http2: connection pool periodically sends ping frame and closes the

connection if the ping is not responded on time.

DO NOT SUBMIT

Updates golang/go#31643

http2/client_conn_pool.go

@@ -7,9 +7,11 @@
 package http2
 
 import (
+	"context"
 	"crypto/tls"
 	"net/http"
 	"sync"
+	"time"
 )
 
 // ClientConnPool manages a pool of HTTP/2 client connections.
@@ -41,6 +43,16 @@ type clientConnPool struct {
 	dialing      map[string]*dialCall     // currently in-flight dials
 	keys         map[*ClientConn][]string
 	addConnCalls map[string]*addConnCall // in-flight addConnIfNeede calls
+
+	// TODO: figure out a way to allow user to configure pingPeriod and
+	// pingTimeout.
+	pingPeriod time.Duration // how often pings are sent on idle
+	// connections. The connection will be closed if response is not
+	// received within pingTimeout. 0 means no periodic pings.
+	pingTimeout time.Duration // connection will be force closed if a Ping
+	// response is not received within pingTimeout.
+	pingStops map[*ClientConn]chan struct{} // channels to stop the
+	// periodic Pings.
 }
 
 func (p *clientConnPool) GetClientConn(req *http.Request, addr string) (*ClientConn, error) {
@@ -219,13 +231,54 @@ func (p *clientConnPool) addConnLocked(key string, cc *ClientConn) {
 	if p.keys == nil {
 		p.keys = make(map[*ClientConn][]string)
 	}
+	if p.pingStops == nil {
+		p.pingStops = make(map[*ClientConn]chan struct{})
+	}
 	p.conns[key] = append(p.conns[key], cc)
 	p.keys[cc] = append(p.keys[cc], key)
+	if p.pingPeriod != 0 {
+		p.pingStops[cc] = p.pingConnection(key, cc)
+	}
+}
+
+// TODO: ping all connections at the same tick to save tickers?
+func (p *clientConnPool) pingConnection(key string, cc *ClientConn) chan struct{} {
+	done := make(chan struct{})
+	go func() {
+		ticker := time.NewTicker(p.pingPeriod)
+		defer ticker.Stop()
+		for {
+			select {
+			case <-done:
+				return
+			default:
+			}
+
+			select {
+			case <-done:
+				return
+			case <-ticker.C:
+				ctx, _ := context.WithTimeout(context.Background(), p.pingTimeout)
+				err := cc.Ping(ctx)
+				if err != nil {
+					cc.closeForLostPing()
+					p.MarkDead(cc)
+				}
+			}
+		}
+	}()
+	return done
 }
 
 func (p *clientConnPool) MarkDead(cc *ClientConn) {
 	p.mu.Lock()
 	defer p.mu.Unlock()
+
+	if done, ok := p.pingStops[cc]; ok {
+		close(done)
+		delete(p.pingStops, cc)
+	}
+
 	for _, key := range p.keys[cc] {
 		vv, ok := p.conns[key]
 		if !ok {

http2/transport.go

@@ -140,6 +140,10 @@ func ConfigureTransport(t1 *http.Transport) error {
 
 func configureTransport(t1 *http.Transport) (*Transport, error) {
 	connPool := new(clientConnPool)
+	// TODO: figure out a way to allow user to configure pingPeriod and
+	// pingTimeout.
+	connPool.pingPeriod = 5 * time.Second
+	connPool.pingTimeout = 1 * time.Second
 	t2 := &Transport{
 		ConnPool: noDialClientConnPool{connPool},
 		t1:       t1,
@@ -834,14 +838,12 @@ func (cc *ClientConn) sendGoAway() error {
 	return nil
 }
 
-// Close closes the client connection immediately.
-//
-// In-flight requests are interrupted. For a graceful shutdown, use Shutdown instead.
-func (cc *ClientConn) Close() error {
+// closes the client connection immediately. In-flight requests are interrupted.
+// err is sent to streams.
+func (cc *ClientConn) closeForError(err error) error {
 	cc.mu.Lock()
 	defer cc.cond.Broadcast()
 	defer cc.mu.Unlock()
-	err := errors.New("http2: client connection force closed via ClientConn.Close")
 	for id, cs := range cc.streams {
 		select {
 		case cs.resc <- resAndError{err: err}:
@@ -854,6 +856,20 @@ func (cc *ClientConn) Close() error {
 	return cc.tconn.Close()
 }
 
+// Close closes the client connection immediately.
+//
+// In-flight requests are interrupted. For a graceful shutdown, use Shutdown instead.
+func (cc *ClientConn) Close() error {
+	err := errors.New("http2: client connection force closed via ClientConn.Close")
+	return cc.closeForError(err)
+}
+
+// closes the client connection immediately. In-flight requests are interrupted.
+func (cc *ClientConn) closeForLostPing() error {
+	err := errors.New("http2: client connection force closed because ping frame is not responded")
+	return cc.closeForError(err)
+}
+
 const maxAllocFrameSize = 512 << 10
 
 // frameBuffer returns a scratch buffer suitable for writing DATA frames.

http2/transport_test.go

@@ -3244,6 +3244,32 @@ func TestTransportNoRaceOnRequestObjectAfterRequestComplete(t *testing.T) {
 	req.Header = http.Header{}
 }
 
+func TestTransportCloseAfterLostPing(t *testing.T) {
+	clientDone := make(chan struct{})
+	ct := newClientTester(t)
+	connPool := new(clientConnPool)
+	connPool.pingPeriod = 1 * time.Second
+	connPool.pingTimeout = 100 * time.Millisecond
+	connPool.t = ct.tr
+	ct.tr.ConnPool = connPool
+	ct.client = func() error {
+		defer ct.cc.(*net.TCPConn).CloseWrite()
+		defer close(clientDone)
+		req, _ := http.NewRequest("GET", "https://dummy.tld/", nil)
+		_, err := ct.tr.RoundTrip(req)
+		if err == nil || !strings.Contains(err.Error(), "ping frame is not responded") {
+			return fmt.Errorf("expected to get error about \"ping frame is not responded\", got %v", err)
+		}
+		return nil
+	}
+	ct.server = func() error {
+		ct.greet()
+		<-clientDone
+		return nil
+	}
+	ct.run()
+}
+
 func TestTransportRetryAfterGOAWAY(t *testing.T) {
 	var dialer struct {
 		sync.Mutex