Improve limiting HTTP based backends

cmd/restic/global.go

@@ -323,16 +323,11 @@ func OpenRepository(opts GlobalOptions) (*repository.Repository, error) {
 		return nil, errors.Fatal("Please specify repository location (-r)")
 	}
 
-	be, err := open(opts.Repo, opts.extended)
+	be, err := open(opts.Repo, opts, opts.extended)
 	if err != nil {
 		return nil, err
 	}
 
-	if opts.LimitUploadKb > 0 || opts.LimitDownloadKb > 0 {
-		debug.Log("rate limiting backend to %d KiB/s upload and %d KiB/s download", opts.LimitUploadKb, opts.LimitDownloadKb)
-		be = limiter.LimitBackend(be, limiter.NewStaticLimiter(opts.LimitUploadKb, opts.LimitDownloadKb))
-	}
-
 	be = backend.NewRetryBackend(be, 10, func(msg string, err error, d time.Duration) {
 		Warnf("%v returned error, retrying after %v: %v\n", msg, d, err)
 	})
@@ -532,7 +527,7 @@ func parseConfig(loc location.Location, opts options.Options) (interface{}, erro
 }
 
 // Open the backend specified by a location config.
-func open(s string, opts options.Options) (restic.Backend, error) {
+func open(s string, gopts GlobalOptions, opts options.Options) (restic.Backend, error) {
 	debug.Log("parsing location %v", s)
 	loc, err := location.Parse(s)
 	if err != nil {
@@ -551,11 +546,18 @@ func open(s string, opts options.Options) (restic.Backend, error) {
 		return nil, err
 	}
 
+	// wrap the transport so that the throughput via HTTP is limited
+	rt = limiter.NewStaticLimiter(gopts.LimitUploadKb, gopts.LimitDownloadKb).Transport(rt)
+
 	switch loc.Scheme {
 	case "local":
 		be, err = local.Open(cfg.(local.Config))
+		// wrap the backend in a LimitBackend so that the throughput is limited
+		be = limiter.LimitBackend(be, limiter.NewStaticLimiter(gopts.LimitUploadKb, gopts.LimitDownloadKb))
 	case "sftp":
 		be, err = sftp.Open(cfg.(sftp.Config), SuspendSignalHandler, InstallSignalHandler)
+		// wrap the backend in a LimitBackend so that the throughput is limited
+		be = limiter.LimitBackend(be, limiter.NewStaticLimiter(gopts.LimitUploadKb, gopts.LimitDownloadKb))
 	case "s3":
 		be, err = s3.Open(cfg.(s3.Config), rt)
 	case "gs":

internal/limiter/limiter.go

@@ -2,6 +2,7 @@ package limiter
 
 import (
 	"io"
+	"net/http"
 )
 
 // Limiter defines an interface that implementors can use to rate limit I/O
@@ -14,4 +15,7 @@ type Limiter interface {
 	// Downstream returns a rate limited reader that is intended to be used
 	// for downloads.
 	Downstream(r io.Reader) io.Reader
+
+	// Transport returns an http.RoundTripper limited with the limiter.
+	Transport(http.RoundTripper) http.RoundTripper
 }

internal/limiter/static_limiter.go

@@ -2,6 +2,7 @@ package limiter
 
 import (
 	"io"
+	"net/http"
 
 	"github.com/juju/ratelimit"
 )
@@ -41,6 +42,39 @@ func (l staticLimiter) Downstream(r io.Reader) io.Reader {
 	return l.limit(r, l.downstream)
 }
 
+type roundTripper func(*http.Request) (*http.Response, error)
+
+func (rt roundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	return rt(req)
+}
+
+func (l staticLimiter) roundTripper(rt http.RoundTripper, req *http.Request) (*http.Response, error) {
+	if req.Body != nil {
+		req.Body = limitedReadCloser{
+			limited:  l.Upstream(req.Body),
+			original: req.Body,
+		}
+	}
+
+	res, err := rt.RoundTrip(req)
+
+	if res != nil && res.Body != nil {
+		res.Body = limitedReadCloser{
+			limited:  l.Downstream(res.Body),
+			original: res.Body,
+		}
+	}
+
+	return res, err
+}
+
+// Transport returns an HTTP transport limited with the limiter l.
+func (l staticLimiter) Transport(rt http.RoundTripper) http.RoundTripper {
+	return roundTripper(func(req *http.Request) (*http.Response, error) {
+		return l.roundTripper(rt, req)
+	})
+}
+
 func (l staticLimiter) limit(r io.Reader, b *ratelimit.Bucket) io.Reader {
 	if b == nil {
 		return r