Validate send quota again after acquiring writable channel (#1367)

* Validate send qouta again after acquring writable channel.

* Debug

* increase version only after settings have been updated

* clean-up

transport/http2_client.go

@@ -98,7 +98,8 @@ type http2Client struct {
 
 	initialWindowSize int32
 
-	bdpEst *bdpEstimator
+	bdpEst          *bdpEstimator
+	outQuotaVersion uint64
 
 	mu            sync.Mutex     // guard the following variables
 	state         transportState // the state of underlying connection
@@ -679,9 +680,13 @@ func (t *http2Client) GracefulClose() error {
 // if it improves the performance.
 func (t *http2Client) Write(s *Stream, data []byte, opts *Options) error {
 	r := bytes.NewBuffer(data)
+	var (
+		p   []byte
+		oqv uint64
+	)
 	for {
-		var p []byte
+		oqv = atomic.LoadUint64(&t.outQuotaVersion)
-		if r.Len() > 0 {
+		if r.Len() > 0 || p != nil {
 			size := http2MaxFrameLen
 			// Wait until the stream has some quota to send the data.
 			sq, err := wait(s.ctx, s.done, s.goAway, t.shutdownChan, s.sendQuotaPool.acquire())
@@ -699,7 +704,9 @@ func (t *http2Client) Write(s *Stream, data []byte, opts *Options) error {
 			if tq < size {
 				size = tq
 			}
-			p = r.Next(size)
+			if p == nil {
+				p = r.Next(size)
+			}
 			ps := len(p)
 			if ps < sq {
 				// Overbooked stream quota. Return it back.
@@ -744,6 +751,18 @@ func (t *http2Client) Write(s *Stream, data []byte, opts *Options) error {
 			return ContextErr(s.ctx.Err())
 		default:
 		}
+		if oqv != atomic.LoadUint64(&t.outQuotaVersion) {
+			// InitialWindowSize settings frame must have been received after we
+			// acquired send quota but before we got the writable channel.
+			// We must forsake this write.
+			t.sendQuotaPool.add(len(p))
+			s.sendQuotaPool.add(len(p))
+			if t.framer.adjustNumWriters(-1) == 0 {
+				t.controlBuf.put(&flushIO{})
+			}
+			t.writableChan <- 0
+			continue
+		}
 		if r.Len() == 0 && t.framer.adjustNumWriters(0) == 1 {
 			// Do a force flush iff this is last frame for the entire gRPC message
 			// and the caller is the only writer at this moment.
@@ -756,6 +775,7 @@ func (t *http2Client) Write(s *Stream, data []byte, opts *Options) error {
 			t.notifyError(err)
 			return connectionErrorf(true, err, "transport: %v", err)
 		}
+		p = nil
 		if t.framer.adjustNumWriters(-1) == 0 {
 			t.framer.flushWrite()
 		}
@@ -1216,6 +1236,7 @@ func (t *http2Client) applySettings(ss []http2.Setting) {
 			}
 			t.streamSendQuota = s.Val
 			t.mu.Unlock()
+			atomic.AddUint64(&t.outQuotaVersion, 1)
 		}
 	}
 }

transport/http2_server.go

@@ -99,7 +99,8 @@ type http2Server struct {
 
 	initialWindowSize int32
 
-	bdpEst *bdpEstimator
+	bdpEst          *bdpEstimator
+	outQuotaVersion uint64
 
 	mu            sync.Mutex // guard the following
 	state         transportState
@@ -828,10 +829,15 @@ func (t *http2Server) Write(s *Stream, data []byte, opts *Options) (err error) {
 		t.WriteHeader(s, nil)
 	}
 	r := bytes.NewBuffer(data)
+	var (
+		p   []byte
+		oqv uint64
+	)
 	for {
-		if r.Len() == 0 {
+		if r.Len() == 0 && p == nil {
 			return nil
 		}
+		oqv = atomic.LoadUint64(&t.outQuotaVersion)
 		size := http2MaxFrameLen
 		// Wait until the stream has some quota to send the data.
 		sq, err := wait(s.ctx, nil, nil, t.shutdownChan, s.sendQuotaPool.acquire())
@@ -849,7 +855,9 @@ func (t *http2Server) Write(s *Stream, data []byte, opts *Options) (err error) {
 		if tq < size {
 			size = tq
 		}
-		p := r.Next(size)
+		if p == nil {
+			p = r.Next(size)
+		}
 		ps := len(p)
 		if ps < sq {
 			// Overbooked stream quota. Return it back.
@@ -886,6 +894,18 @@ func (t *http2Server) Write(s *Stream, data []byte, opts *Options) (err error) {
 			return ContextErr(s.ctx.Err())
 		default:
 		}
+		if oqv != atomic.LoadUint64(&t.outQuotaVersion) {
+			// InitialWindowSize settings frame must have been received after we
+			// acquired send quota but before we got the writable channel.
+			// We must forsake this write.
+			t.sendQuotaPool.add(ps)
+			s.sendQuotaPool.add(ps)
+			if t.framer.adjustNumWriters(-1) == 0 {
+				t.controlBuf.put(&flushIO{})
+			}
+			t.writableChan <- 0
+			continue
+		}
 		var forceFlush bool
 		if r.Len() == 0 && t.framer.adjustNumWriters(0) == 1 && !opts.Last {
 			forceFlush = true
@@ -897,6 +917,7 @@ func (t *http2Server) Write(s *Stream, data []byte, opts *Options) (err error) {
 			t.Close()
 			return connectionErrorf(true, err, "transport: %v", err)
 		}
+		p = nil
 		if t.framer.adjustNumWriters(-1) == 0 {
 			t.framer.flushWrite()
 		}
@@ -914,6 +935,7 @@ func (t *http2Server) applySettings(ss []http2.Setting) {
 				stream.sendQuotaPool.add(int(s.Val) - int(t.streamSendQuota))
 			}
 			t.streamSendQuota = s.Val
+			atomic.AddUint64(&t.outQuotaVersion, 1)
 		}
 
 	}