(jsonBytes, &req); err != nil {
+		return err
+	}
+
+	// Bounce back all data back to the client, plus flushing bytes
+	if _, err := conn.Write(append(jsonBytes.Bytes(), 0)); err != nil {
+		return err
+	}
+
+	if _, err := io.Copy(conn, conn); err != nil {
+		return err
+	}
+
+	return stream.SendMsg(&gitalypb.PostUploadPackWithSidechannelResponse{})
+}
+
 func (s *GitalyTestServer) CommitIsAncestor(ctx context.Context, in *gitalypb.CommitIsAncestorRequest) (*gitalypb.CommitIsAncestorResponse, error) {
 	return nil, nil
 }

workhorse/internal/upload/uploads_test.go

@@ -271,19 +271,19 @@ func TestUploadProcessingFile(t *testing.T) {
 
 	tests := []struct {
 		name    string
-		preauth api.Response
+		preauth *api.Response
 	}{
 		{
 			name:    "FileStore Upload",
-			preauth: api.Response{TempPath: tempPath},
+			preauth: &api.Response{TempPath: tempPath},
 		},
 		{
 			name:    "ObjectStore Upload",
-			preauth: api.Response{RemoteObject: api.RemoteObject{StoreURL: storeUrl}},
+			preauth: &api.Response{RemoteObject: api.RemoteObject{StoreURL: storeUrl}},
 		},
 		{
 			name: "ObjectStore and FileStore Upload",
-			preauth: api.Response{
+			preauth: &api.Response{
 				TempPath:     tempPath,
 				RemoteObject: api.RemoteObject{StoreURL: storeUrl},
 			},

workhorse/main.go

@@ -18,6 +18,7 @@ import (
 	"gitlab.com/gitlab-org/labkit/tracing"
 
 	"gitlab.com/gitlab-org/gitlab/workhorse/internal/config"
+	"gitlab.com/gitlab-org/gitlab/workhorse/internal/gitaly"
 	"gitlab.com/gitlab-org/gitlab/workhorse/internal/queueing"
 	"gitlab.com/gitlab-org/gitlab/workhorse/internal/redis"
 	"gitlab.com/gitlab-org/gitlab/workhorse/internal/secret"
@@ -233,6 +234,8 @@ func run(boot bootConfig, cfg config.Config) error {
 	}
 	defer accessCloser.Close()
 
+	gitaly.InitializeSidechannelRegistry(accessLogger)
+
 	up := wrapRaven(upstream.NewUpstream(cfg, accessLogger))
 
 	done := make(chan os.Signal, 1)

workhorse/main_test.go

@@ -814,6 +814,8 @@ func startWorkhorseServerWithConfig(cfg *config.Config) *httptest.Server {
 	testhelper.ConfigureSecret()
 	u := upstream.NewUpstream(*cfg, logrus.StandardLogger())
 
+	gitaly.InitializeSidechannelRegistry(logrus.StandardLogger())
+
 	return httptest.NewServer(u)
 }
 
@@ -834,6 +836,20 @@ func gitOkBody(t *testing.T) *api.Response {
 	}
 }
 
+func gitOkBodyWithSidechannel(t *testing.T) *api.Response {
+	return &api.Response{
+		GL_ID:       "user-123",
+		GL_USERNAME: "username",
+		Repository: gitalypb.Repository{
+			StorageName:  "default",
+			RelativePath: "foo/bar.git",
+		},
+		GitalyServer: gitaly.Server{
+			Sidechannel: true,
+		},
+	}
+}
+
 func httpGet(t *testing.T, url string, headers map[string]string) (*http.Response, string) {
 	req, err := http.NewRequest("GET", url, nil)
 	require.NoError(t, err)