transport: derive transport context from context.Background (#2930)

internal/transport/http2_server.go

@@ -65,8 +65,7 @@ var (
 // http2Server implements the ServerTransport interface with HTTP2.
 type http2Server struct {
 	ctx         context.Context
-	ctxDone     <-chan struct{} // Cache the context.Done() chan
-	cancel      context.CancelFunc
+	done        chan struct{}
 	conn        net.Conn
 	loopy       *loopyWriter
 	readerDone  chan struct{} // sync point to enable testing.
@@ -203,11 +202,10 @@ func newHTTP2Server(conn net.Conn, config *ServerConfig) (_ ServerTransport, err
 	if kep.MinTime == 0 {
 		kep.MinTime = defaultKeepalivePolicyMinTime
 	}
-	ctx, cancel := context.WithCancel(context.Background())
+	done := make(chan struct{})
 	t := &http2Server{
-		ctx:               ctx,
-		cancel:            cancel,
-		ctxDone:           ctx.Done(),
+		ctx:               context.Background(),
+		done:              done,
 		conn:              conn,
 		remoteAddr:        conn.RemoteAddr(),
 		localAddr:         conn.LocalAddr(),
@@ -228,7 +226,7 @@ func newHTTP2Server(conn net.Conn, config *ServerConfig) (_ ServerTransport, err
 		czData:            new(channelzData),
 		bufferPool:        newBufferPool(),
 	}
-	t.controlBuf = newControlBuffer(t.ctxDone)
+	t.controlBuf = newControlBuffer(t.done)
 	if dynamicWindow {
 		t.bdpEst = &bdpEstimator{
 			bdp:               initialWindowSize,
@@ -886,7 +884,7 @@ func (t *http2Server) Write(s *Stream, hdr []byte, data []byte, opts *Options) e
 			// TODO(mmukhi, dfawley): Should the server write also return io.EOF?
 			s.cancel()
 			select {
-			case <-t.ctx.Done():
+			case <-t.done:
 				return ErrConnClosing
 			default:
 			}
@@ -908,7 +906,7 @@ func (t *http2Server) Write(s *Stream, hdr []byte, data []byte, opts *Options) e
 	}
 	if err := s.wq.get(int32(len(hdr) + len(data))); err != nil {
 		select {
-		case <-t.ctx.Done():
+		case <-t.done:
 			return ErrConnClosing
 		default:
 		}
@@ -974,7 +972,7 @@ func (t *http2Server) keepalive() {
 				t.Close()
 				// Resetting the timer so that the clean-up doesn't deadlock.
 				maxAge.Reset(infinity)
-			case <-t.ctx.Done():
+			case <-t.done:
 			}
 			return
 		case <-keepalive.C:
@@ -996,7 +994,7 @@ func (t *http2Server) keepalive() {
 			}
 			t.controlBuf.put(p)
 			keepalive.Reset(t.kp.Timeout)
-		case <-t.ctx.Done():
+		case <-t.done:
 			return
 		}
 	}
@@ -1016,7 +1014,7 @@ func (t *http2Server) Close() error {
 	t.activeStreams = nil
 	t.mu.Unlock()
 	t.controlBuf.finish()
-	t.cancel()
+	close(t.done)
 	err := t.conn.Close()
 	if channelz.IsOn() {
 		channelz.RemoveEntry(t.channelzID)
@@ -1156,7 +1154,7 @@ func (t *http2Server) outgoingGoAwayHandler(g *goAway) (bool, error) {
 		select {
 		case <-t.drainChan:
 		case <-timer.C:
-		case <-t.ctx.Done():
+		case <-t.done:
 			return
 		}
 		t.controlBuf.put(&goAway{code: g.code, debugData: g.debugData})
@@ -1206,7 +1204,7 @@ func (t *http2Server) getOutFlowWindow() int64 {
 	select {
 	case sz := <-resp:
 		return int64(sz)
-	case <-t.ctxDone:
+	case <-t.done:
 		return -1
 	case <-timer.C:
 		return -2