add an OpenStreamSync method to the streamsMap

streams_map.go

@@ -25,8 +25,10 @@ type streamsMap struct {
 	nextStream                protocol.StreamID // StreamID of the next Stream that will be returned by OpenStream()
 	highestStreamOpenedByPeer protocol.StreamID
 	nextStreamOrErrCond       sync.Cond
-	closeErr                  error
+	openStreamCond            sync.Cond
-	nextStreamToAccept        protocol.StreamID
+
+	closeErr           error
+	nextStreamToAccept protocol.StreamID
 
 	newStream newStreamLambda
 
@@ -52,6 +54,7 @@ func newStreamsMap(newStream newStreamLambda, pers protocol.Perspective, connect
 		connectionParameters: connectionParameters,
 	}
 	sm.nextStreamOrErrCond.L = &sm.mutex
+	sm.openStreamCond.L = &sm.mutex
 
 	if pers == protocol.PerspectiveClient {
 		sm.nextStream = 1
@@ -139,11 +142,7 @@ func (m *streamsMap) openRemoteStream(id protocol.StreamID) (*stream, error) {
 	return s, nil
 }
 
-// OpenStream opens the next available stream
+func (m *streamsMap) openStreamImpl() (*stream, error) {
-func (m *streamsMap) OpenStream() (*stream, error) {
-	m.mutex.Lock()
-	defer m.mutex.Unlock()
-
 	id := m.nextStream
 	if m.numOutgoingStreams >= m.connectionParameters.GetMaxOutgoingStreams() {
 		return nil, qerr.TooManyOpenStreams
@@ -165,6 +164,30 @@ func (m *streamsMap) OpenStream() (*stream, error) {
 	return s, nil
 }
 
+// OpenStream opens the next available stream
+func (m *streamsMap) OpenStream() (*stream, error) {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+
+	return m.openStreamImpl()
+}
+
+func (m *streamsMap) OpenStreamSync() (*stream, error) {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+
+	for {
+		str, err := m.openStreamImpl()
+		if err == nil {
+			return str, err
+		}
+		if err != nil && err != qerr.TooManyOpenStreams {
+			return nil, err
+		}
+		m.openStreamCond.Wait()
+	}
+}
+
 // AcceptStream returns the next stream opened by the peer
 // it blocks until a new stream is opened
 func (m *streamsMap) AcceptStream() (utils.Stream, error) {
@@ -290,6 +313,7 @@ func (m *streamsMap) RemoveStream(id protocol.StreamID) error {
 	}
 
 	delete(m.streams, id)
+	m.openStreamCond.Signal()
 	return nil
 }
 

streams_map_test.go

@@ -175,6 +175,13 @@ var _ = Describe("Streams Map", func() {
 					Expect(m.numOutgoingStreams).To(BeEquivalentTo(1))
 				})
 
+				It("errors if the stream can't be created", func() {
+					testErr := errors.New("test error")
+					m.newStream = func(protocol.StreamID) (*stream, error) { return nil, testErr }
+					_, err := m.OpenStream()
+					Expect(err).To(MatchError(testErr))
+				})
+
 				Context("counting streams", func() {
 					var maxNumStreams int
 
@@ -210,6 +217,49 @@ var _ = Describe("Streams Map", func() {
 						}
 					})
 				})
+
+				Context("opening streams synchronously", func() {
+					var maxNumStreams int
+
+					BeforeEach(func() {
+						maxNumStreams = int(cpm.GetMaxOutgoingStreams())
+					})
+
+					openMaxNumStreams := func() {
+						for i := 1; i <= maxNumStreams; i++ {
+							_, err := m.OpenStream()
+							Expect(err).NotTo(HaveOccurred())
+						}
+						_, err := m.OpenStream()
+						Expect(err).To(MatchError(qerr.TooManyOpenStreams))
+					}
+
+					It("waits until another stream is closed", func() {
+						openMaxNumStreams()
+						var returned bool
+						var str *stream
+						go func() {
+							defer GinkgoRecover()
+							var err error
+							str, err = m.OpenStreamSync()
+							Expect(err).ToNot(HaveOccurred())
+							returned = true
+						}()
+
+						Consistently(func() bool { return returned }).Should(BeFalse())
+						err := m.RemoveStream(6)
+						Expect(err).ToNot(HaveOccurred())
+						Eventually(func() bool { return returned }).Should(BeTrue())
+						Expect(str.StreamID()).To(Equal(protocol.StreamID(2*maxNumStreams + 2)))
+					})
+
+					It("errors if the stream can't be created", func() {
+						testErr := errors.New("test error")
+						m.newStream = func(protocol.StreamID) (*stream, error) { return nil, testErr }
+						_, err := m.OpenStreamSync()
+						Expect(err).To(MatchError(testErr))
+					})
+				})
 			})
 
 			Context("accepting streams", func() {