Merge pull request #1374 from restic/update-blazer

Update github.com/kurin/blazer

Gopkg.lock

@@ -88,8 +88,8 @@
 [[projects]]
   name = "github.com/kurin/blazer"
   packages = ["b2","base","internal/b2types","internal/blog"]
-  revision = "cad56a04490fe20c43548d70a5a9af2be53ff14e"
+  revision = "e269a1a17bb6aec278c06a57cb7e8f8d0d333e04"
-  version = "v0.2.0"
+  version = "v0.2.1"
 
 [[projects]]
   branch = "master"
@@ -214,6 +214,6 @@
 [solve-meta]
   analyzer-name = "dep"
   analyzer-version = 1
-  inputs-digest = "ea711bd1a9bfc8902b973a4de3a840f42536b9091fd8558980f44d6ca1622227"
+  inputs-digest = "abc33af201086afac21e33a2a7987a473daa6a229c3699ca13761f4d4fd7f52e"
   solver-name = "gps-cdcl"
   solver-version = 1

Gopkg.toml

@@ -72,3 +72,7 @@
 [[constraint]]
   branch = "master"
   name = "golang.org/x/sys"
+
+[[constraint]]
+  name = "github.com/kurin/blazer"
+  branch = "master"

vendor/github.com/kurin/blazer/.travis.yml

@@ -8,4 +8,6 @@ branches:
   - master
  
 before_script: go run internal/bin/cleanup/cleanup.go
-script: go test -v ./base ./b2 ./x/...
+script:
+ - go test -v ./base ./b2 ./x/...
+ - go vet -v ./base ./b2 ./x/...

vendor/github.com/kurin/blazer/b2/integration_test.go

@@ -27,6 +27,8 @@ import (
 	"sync/atomic"
 	"testing"
 	"time"
+
+	"github.com/kurin/blazer/x/transport"
 )
 
 const (
@@ -744,10 +746,10 @@ func (rt *rtCounter) RoundTrip(r *http.Request) (*http.Response, error) {
 }
 
 func TestAttrsNoRoundtrip(t *testing.T) {
-	rt := &rtCounter{rt: transport}
+	rt := &rtCounter{rt: defaultTransport}
-	transport = rt
+	defaultTransport = rt
 	defer func() {
-		transport = rt.rt
+		defaultTransport = rt.rt
 	}()
 
 	ctx := context.Background()
@@ -767,7 +769,7 @@ func TestAttrsNoRoundtrip(t *testing.T) {
 		t.Fatal(err)
 	}
 	if len(objs) != 1 {
-		t.Fatal("unexpected objects: got %d, want 1", len(objs))
+		t.Fatalf("unexpected objects: got %d, want 1", len(objs))
 	}
 
 	trips := rt.trips
@@ -842,7 +844,7 @@ func listObjects(ctx context.Context, f func(context.Context, int, *Cursor) ([]*
 	return ch
 }
 
-var transport = http.DefaultTransport
+var defaultTransport = http.DefaultTransport
 
 type eofTripper struct {
 	rt http.RoundTripper
@@ -919,9 +921,10 @@ func startLiveTest(ctx context.Context, t *testing.T) (*Bucket, func()) {
 		t.Skipf("B2_ACCOUNT_ID or B2_SECRET_KEY unset; skipping integration tests")
 		return nil, nil
 	}
-	ccport := &ccTripper{rt: transport, t: t}
+	ccport := &ccTripper{rt: defaultTransport, t: t}
 	tport := eofTripper{rt: ccport, t: t}
-	client, err := NewClient(ctx, id, key, FailSomeUploads(), ExpireSomeAuthTokens(), Transport(tport), UserAgent("b2-test"), UserAgent("integration-test"))
+	errport := transport.WithFailures(tport, transport.FailureRate(.25), transport.MatchPathSubstring("/b2_get_upload_url"), transport.Response(503))
+	client, err := NewClient(ctx, id, key, FailSomeUploads(), ExpireSomeAuthTokens(), Transport(errport), UserAgent("b2-test"), UserAgent("integration-test"))
 	if err != nil {
 		t.Fatal(err)
 		return nil, nil

vendor/github.com/kurin/blazer/base/base.go

@@ -43,7 +43,7 @@ import (
 
 const (
 	APIBase          = "https://api.backblazeb2.com"
-	DefaultUserAgent = "blazer/0.1.1"
+	DefaultUserAgent = "blazer/0.2.1"
 )
 
 type b2err struct {
@@ -131,25 +131,32 @@ const (
 
 func mkErr(resp *http.Response) error {
 	data, err := ioutil.ReadAll(resp.Body)
+	var msgBody string
 	if err != nil {
-		return err
+		msgBody = fmt.Sprintf("couldn't read message body: %v", err)
 	}
 	logResponse(resp, data)
 	msg := &b2types.ErrorMessage{}
 	if err := json.Unmarshal(data, msg); err != nil {
-		return err
+		if msgBody != "" {
+			msgBody = fmt.Sprintf("couldn't read message body: %v", err)
+		}
+	}
+	if msgBody == "" {
+		msgBody = msg.Msg
 	}
 	var retryAfter int
 	retry := resp.Header.Get("Retry-After")
 	if retry != "" {
 		r, err := strconv.ParseInt(retry, 10, 64)
 		if err != nil {
-			return err
+			r = 0
+			blog.V(1).Infof("couldn't parse retry-after header %q: %v", retry, err)
 		}
 		retryAfter = int(r)
 	}
 	return b2err{
-		msg:    msg.Msg,
+		msg:    msgBody,
 		retry:  retryAfter,
 		code:   resp.StatusCode,
 		method: resp.Request.Header.Get("X-Blazer-Method"),
@@ -222,6 +229,19 @@ type b2Options struct {
 	userAgent       string
 }
 
+func (o *b2Options) addHeaders(req *http.Request) {
+	if o.failSomeUploads {
+		req.Header.Add("X-Bz-Test-Mode", "fail_some_uploads")
+	}
+	if o.expireTokens {
+		req.Header.Add("X-Bz-Test-Mode", "expire_some_account_authorization_tokens")
+	}
+	if o.capExceeded {
+		req.Header.Add("X-Bz-Test-Mode", "force_cap_exceeded")
+	}
+	req.Header.Set("User-Agent", o.getUserAgent())
+}
+
 func (o *b2Options) getAPIBase() string {
 	if o.apiBase != "" {
 		return o.apiBase
@@ -268,14 +288,22 @@ type httpReply struct {
 	err  error
 }
 
-func makeNetRequest(req *http.Request, rt http.RoundTripper) <-chan httpReply {
+func makeNetRequest(ctx context.Context, req *http.Request, rt http.RoundTripper) (*http.Response, error) {
-	ch := make(chan httpReply)
+	req = req.WithContext(ctx)
-	go func() {
+	resp, err := rt.RoundTrip(req)
-		resp, err := rt.RoundTrip(req)
+	switch err {
-		ch <- httpReply{resp, err}
+	case nil:
-		close(ch)
+		return resp, nil
-	}()
+	case context.Canceled, context.DeadlineExceeded:
-	return ch
+		return nil, err
+	default:
+		method := req.Header.Get("X-Blazer-Method")
+		blog.V(2).Infof(">> %s uri: %v err: %v", method, req.URL, err)
+		return nil, b2err{
+			msg:   err.Error(),
+			retry: 1,
+		}
+	}
 }
 
 type requestBody struct {
@@ -351,38 +379,14 @@ func (o *b2Options) makeRequest(ctx context.Context, method, verb, uri string, b
 		}
 		req.Header.Set(k, v)
 	}
-	req.Header.Set("User-Agent", o.getUserAgent())
 	req.Header.Set("X-Blazer-Request-ID", fmt.Sprintf("%d", atomic.AddInt64(&reqID, 1)))
 	req.Header.Set("X-Blazer-Method", method)
-	if o.failSomeUploads {
+	o.addHeaders(req)
-		req.Header.Add("X-Bz-Test-Mode", "fail_some_uploads")
-	}
-	if o.expireTokens {
-		req.Header.Add("X-Bz-Test-Mode", "expire_some_account_authorization_tokens")
-	}
-	if o.capExceeded {
-		req.Header.Add("X-Bz-Test-Mode", "force_cap_exceeded")
-	}
-	cancel := make(chan struct{})
-	req.Cancel = cancel
 	logRequest(req, args)
-	ch := makeNetRequest(req, o.getTransport())
+	resp, err := makeNetRequest(ctx, req, o.getTransport())
-	var reply httpReply
+	if err != nil {
-	select {
+		return err
-	case reply = <-ch:
-	case <-ctx.Done():
-		close(cancel)
-		return ctx.Err()
 	}
-	if reply.err != nil {
-		// Connection errors are retryable.
-		blog.V(2).Infof(">> %s uri: %v err: %v", method, req.URL, reply.err)
-		return b2err{
-			msg:   reply.err.Error(),
-			retry: 1,
-		}
-	}
-	resp := reply.resp
 	defer resp.Body.Close()
 	if resp.StatusCode != 200 {
 		return mkErr(resp)
@@ -397,10 +401,11 @@ func (o *b2Options) makeRequest(ctx context.Context, method, verb, uri string, b
 		}
 		replyArgs = rbuf.Bytes()
 	} else {
-		replyArgs, err = ioutil.ReadAll(resp.Body)
+		ra, err := ioutil.ReadAll(resp.Body)
 		if err != nil {
-			return err
+			blog.V(1).Infof("%s: couldn't read response: %v", method, err)
 		}
+		replyArgs = ra
 	}
 	logResponse(resp, replyArgs)
 	return nil
@@ -1038,7 +1043,7 @@ func mkRange(offset, size int64) string {
 
 // DownloadFileByName wraps b2_download_file_by_name.
 func (b *Bucket) DownloadFileByName(ctx context.Context, name string, offset, size int64) (*FileReader, error) {
-	uri := fmt.Sprintf("%s/file/%s/%s", b.b2.downloadURI, b.Name, name)
+	uri := fmt.Sprintf("%s/file/%s/%s", b.b2.downloadURI, b.Name, escape(name))
 	req, err := http.NewRequest("GET", uri, nil)
 	if err != nil {
 		return nil, err
@@ -1046,25 +1051,16 @@ func (b *Bucket) DownloadFileByName(ctx context.Context, name string, offset, si
 	req.Header.Set("Authorization", b.b2.authToken)
 	req.Header.Set("X-Blazer-Request-ID", fmt.Sprintf("%d", atomic.AddInt64(&reqID, 1)))
 	req.Header.Set("X-Blazer-Method", "b2_download_file_by_name")
+	b.b2.opts.addHeaders(req)
 	rng := mkRange(offset, size)
 	if rng != "" {
 		req.Header.Set("Range", rng)
 	}
-	cancel := make(chan struct{})
-	req.Cancel = cancel
 	logRequest(req, nil)
-	ch := makeNetRequest(req, b.b2.opts.getTransport())
+	resp, err := makeNetRequest(ctx, req, b.b2.opts.getTransport())
-	var reply httpReply
+	if err != nil {
-	select {
+		return nil, err
-	case reply = <-ch:
-	case <-ctx.Done():
-		close(cancel)
-		return nil, ctx.Err()
 	}
-	if reply.err != nil {
-		return nil, reply.err
-	}
-	resp := reply.resp
 	logResponse(resp, nil)
 	if resp.StatusCode != 200 && resp.StatusCode != 206 {
 		defer resp.Body.Close()

vendor/github.com/kurin/blazer/base/integration_test.go

@@ -20,14 +20,14 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"net"
-	"net/http"
 	"os"
 	"reflect"
 	"strings"
 	"testing"
 	"time"
 
+	"github.com/kurin/blazer/x/transport"
+
 	"context"
 )
 
@@ -270,48 +270,7 @@ func TestStorage(t *testing.T) {
 	}
 }
 
-// This slow motion train wreck of a type exists to axe a net connection after
+func TestUploadAuthAfterConnectionHang(t *testing.T) {
-// N bytes have been written.  Because of the specific bug it's built to test,
-// it can't just *close* the connection, so it just sleeps forever.
-type wonkyNetConn struct {
-	net.Conn
-	ctx context.Context // implode once cancelled
-	die *bool           // only implode once
-	n   int             // bytes to allow before imploding, roughly
-	i   int             // bytes written
-}
-
-func (w *wonkyNetConn) Write(b []byte) (int, error) {
-	if w.i > w.n && w.ctx.Err() != nil && *w.die {
-		*w.die = false
-		select {}
-	}
-	n, err := w.Conn.Write(b)
-	w.i += n
-	return n, err
-}
-
-func newWonkyNetConn(ctx context.Context, die *bool, n int, netw, addr string) (net.Conn, error) {
-	conn, err := net.Dial(netw, addr)
-	if err != nil {
-		return nil, err
-	}
-	return &wonkyNetConn{
-		Conn: conn,
-		ctx:  ctx,
-		n:    n,
-		die:  die,
-	}, nil
-}
-
-func makeBadDialContext(ctx context.Context) func(context.Context, string, string) (net.Conn, error) {
-	die := true
-	return func(noCtx context.Context, network, addr string) (net.Conn, error) {
-		return newWonkyNetConn(ctx, &die, 10000, network, addr)
-	}
-}
-
-func TestBadUpload(t *testing.T) {
 	id := os.Getenv(apiID)
 	key := os.Getenv(apiKey)
 	if id == "" || key == "" {
@@ -319,19 +278,16 @@ func TestBadUpload(t *testing.T) {
 	}
 	ctx := context.Background()
 
-	octx, ocancel := context.WithCancel(ctx)
+	hung := make(chan struct{})
-	defer ocancel()
 
-	badTransport := &http.Transport{
+	// An http.RoundTripper that dies after sending ~10k bytes.
-		Proxy:                 http.ProxyFromEnvironment,
+	hang := func() {
-		DialContext:           makeBadDialContext(octx),
+		close(hung)
-		MaxIdleConns:          100,
+		select {}
-		IdleConnTimeout:       90 * time.Second,
-		TLSHandshakeTimeout:   10 * time.Second,
-		ExpectContinueTimeout: 1 * time.Second,
 	}
+	tport := transport.WithFailures(nil, transport.AfterNBytes(10000, hang))
 
-	b2, err := AuthorizeAccount(ctx, id, key, Transport(badTransport))
+	b2, err := AuthorizeAccount(ctx, id, key, Transport(tport))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -358,13 +314,13 @@ func TestBadUpload(t *testing.T) {
 		t.Error(err)
 	}
 	smallSHA1 := fmt.Sprintf("%x", hash.Sum(nil))
-	ocancel()
+
 	go func() {
 		ue.UploadFile(ctx, buf, buf.Len(), smallFileName, "application/octet-stream", smallSHA1, nil)
 		t.Fatal("this ought not to be reachable")
 	}()
 
-	time.Sleep(time.Second) // give this a chance to hang
+	<-hung
 
 	// Do the whole thing again with the same upload auth, before the remote end
 	// notices we're gone.
@@ -381,7 +337,97 @@ func TestBadUpload(t *testing.T) {
 		}
 	}
 	if Action(err) != AttemptNewUpload {
-		t.Error("Action(%v): got %v, want AttemptNewUpload", err, Action(err))
+		t.Errorf("Action(%v): got %v, want AttemptNewUpload", err, Action(err))
+	}
+}
+
+func TestCancelledContextCancelsHTTPRequest(t *testing.T) {
+	id := os.Getenv(apiID)
+	key := os.Getenv(apiKey)
+	if id == "" || key == "" {
+		t.Skipf("B2_ACCOUNT_ID or B2_SECRET_KEY unset; skipping integration tests")
+	}
+	ctx := context.Background()
+
+	tport := transport.WithFailures(nil, transport.MatchPathSubstring("b2_upload_file"), transport.FailureRate(1), transport.Stall(2*time.Second))
+
+	b2, err := AuthorizeAccount(ctx, id, key, Transport(tport))
+	if err != nil {
+		t.Fatal(err)
+	}
+	bname := id + "-" + bucketName
+	bucket, err := b2.CreateBucket(ctx, bname, "", nil, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		if err := bucket.DeleteBucket(ctx); err != nil {
+			t.Error(err)
+		}
+	}()
+	ue, err := bucket.GetUploadURL(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	smallFile := io.LimitReader(zReader{}, 1024*50) // 50k
+	hash := sha1.New()
+	buf := &bytes.Buffer{}
+	w := io.MultiWriter(hash, buf)
+	if _, err := io.Copy(w, smallFile); err != nil {
+		t.Error(err)
+	}
+	smallSHA1 := fmt.Sprintf("%x", hash.Sum(nil))
+	cctx, cancel := context.WithCancel(ctx)
+	go func() {
+		time.Sleep(1)
+		cancel()
+	}()
+	if _, err := ue.UploadFile(cctx, buf, buf.Len(), smallFileName, "application/octet-stream", smallSHA1, nil); err != context.Canceled {
+		t.Errorf("expected canceled context, but got %v", err)
+	}
+}
+
+func TestDeadlineExceededContextCancelsHTTPRequest(t *testing.T) {
+	id := os.Getenv(apiID)
+	key := os.Getenv(apiKey)
+	if id == "" || key == "" {
+		t.Skipf("B2_ACCOUNT_ID or B2_SECRET_KEY unset; skipping integration tests")
+	}
+	ctx := context.Background()
+
+	tport := transport.WithFailures(nil, transport.MatchPathSubstring("b2_upload_file"), transport.FailureRate(1), transport.Stall(2*time.Second))
+	b2, err := AuthorizeAccount(ctx, id, key, Transport(tport))
+	if err != nil {
+		t.Fatal(err)
+	}
+	bname := id + "-" + bucketName
+	bucket, err := b2.CreateBucket(ctx, bname, "", nil, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		if err := bucket.DeleteBucket(ctx); err != nil {
+			t.Error(err)
+		}
+	}()
+	ue, err := bucket.GetUploadURL(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	smallFile := io.LimitReader(zReader{}, 1024*50) // 50k
+	hash := sha1.New()
+	buf := &bytes.Buffer{}
+	w := io.MultiWriter(hash, buf)
+	if _, err := io.Copy(w, smallFile); err != nil {
+		t.Error(err)
+	}
+	smallSHA1 := fmt.Sprintf("%x", hash.Sum(nil))
+	cctx, cancel := context.WithTimeout(ctx, time.Second)
+	defer cancel()
+	if _, err := ue.UploadFile(cctx, buf, buf.Len(), smallFileName, "application/octet-stream", smallSHA1, nil); err != context.DeadlineExceeded {
+		t.Errorf("expected deadline exceeded error, but got %v", err)
 	}
 }
 
@@ -533,3 +579,72 @@ func TestEscapes(t *testing.T) {
 		}
 	}
 }
+
+func TestUploadDownloadFilenameEscaping(t *testing.T) {
+	filename := "file%foo.txt"
+
+	id := os.Getenv(apiID)
+	key := os.Getenv(apiKey)
+
+	if id == "" || key == "" {
+		t.Skipf("B2_ACCOUNT_ID or B2_SECRET_KEY unset; skipping integration tests")
+	}
+	ctx := context.Background()
+
+	// b2_authorize_account
+	b2, err := AuthorizeAccount(ctx, id, key, UserAgent("blazer-base-test"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// b2_create_bucket
+	bname := id + "-" + bucketName
+	bucket, err := b2.CreateBucket(ctx, bname, "", nil, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer func() {
+		// b2_delete_bucket
+		if err := bucket.DeleteBucket(ctx); err != nil {
+			t.Error(err)
+		}
+	}()
+
+	// b2_get_upload_url
+	ue, err := bucket.GetUploadURL(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// b2_upload_file
+	smallFile := io.LimitReader(zReader{}, 128)
+	hash := sha1.New()
+	buf := &bytes.Buffer{}
+	w := io.MultiWriter(hash, buf)
+	if _, err := io.Copy(w, smallFile); err != nil {
+		t.Error(err)
+	}
+	smallSHA1 := fmt.Sprintf("%x", hash.Sum(nil))
+	file, err := ue.UploadFile(ctx, buf, buf.Len(), filename, "application/octet-stream", smallSHA1, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer func() {
+		// b2_delete_file_version
+		if err := file.DeleteFileVersion(ctx); err != nil {
+			t.Error(err)
+		}
+	}()
+
+	// b2_download_file_by_name
+	fr, err := bucket.DownloadFileByName(ctx, filename, 0, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	lbuf := &bytes.Buffer{}
+	if _, err := io.Copy(lbuf, fr); err != nil {
+		t.Fatal(err)
+	}
+}

vendor/github.com/kurin/blazer/base/strings.go

@@ -15,67 +15,14 @@
 package base
 
 import (
-	"bytes"
+	"net/url"
-	"errors"
+	"strings"
-	"fmt"
 )
 
-func noEscape(c byte) bool {
-	switch c {
-	case '.', '_', '-', '/', '~', '!', '$', '\'', '(', ')', '*', ';', '=', ':', '@':
-		return true
-	}
-	return false
-}
-
 func escape(s string) string {
-	// cribbed from url.go, kinda
+	return strings.Replace(url.QueryEscape(s), "%2F", "/", -1)
-	b := &bytes.Buffer{}
-	for i := 0; i < len(s); i++ {
-		switch c := s[i]; {
-		case c == '/':
-			b.WriteByte(c)
-		case 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || '0' <= c && c <= '9':
-			b.WriteByte(c)
-		case noEscape(c):
-			b.WriteByte(c)
-		default:
-			fmt.Fprintf(b, "%%%X", c)
-		}
-	}
-	return b.String()
 }
 
 func unescape(s string) (string, error) {
-	b := &bytes.Buffer{}
+	return url.QueryUnescape(s)
-	for i := 0; i < len(s); i++ {
-		c := s[i]
-		switch c {
-		case '/':
-			b.WriteString("/")
-		case '+':
-			b.WriteString(" ")
-		case '%':
-			if len(s)-i < 3 {
-				return "", errors.New("unescape: bad encoding")
-			}
-			b.WriteByte(unhex(s[i+1])<<4 | unhex(s[i+2]))
-			i += 2
-		default:
-			b.WriteByte(c)
-		}
-	}
-	return b.String(), nil
-}
-
-func unhex(c byte) byte {
-	switch {
-	case '0' <= c && c <= '9':
-		return c - '0'
-	case 'a' <= c && c <= 'f':
-		return c - 'a' + 10
-	case 'A' <= c && c <= 'F':
-		return c - 'A' + 10
-	}
-	return 0
 }

vendor/github.com/kurin/blazer/base/strings_test.go

@@ -0,0 +1,52 @@
+package base
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestEncodeDecode(t *testing.T) {
+	// crashes identified by go-fuzz
+	origs := []string{
+		"&\x020000",
+		"&\x020000\x9c",
+		"&\x020\x9c0",
+		"&\x0230j",
+		"&\x02\x98000",
+		"&\x02\x983\xc8j00",
+		"00\x000",
+		"00\x0000",
+		"00\x0000000000000",
+		"\x11\x030",
+	}
+
+	for _, orig := range origs {
+		escaped := escape(orig)
+		unescaped, err := unescape(escaped)
+		if err != nil {
+			t.Errorf("%s: orig: %#v, escaped: %#v, unescaped: %#v\n", err.Error(), orig, escaped, unescaped)
+			continue
+		}
+
+		if unescaped != orig {
+			t.Errorf("expected: %#v, got: %#v", orig, unescaped)
+		}
+	}
+}
+
+// hook for go-fuzz: https://github.com/dvyukov/go-fuzz
+func Fuzz(data []byte) int {
+	orig := string(data)
+	escaped := escape(orig)
+
+	unescaped, err := unescape(escaped)
+	if err != nil {
+		return 0
+	}
+
+	if unescaped != orig {
+		panic(fmt.Sprintf("unescaped: \"%#v\", != orig: \"%#v\"", unescaped, orig))
+	}
+
+	return 1
+}

vendor/github.com/kurin/blazer/x/transport/transport.go

@@ -0,0 +1,207 @@
+// Copyright 2017, Google
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package transport provides http.RoundTrippers that may be useful to clients
+// of Blazer.
+package transport
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"math/rand"
+	"net/http"
+	"strings"
+	"sync/atomic"
+	"time"
+)
+
+// WithFailures returns an http.RoundTripper that wraps an existing
+// RoundTripper, causing failures according to the options given.  If rt is
+// nil, the http.DefaultTransport is wrapped.
+func WithFailures(rt http.RoundTripper, opts ...FailureOption) http.RoundTripper {
+	if rt == nil {
+		rt = http.DefaultTransport
+	}
+	o := &options{
+		rt: rt,
+	}
+	for _, opt := range opts {
+		opt(o)
+	}
+	return o
+}
+
+type options struct {
+	pathSubstrings []string
+	failureRate    float64
+	status         int
+	stall          time.Duration
+	rt             http.RoundTripper
+	msg            string
+	trg            *triggerReaderGroup
+}
+
+func (o *options) doRequest(req *http.Request) (*http.Response, error) {
+	if o.trg != nil && req.Body != nil {
+		req.Body = o.trg.new(req.Body)
+	}
+	resp, err := o.rt.RoundTrip(req)
+	if resp != nil && o.trg != nil {
+		resp.Body = o.trg.new(resp.Body)
+	}
+	return resp, err
+}
+
+func (o *options) RoundTrip(req *http.Request) (*http.Response, error) {
+	// TODO: fix triggering conditions
+	if rand.Float64() > o.failureRate {
+		return o.doRequest(req)
+	}
+
+	var match bool
+	if len(o.pathSubstrings) == 0 {
+		match = true
+	}
+	for _, ss := range o.pathSubstrings {
+		if strings.Contains(req.URL.Path, ss) {
+			match = true
+			break
+		}
+	}
+	if !match {
+		return o.doRequest(req)
+	}
+
+	if o.status > 0 {
+		resp := &http.Response{
+			Status:     fmt.Sprintf("%d %s", o.status, http.StatusText(o.status)),
+			StatusCode: o.status,
+			Body:       ioutil.NopCloser(strings.NewReader(o.msg)),
+			Request:    req,
+		}
+		return resp, nil
+	}
+
+	if o.stall > 0 {
+		ctx := req.Context()
+		select {
+		case <-time.After(o.stall):
+		case <-ctx.Done():
+		}
+	}
+	return o.doRequest(req)
+}
+
+// A FailureOption specifies the kind of failure that the RoundTripper should
+// display.
+type FailureOption func(*options)
+
+// MatchPathSubstring restricts the RoundTripper to URLs whose paths contain
+// the given string.  The default behavior is to match all paths.
+func MatchPathSubstring(s string) FailureOption {
+	return func(o *options) {
+		o.pathSubstrings = append(o.pathSubstrings, s)
+	}
+}
+
+// FailureRate causes the RoundTripper to fail a certain percentage of the
+// time.  rate should be a number between 0 and 1, where 0 will never fail and
+// 1 will always fail.  The default is never to fail.
+func FailureRate(rate float64) FailureOption {
+	return func(o *options) {
+		o.failureRate = rate
+	}
+}
+
+// Response simulates a given status code.  The returned http.Response will
+// have its Status, StatusCode, and Body (with any predefined message) set.
+func Response(status int) FailureOption {
+	return func(o *options) {
+		o.status = status
+	}
+}
+
+// Stall simulates a network connection failure by stalling for the given
+// duration.
+func Stall(dur time.Duration) FailureOption {
+	return func(o *options) {
+		o.stall = dur
+	}
+}
+
+// If a specific Response is requested, the body will have the given message
+// set.
+func Body(msg string) FailureOption {
+	return func(o *options) {
+		o.msg = msg
+	}
+}
+
+// Trigger will raise the RoundTripper's failure rate to 100% when the given
+// context is closed.
+func Trigger(ctx context.Context) FailureOption {
+	return func(o *options) {
+		go func() {
+			<-ctx.Done()
+			o.failureRate = 1
+		}()
+	}
+}
+
+// AfterNBytes will call effect once (roughly) n bytes have gone over the wire.
+// Both sent and received bytes are counted against the total.  Only bytes in
+// the body of an HTTP request are currently counted; this may change in the
+// future.  effect will only be called once, and it will block (allowing
+// callers to simulate connection hangs).
+func AfterNBytes(n int, effect func()) FailureOption {
+	return func(o *options) {
+		o.trg = &triggerReaderGroup{
+			bytes:   int64(n),
+			trigger: effect,
+		}
+	}
+}
+
+type triggerReaderGroup struct {
+	bytes     int64
+	trigger   func()
+	triggered int64
+}
+
+func (rg *triggerReaderGroup) new(rc io.ReadCloser) io.ReadCloser {
+	return &triggerReader{
+		ReadCloser: rc,
+		bytes:      &rg.bytes,
+		trigger:    rg.trigger,
+		triggered:  &rg.triggered,
+	}
+}
+
+type triggerReader struct {
+	io.ReadCloser
+	bytes     *int64
+	trigger   func()
+	triggered *int64
+}
+
+func (r *triggerReader) Read(p []byte) (int, error) {
+	n, err := r.ReadCloser.Read(p)
+	if atomic.AddInt64(r.bytes, -int64(n)) < 0 && atomic.CompareAndSwapInt64(r.triggered, 0, 1) {
+		// Can't use sync.Once because it blocks for *all* callers until Do returns.
+		r.trigger()
+	}
+	return n, err
+}