limiter: move to internal/backend

internal/backend/limiter/limiter.go

@@ -0,0 +1,29 @@
+package limiter
+
+import (
+	"io"
+	"net/http"
+)
+
+// Limiter defines an interface that implementors can use to rate limit I/O
+// according to some policy defined and configured by the implementor.
+type Limiter interface {
+	// Upstream returns a rate limited reader that is intended to be used in
+	// uploads.
+	Upstream(r io.Reader) io.Reader
+
+	// UpstreamWriter returns a rate limited writer that is intended to be used
+	// in uploads.
+	UpstreamWriter(w io.Writer) io.Writer
+
+	// Downstream returns a rate limited reader that is intended to be used
+	// for downloads.
+	Downstream(r io.Reader) io.Reader
+
+	// Downstream returns a rate limited reader that is intended to be used
+	// for downloads.
+	DownstreamWriter(r io.Writer) io.Writer
+
+	// Transport returns an http.RoundTripper limited with the limiter.
+	Transport(http.RoundTripper) http.RoundTripper
+}

internal/backend/limiter/limiter_backend.go

@@ -0,0 +1,71 @@
+package limiter
+
+import (
+	"context"
+	"io"
+
+	"github.com/restic/restic/internal/restic"
+)
+
+// LimitBackend wraps a Backend and applies rate limiting to Load() and Save()
+// calls on the backend.
+func LimitBackend(be restic.Backend, l Limiter) restic.Backend {
+	return rateLimitedBackend{
+		Backend: be,
+		limiter: l,
+	}
+}
+
+type rateLimitedBackend struct {
+	restic.Backend
+	limiter Limiter
+}
+
+func (r rateLimitedBackend) Save(ctx context.Context, h restic.Handle, rd restic.RewindReader) error {
+	limited := limitedRewindReader{
+		RewindReader: rd,
+		limited:      r.limiter.Upstream(rd),
+	}
+
+	return r.Backend.Save(ctx, h, limited)
+}
+
+type limitedRewindReader struct {
+	restic.RewindReader
+
+	limited io.Reader
+}
+
+func (l limitedRewindReader) Read(b []byte) (int, error) {
+	return l.limited.Read(b)
+}
+
+func (r rateLimitedBackend) Load(ctx context.Context, h restic.Handle, length int, offset int64, consumer func(rd io.Reader) error) error {
+	return r.Backend.Load(ctx, h, length, offset, func(rd io.Reader) error {
+		return consumer(newDownstreamLimitedReader(rd, r.limiter))
+	})
+}
+
+type limitedReader struct {
+	io.Reader
+	writerTo io.WriterTo
+	limiter  Limiter
+}
+
+func newDownstreamLimitedReader(rd io.Reader, limiter Limiter) io.Reader {
+	lrd := limiter.Downstream(rd)
+	if wt, ok := rd.(io.WriterTo); ok {
+		lrd = &limitedReader{
+			Reader:   lrd,
+			writerTo: wt,
+			limiter:  limiter,
+		}
+	}
+	return lrd
+}
+
+func (l *limitedReader) WriteTo(w io.Writer) (int64, error) {
+	return l.writerTo.WriteTo(l.limiter.DownstreamWriter(w))
+}
+
+var _ restic.Backend = (*rateLimitedBackend)(nil)

internal/backend/limiter/limiter_backend_test.go

@@ -0,0 +1,109 @@
+package limiter
+
+import (
+	"bytes"
+	"context"
+	"crypto/rand"
+	"fmt"
+	"io"
+	"testing"
+
+	"github.com/restic/restic/internal/backend/mock"
+	"github.com/restic/restic/internal/restic"
+	rtest "github.com/restic/restic/internal/test"
+)
+
+func randomBytes(t *testing.T, size int) []byte {
+	data := make([]byte, size)
+	_, err := io.ReadFull(rand.Reader, data)
+	rtest.OK(t, err)
+	return data
+}
+
+func TestLimitBackendSave(t *testing.T) {
+	testHandle := restic.Handle{Type: restic.PackFile, Name: "test"}
+	data := randomBytes(t, 1234)
+
+	be := mock.NewBackend()
+	be.SaveFn = func(ctx context.Context, h restic.Handle, rd restic.RewindReader) error {
+		buf := new(bytes.Buffer)
+		_, err := io.Copy(buf, rd)
+		if err != nil {
+			return nil
+		}
+		if !bytes.Equal(data, buf.Bytes()) {
+			return fmt.Errorf("data mismatch")
+		}
+		return nil
+	}
+	limiter := NewStaticLimiter(Limits{42 * 1024, 42 * 1024})
+	limbe := LimitBackend(be, limiter)
+
+	rd := restic.NewByteReader(data, nil)
+	err := limbe.Save(context.TODO(), testHandle, rd)
+	rtest.OK(t, err)
+}
+
+type tracedReadWriteToCloser struct {
+	io.Reader
+	io.WriterTo
+	Traced bool
+}
+
+func newTracedReadWriteToCloser(rd *bytes.Reader) *tracedReadWriteToCloser {
+	return &tracedReadWriteToCloser{Reader: rd, WriterTo: rd}
+}
+
+func (r *tracedReadWriteToCloser) WriteTo(w io.Writer) (n int64, err error) {
+	r.Traced = true
+	return r.WriterTo.WriteTo(w)
+}
+
+func (r *tracedReadWriteToCloser) Close() error {
+	return nil
+}
+
+func TestLimitBackendLoad(t *testing.T) {
+	testHandle := restic.Handle{Type: restic.PackFile, Name: "test"}
+	data := randomBytes(t, 1234)
+
+	for _, test := range []struct {
+		innerWriteTo, outerWriteTo bool
+	}{{false, false}, {false, true}, {true, false}, {true, true}} {
+		be := mock.NewBackend()
+		src := newTracedReadWriteToCloser(bytes.NewReader(data))
+		be.OpenReaderFn = func(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
+			if length != 0 || offset != 0 {
+				return nil, fmt.Errorf("Not supported")
+			}
+			// test both code paths in WriteTo of limitedReadCloser
+			if test.innerWriteTo {
+				return src, nil
+			}
+			return newTracedReadCloser(src), nil
+		}
+		limiter := NewStaticLimiter(Limits{42 * 1024, 42 * 1024})
+		limbe := LimitBackend(be, limiter)
+
+		err := limbe.Load(context.TODO(), testHandle, 0, 0, func(rd io.Reader) error {
+			dataRead := new(bytes.Buffer)
+			// test both Read and WriteTo
+			if !test.outerWriteTo {
+				rd = newTracedReadCloser(rd)
+			}
+			_, err := io.Copy(dataRead, rd)
+			if err != nil {
+				return err
+			}
+			if !bytes.Equal(data, dataRead.Bytes()) {
+				return fmt.Errorf("read broken data")
+			}
+
+			return nil
+		})
+		rtest.OK(t, err)
+		rtest.Assert(t, src.Traced == (test.innerWriteTo && test.outerWriteTo),
+			"unexpected/missing writeTo call innerWriteTo %v outerWriteTo %v",
+			test.innerWriteTo, test.outerWriteTo)
+	}
+}

internal/backend/limiter/static_limiter.go

@@ -0,0 +1,114 @@
+package limiter
+
+import (
+	"io"
+	"net/http"
+
+	"github.com/juju/ratelimit"
+)
+
+type staticLimiter struct {
+	upstream   *ratelimit.Bucket
+	downstream *ratelimit.Bucket
+}
+
+// Limits represents static upload and download limits.
+// For both, zero means unlimited.
+type Limits struct {
+	UploadKb   int
+	DownloadKb int
+}
+
+// NewStaticLimiter constructs a Limiter with a fixed (static) upload and
+// download rate cap
+func NewStaticLimiter(l Limits) Limiter {
+	var (
+		upstreamBucket   *ratelimit.Bucket
+		downstreamBucket *ratelimit.Bucket
+	)
+
+	if l.UploadKb > 0 {
+		upstreamBucket = ratelimit.NewBucketWithRate(toByteRate(l.UploadKb), int64(toByteRate(l.UploadKb)))
+	}
+
+	if l.DownloadKb > 0 {
+		downstreamBucket = ratelimit.NewBucketWithRate(toByteRate(l.DownloadKb), int64(toByteRate(l.DownloadKb)))
+	}
+
+	return staticLimiter{
+		upstream:   upstreamBucket,
+		downstream: downstreamBucket,
+	}
+}
+
+func (l staticLimiter) Upstream(r io.Reader) io.Reader {
+	return l.limitReader(r, l.upstream)
+}
+
+func (l staticLimiter) UpstreamWriter(w io.Writer) io.Writer {
+	return l.limitWriter(w, l.upstream)
+}
+
+func (l staticLimiter) Downstream(r io.Reader) io.Reader {
+	return l.limitReader(r, l.downstream)
+}
+
+func (l staticLimiter) DownstreamWriter(w io.Writer) io.Writer {
+	return l.limitWriter(w, 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) {
+	type readCloser struct {
+		io.Reader
+		io.Closer
+	}
+
+	if req.Body != nil {
+		req.Body = &readCloser{
+			Reader: l.Upstream(req.Body),
+			Closer: req.Body,
+		}
+	}
+
+	res, err := rt.RoundTrip(req)
+
+	if res != nil && res.Body != nil {
+		res.Body = &readCloser{
+			Reader: l.Downstream(res.Body),
+			Closer: 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) limitReader(r io.Reader, b *ratelimit.Bucket) io.Reader {
+	if b == nil {
+		return r
+	}
+	return ratelimit.Reader(r, b)
+}
+
+func (l staticLimiter) limitWriter(w io.Writer, b *ratelimit.Bucket) io.Writer {
+	if b == nil {
+		return w
+	}
+	return ratelimit.Writer(w, b)
+}
+
+func toByteRate(val int) float64 {
+	return float64(val) * 1024.
+}

internal/backend/limiter/static_limiter_test.go

@@ -0,0 +1,105 @@
+package limiter
+
+import (
+	"bytes"
+	"crypto/rand"
+	"fmt"
+	"io"
+	"net/http"
+	"testing"
+
+	"github.com/restic/restic/internal/test"
+)
+
+func TestLimiterWrapping(t *testing.T) {
+	reader := bytes.NewReader([]byte{})
+	writer := new(bytes.Buffer)
+
+	for _, limits := range []Limits{
+		{0, 0},
+		{42, 0},
+		{0, 42},
+		{42, 42},
+	} {
+		limiter := NewStaticLimiter(limits)
+
+		mustWrapUpstream := limits.UploadKb > 0
+		test.Equals(t, limiter.Upstream(reader) != reader, mustWrapUpstream)
+		test.Equals(t, limiter.UpstreamWriter(writer) != writer, mustWrapUpstream)
+
+		mustWrapDownstream := limits.DownloadKb > 0
+		test.Equals(t, limiter.Downstream(reader) != reader, mustWrapDownstream)
+		test.Equals(t, limiter.DownstreamWriter(writer) != writer, mustWrapDownstream)
+	}
+}
+
+type tracedReadCloser struct {
+	io.Reader
+	Closed bool
+}
+
+func newTracedReadCloser(rd io.Reader) *tracedReadCloser {
+	return &tracedReadCloser{Reader: rd}
+}
+
+func (r *tracedReadCloser) Close() error {
+	r.Closed = true
+	return nil
+}
+
+func TestRoundTripperReader(t *testing.T) {
+	limiter := NewStaticLimiter(Limits{42 * 1024, 42 * 1024})
+	data := make([]byte, 1234)
+	_, err := io.ReadFull(rand.Reader, data)
+	test.OK(t, err)
+
+	send := newTracedReadCloser(bytes.NewReader(data))
+	var recv *tracedReadCloser
+
+	rt := limiter.Transport(roundTripper(func(req *http.Request) (*http.Response, error) {
+		buf := new(bytes.Buffer)
+		_, err := io.Copy(buf, req.Body)
+		if err != nil {
+			return nil, err
+		}
+		err = req.Body.Close()
+		if err != nil {
+			return nil, err
+		}
+
+		recv = newTracedReadCloser(bytes.NewReader(buf.Bytes()))
+		return &http.Response{Body: recv}, nil
+	}))
+
+	res, err := rt.RoundTrip(&http.Request{Body: send})
+	test.OK(t, err)
+
+	out := new(bytes.Buffer)
+	n, err := io.Copy(out, res.Body)
+	test.OK(t, err)
+	test.Equals(t, int64(len(data)), n)
+	test.OK(t, res.Body.Close())
+
+	test.Assert(t, send.Closed, "request body not closed")
+	test.Assert(t, recv.Closed, "result body not closed")
+	test.Assert(t, bytes.Equal(data, out.Bytes()), "data ping-pong failed")
+}
+
+func TestRoundTripperCornerCases(t *testing.T) {
+	limiter := NewStaticLimiter(Limits{42 * 1024, 42 * 1024})
+
+	rt := limiter.Transport(roundTripper(func(req *http.Request) (*http.Response, error) {
+		return &http.Response{}, nil
+	}))
+
+	res, err := rt.RoundTrip(&http.Request{})
+	test.OK(t, err)
+	test.Assert(t, res != nil, "round tripper returned no response")
+
+	rt = limiter.Transport(roundTripper(func(req *http.Request) (*http.Response, error) {
+		return nil, fmt.Errorf("error")
+	}))
+
+	_, err = rt.RoundTrip(&http.Request{})
+	test.Assert(t, err != nil, "round tripper lost an error")
+}