[ADDED] Force reconnect to the server

Signed-off-by: Piotr Piotrowski <piotr@synadia.com>

example_test.go

@@ -89,6 +89,19 @@ func ExampleConn_Subscribe() {
 	})
 }
 
+func ExampleConn_Reconnect() {
+	nc, _ := nats.Connect(nats.DefaultURL)
+	defer nc.Close()
+
+	nc.Subscribe("foo", func(m *nats.Msg) {
+		fmt.Printf("Received a message: %s\n", string(m.Data))
+	})
+
+	// Reconnect to the server.
+	// the subscription will be recreated after the reconnect.
+	nc.Reconnect()
+}
+
 // This Example shows a synchronous subscriber.
 func ExampleConn_SubscribeSync() {
 	nc, _ := nats.Connect(nats.DefaultURL)

nats.go

@@ -2161,6 +2161,47 @@ func (nc *Conn) waitForExits() {
 	nc.wg.Wait()
 }
 
+// Reconnect forces a reconnect attempt to the server.
+// This is a non-blocking call and will start the reconnect
+// process without waiting for it to complete.
+//
+// If the connection is already in the process of reconnecting,
+// this call will force an immediate reconnect attempt (bypassing
+// the current reconnect delay).
+func (nc *Conn) Reconnect() error {
+	nc.mu.Lock()
+	defer nc.mu.Unlock()
+
+	if nc.isClosed() {
+		return ErrConnectionClosed
+	}
+	if nc.isReconnecting() {
+		// if we're already reconnecting, force a reconnect attempt
+		// even if we're in the middle of a backoff
+		if nc.rqch != nil {
+			close(nc.rqch)
+		}
+		return nil
+	}
+
+	// Clear any queued pongs
+	nc.clearPendingFlushCalls()
+
+	// Clear any queued and blocking requests.
+	nc.clearPendingRequestCalls()
+
+	// Stop ping timer if set.
+	nc.stopPingTimer()
+
+	// Go ahead and make sure we have flushed the outbound
+	nc.bw.flush()
+	nc.conn.Close()
+
+	nc.changeConnStatus(RECONNECTING)
+	go nc.doReconnect(nil, true)
+	return nil
+}
+
 // ConnectedUrl reports the connected server's URL
 func (nc *Conn) ConnectedUrl() string {
 	if nc == nil {
@@ -2420,7 +2461,7 @@ func (nc *Conn) connect() (bool, error) {
 		nc.setup()
 		nc.changeConnStatus(RECONNECTING)
 		nc.bw.switchToPending()
-		go nc.doReconnect(ErrNoServers)
+		go nc.doReconnect(ErrNoServers, false)
 		err = nil
 	} else {
 		nc.current = nil
@@ -2720,7 +2761,7 @@ func (nc *Conn) stopPingTimer() {
 
 // Try to reconnect using the option parameters.
 // This function assumes we are allowed to reconnect.
-func (nc *Conn) doReconnect(err error) {
+func (nc *Conn) doReconnect(err error, forceReconnect bool) {
 	// We want to make sure we have the other watchers shutdown properly
 	// here before we proceed past this point.
 	nc.waitForExits()
@@ -2776,7 +2817,8 @@ func (nc *Conn) doReconnect(err error) {
 			break
 		}
 
-		doSleep := i+1 >= len(nc.srvPool)
+		doSleep := i+1 >= len(nc.srvPool) && !forceReconnect
+		forceReconnect = false
 		nc.mu.Unlock()
 
 		if !doSleep {
@@ -2803,6 +2845,12 @@ func (nc *Conn) doReconnect(err error) {
 			select {
 			case <-rqch:
 				rt.Stop()
+
+				// we need to reset the rqch channel to avoid
+				// closing a closed channel in the next iteration
+				nc.mu.Lock()
+				nc.rqch = make(chan struct{})
+				nc.mu.Unlock()
 			case <-rt.C:
 			}
 		}
@@ -2872,9 +2920,6 @@ func (nc *Conn) doReconnect(err error) {
 		// Done with the pending buffer
 		nc.bw.doneWithPending()
 
-		// This is where we are truly connected.
-		nc.status = CONNECTED
-
 		// Queue up the correct callback. If we are in initial connect state
 		// (using retry on failed connect), we will call the ConnectedCB,
 		// otherwise the ReconnectedCB.
@@ -2930,7 +2975,7 @@ func (nc *Conn) processOpErr(err error) {
 		// Clear any queued pongs, e.g. pending flush calls.
 		nc.clearPendingFlushCalls()
 
-		go nc.doReconnect(err)
+		go nc.doReconnect(err, false)
 		nc.mu.Unlock()
 		return
 	}

test/conn_test.go

@@ -2946,16 +2946,6 @@ func TestRetryOnFailedConnectWithTLSError(t *testing.T) {
 }
 
 func TestConnStatusChangedEvents(t *testing.T) {
-	waitForStatus := func(t *testing.T, ch chan nats.Status, expected nats.Status) {
-		select {
-		case s := <-ch:
-			if s != expected {
-				t.Fatalf("Expected status: %s; got: %s", expected, s)
-			}
-		case <-time.After(5 * time.Second):
-			t.Fatalf("Timeout waiting for status %q", expected)
-		}
-	}
 	t.Run("default events", func(t *testing.T) {
 		s := RunDefaultServer()
 		nc, err := nats.Connect(s.ClientURL())
@@ -2978,15 +2968,15 @@ func TestConnStatusChangedEvents(t *testing.T) {
 		time.Sleep(50 * time.Millisecond)
 
 		s.Shutdown()
-		waitForStatus(t, newStatus, nats.RECONNECTING)
+		WaitOnChannel(t, newStatus, nats.RECONNECTING)
 
 		s = RunDefaultServer()
 		defer s.Shutdown()
 
-		waitForStatus(t, newStatus, nats.CONNECTED)
+		WaitOnChannel(t, newStatus, nats.CONNECTED)
 
 		nc.Close()
-		waitForStatus(t, newStatus, nats.CLOSED)
+		WaitOnChannel(t, newStatus, nats.CLOSED)
 
 		select {
 		case s := <-newStatus:
@@ -3019,7 +3009,7 @@ func TestConnStatusChangedEvents(t *testing.T) {
 		s = RunDefaultServer()
 		defer s.Shutdown()
 		nc.Close()
-		waitForStatus(t, newStatus, nats.CLOSED)
+		WaitOnChannel(t, newStatus, nats.CLOSED)
 
 		select {
 		case s := <-newStatus:

test/helper_test.go

@@ -54,6 +54,18 @@ func WaitTime(ch chan bool, timeout time.Duration) error {
 	return errors.New("timeout")
 }
 
+func WaitOnChannel[T comparable](t *testing.T, ch <-chan T, expected T) {
+	t.Helper()
+	select {
+	case s := <-ch:
+		if s != expected {
+			t.Fatalf("Expected result: %v; got: %v", expected, s)
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatalf("Timeout waiting for result %v", expected)
+	}
+}
+
 func stackFatalf(t tLogger, f string, args ...any) {
 	lines := make([]string, 0, 32)
 	msg := fmt.Sprintf(f, args...)

test/reconnect_test.go

@@ -853,7 +853,7 @@ func TestAuthExpiredReconnect(t *testing.T) {
 
 	jwtCB := func() (string, error) {
 		claims := jwt.NewUserClaims("test")
-		claims.Expires = time.Now().Add(500 * time.Millisecond).Unix()
+		claims.Expires = time.Now().Add(time.Second).Unix()
 		claims.Subject = upub
 		jwt, err := claims.Encode(akp)
 		if err != nil {
@@ -884,21 +884,164 @@ func TestAuthExpiredReconnect(t *testing.T) {
 	case <-time.After(2 * time.Second):
 		t.Fatal("Did not get the auth expired error")
 	}
-	select {
-	case s := <-stasusCh:
-		if s != nats.RECONNECTING {
-			t.Fatalf("Expected to be in reconnecting state after jwt expires, got %v", s)
+	WaitOnChannel(t, stasusCh, nats.RECONNECTING)
+	WaitOnChannel(t, stasusCh, nats.CONNECTED)
+	nc.Close()
+}
+
+func TestForceReconnect(t *testing.T) {
+	s := RunDefaultServer()
+
+	nc, err := nats.Connect(s.ClientURL(), nats.ReconnectWait(10*time.Second))
+	if err != nil {
+		t.Fatalf("Unexpected error on connect: %v", err)
+	}
+	// defer nc.Close()
+
+	statusCh := nc.StatusChanged(nats.RECONNECTING, nats.CONNECTED)
+	defer close(statusCh)
+	newStatus := make(chan nats.Status, 10)
+	// non-blocking channel, so we need to be constantly listening
+	go func() {
+		for {
+			s, ok := <-statusCh
+			if !ok {
+				return
+			}
+			newStatus <- s
 		}
-	case <-time.After(2 * time.Second):
-		t.Fatal("Did not get the status change")
+	}()
+
+	sub, err := nc.SubscribeSync("foo")
+	if err != nil {
+		t.Fatalf("Error on subscribe: %v", err)
+	}
+	if err := nc.Publish("foo", []byte("msg")); err != nil {
+		t.Fatalf("Error on publish: %v", err)
+	}
+	_, err = sub.NextMsg(time.Second)
+	if err != nil {
+		t.Fatalf("Error getting message: %v", err)
+	}
+
+	// Force a reconnect
+	err = nc.Reconnect()
+	if err != nil {
+		t.Fatalf("Unexpected error on reconnect: %v", err)
+	}
+
+	WaitOnChannel(t, newStatus, nats.RECONNECTING)
+	WaitOnChannel(t, newStatus, nats.CONNECTED)
+
+	if err := nc.Publish("foo", []byte("msg")); err != nil {
+		t.Fatalf("Error on publish: %v", err)
 	}
+	_, err = sub.NextMsg(time.Second)
+	if err != nil {
+		t.Fatalf("Error getting message: %v", err)
+	}
+
+	// shutdown server and then force a reconnect
+	s.Shutdown()
+	WaitOnChannel(t, newStatus, nats.RECONNECTING)
+	_, err = sub.NextMsg(100 * time.Millisecond)
+	if err == nil {
+		t.Fatal("Expected error getting message")
+	}
+
+	// restart server
+	s = RunDefaultServer()
+	defer s.Shutdown()
+
+	if err := nc.Reconnect(); err != nil {
+		t.Fatalf("Unexpected error on reconnect: %v", err)
+	}
+	// wait for the reconnect
+	// because the connection has long ReconnectWait,
+	// if force reconnect does not work, the test will timeout
+	WaitOnChannel(t, newStatus, nats.CONNECTED)
+
+	if err := nc.Publish("foo", []byte("msg")); err != nil {
+		t.Fatalf("Error on publish: %v", err)
+	}
+	_, err = sub.NextMsg(time.Second)
+	if err != nil {
+		t.Fatalf("Error getting message: %v", err)
+	}
+	nc.Close()
+}
+
+func TestAuthExpiredForceReconnect(t *testing.T) {
+	ts := runTrustServer()
+	defer ts.Shutdown()
+
+	_, err := nats.Connect(ts.ClientURL())
+	if err == nil {
+		t.Fatalf("Expecting an error on connect")
+	}
+	ukp, err := nkeys.FromSeed(uSeed)
+	if err != nil {
+		t.Fatalf("Error creating user key pair: %v", err)
+	}
+	upub, err := ukp.PublicKey()
+	if err != nil {
+		t.Fatalf("Error getting user public key: %v", err)
+	}
+	akp, err := nkeys.FromSeed(aSeed)
+	if err != nil {
+		t.Fatalf("Error creating account key pair: %v", err)
+	}
+
+	jwtCB := func() (string, error) {
+		claims := jwt.NewUserClaims("test")
+		claims.Expires = time.Now().Add(time.Second).Unix()
+		claims.Subject = upub
+		jwt, err := claims.Encode(akp)
+		if err != nil {
+			return "", err
+		}
+		return jwt, nil
+	}
+	sigCB := func(nonce []byte) ([]byte, error) {
+		kp, _ := nkeys.FromSeed(uSeed)
+		sig, _ := kp.Sign(nonce)
+		return sig, nil
+	}
+
+	errCh := make(chan error, 1)
+	nc, err := nats.Connect(ts.ClientURL(), nats.UserJWT(jwtCB, sigCB), nats.ReconnectWait(10*time.Second),
+		nats.ErrorHandler(func(_ *nats.Conn, _ *nats.Subscription, err error) {
+			errCh <- err
+		}))
+	if err != nil {
+		t.Fatalf("Expected to connect, got %v", err)
+	}
+	defer nc.Close()
+	statusCh := nc.StatusChanged(nats.RECONNECTING, nats.CONNECTED)
+	defer close(statusCh)
+	newStatus := make(chan nats.Status, 10)
+	// non-blocking channel, so we need to be constantly listening
+	go func() {
+		for {
+			s, ok := <-statusCh
+			if !ok {
+				return
+			}
+			newStatus <- s
+		}
+	}()
+	time.Sleep(100 * time.Millisecond)
 	select {
-	case s := <-stasusCh:
-		if s != nats.CONNECTED {
-			t.Fatalf("Expected to reconnect, got %v", s)
+	case err := <-errCh:
+		if !errors.Is(err, nats.ErrAuthExpired) {
+			t.Fatalf("Expected auth expired error, got %v", err)
 		}
 	case <-time.After(2 * time.Second):
-		t.Fatal("Did not get the status change")
+		t.Fatal("Did not get the auth expired error")
 	}
-	nc.Close()
+	if err := nc.Reconnect(); err != nil {
+		t.Fatalf("Unexpected error on reconnect: %v", err)
+	}
+	WaitOnChannel(t, newStatus, nats.RECONNECTING)
+	WaitOnChannel(t, newStatus, nats.CONNECTED)
 }