GS: Use generic http transport

During the development of #1524 I discovered that the Google Cloud
Storage backend did not yet use the HTTP transport, so things such as
bandwidth limiting did not work. This commit does the necessary magic to
make the GS library use our HTTP transport.

cmd/restic/global.go

@@ -567,7 +567,7 @@ func open(s string, gopts GlobalOptions, opts options.Options) (restic.Backend,
 	case "s3":
 		be, err = s3.Open(cfg.(s3.Config), rt)
 	case "gs":
-		be, err = gs.Open(cfg.(gs.Config))
+		be, err = gs.Open(cfg.(gs.Config), rt)
 	case "azure":
 		be, err = azure.Open(cfg.(azure.Config), rt)
 	case "swift":
@@ -628,7 +628,7 @@ func create(s string, opts options.Options) (restic.Backend, error) {
 	case "s3":
 		return s3.Create(cfg.(s3.Config), rt)
 	case "gs":
-		return gs.Create(cfg.(gs.Config))
+		return gs.Create(cfg.(gs.Config), rt)
 	case "azure":
 		return azure.Create(cfg.(azure.Config), rt)
 	case "swift":

internal/backend/gs/gs.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"net/http"
 	"os"
 	"path"
 	"strings"
@@ -16,6 +17,7 @@ import (
 
 	"io/ioutil"
 
+	"golang.org/x/oauth2"
 	"golang.org/x/oauth2/google"
 	"google.golang.org/api/googleapi"
 	storage "google.golang.org/api/storage/v1"
@@ -41,7 +43,7 @@ type Backend struct {
 // Ensure that *Backend implements restic.Backend.
 var _ restic.Backend = &Backend{}
 
-func getStorageService(jsonKeyPath string) (*storage.Service, error) {
+func getStorageService(jsonKeyPath string, rt http.RoundTripper) (*storage.Service, error) {
 
 	raw, err := ioutil.ReadFile(jsonKeyPath)
 	if err != nil {
@@ -53,8 +55,18 @@ func getStorageService(jsonKeyPath string) (*storage.Service, error) {
 		return nil, err
 	}
 
-	client := conf.Client(context.TODO())
+	// create a new HTTP client
+	httpClient := &http.Client{
+		Transport: rt,
+	}
 
+	// create a now context with the HTTP client stored at the oauth2.HTTPClient key
+	ctx := context.WithValue(context.Background(), oauth2.HTTPClient, httpClient)
+
+	// then pass this context to Client(), which returns a new HTTP client
+	client := conf.Client(ctx)
+
+	// that we can then pass to New()
 	service, err := storage.New(client)
 	if err != nil {
 		return nil, err
@@ -65,10 +77,10 @@ func getStorageService(jsonKeyPath string) (*storage.Service, error) {
 
 const defaultListMaxItems = 1000
 
-func open(cfg Config) (*Backend, error) {
+func open(cfg Config, rt http.RoundTripper) (*Backend, error) {
 	debug.Log("open, config %#v", cfg)
 
-	service, err := getStorageService(cfg.JSONKeyPath)
+	service, err := getStorageService(cfg.JSONKeyPath, rt)
 	if err != nil {
 		return nil, errors.Wrap(err, "getStorageService")
 	}
@@ -95,8 +107,8 @@ func open(cfg Config) (*Backend, error) {
 }
 
 // Open opens the gs backend at the specified bucket.
-func Open(cfg Config) (restic.Backend, error) {
-	return open(cfg)
+func Open(cfg Config, rt http.RoundTripper) (restic.Backend, error) {
+	return open(cfg, rt)
 }
 
 // Create opens the gs backend at the specified bucket and attempts to creates
@@ -104,8 +116,8 @@ func Open(cfg Config) (restic.Backend, error) {
 //
 // The service account must have the "storage.buckets.create" permission to
 // create a bucket the does not yet exist.
-func Create(cfg Config) (restic.Backend, error) {
-	be, err := open(cfg)
+func Create(cfg Config, rt http.RoundTripper) (restic.Backend, error) {
+	be, err := open(cfg, rt)
 	if err != nil {
 		return nil, errors.Wrap(err, "open")
 	}

internal/backend/gs/gs_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/restic/restic/internal/backend"
 	"github.com/restic/restic/internal/backend/gs"
 	"github.com/restic/restic/internal/backend/test"
 	"github.com/restic/restic/internal/errors"
@@ -15,6 +16,11 @@ import (
 )
 
 func newGSTestSuite(t testing.TB) *test.Suite {
+	tr, err := backend.Transport(backend.TransportOptions{})
+	if err != nil {
+		t.Fatalf("cannot create transport for tests: %v", err)
+	}
+
 	return &test.Suite{
 		// do not use excessive data
 		MinimalData: true,
@@ -37,7 +43,7 @@ func newGSTestSuite(t testing.TB) *test.Suite {
 		Create: func(config interface{}) (restic.Backend, error) {
 			cfg := config.(gs.Config)
 
-			be, err := gs.Create(cfg)
+			be, err := gs.Create(cfg, tr)
 			if err != nil {
 				return nil, err
 			}
@@ -57,14 +63,14 @@ func newGSTestSuite(t testing.TB) *test.Suite {
 		// OpenFn is a function that opens a previously created temporary repository.
 		Open: func(config interface{}) (restic.Backend, error) {
 			cfg := config.(gs.Config)
-			return gs.Open(cfg)
+			return gs.Open(cfg, tr)
 		},
 
 		// CleanupFn removes data created during the tests.
 		Cleanup: func(config interface{}) error {
 			cfg := config.(gs.Config)
 
-			be, err := gs.Open(cfg)
+			be, err := gs.Open(cfg, tr)
 			if err != nil {
 				return err
 			}