[FIXED] Subscribe timeout should send a close request

stan_test.go

@@ -1,4 +1,4 @@
-// Copyright 2016-2018 The NATS Authors
+// Copyright 2016-2021 The NATS Authors
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
@@ -2665,3 +2665,48 @@ func TestPublishAsyncTimeout(t *testing.T) {
 		t.Fatalf("Ack handler was invoked only %v out of %v", c, total)
 	}
 }
+
+func TestSubTimeout(t *testing.T) {
+	ns := natsd.RunDefaultServer()
+	defer ns.Shutdown()
+
+	opts := server.GetDefaultOptions()
+	opts.NATSServerURL = nats.DefaultURL
+	opts.ID = clusterName
+	s := runServerWithOpts(opts)
+	defer s.Shutdown()
+
+	sc, err := Connect(clusterName, clientName, ConnectWait(250*time.Millisecond))
+	if err != nil {
+		t.Fatalf("Error on connect: %v", err)
+	}
+	defer sc.Close()
+
+	// Setup a subscription on the close subscription subject so we can
+	// check that the library sends a close request on subscribe timeout.
+	nc := sc.NatsConn()
+	scc := sc.(*conn)
+	scc.Lock()
+	subj := scc.subCloseRequests
+	scc.Unlock()
+	sub, err := nc.SubscribeSync(subj)
+	if err != nil {
+		t.Fatalf("Error on unsubscribe: %v", err)
+	}
+
+	// Now shutdown STAN server just before trying to create a subscription.
+	s.Shutdown()
+	if _, err := sc.Subscribe("foo", func(_ *Msg) {}); err != ErrSubReqTimeout {
+		t.Fatalf("Expected %v, got %v", ErrSubReqTimeout, err)
+	}
+	// Now check that we got the subscription close request
+	msg, err := sub.NextMsg(250 * time.Millisecond)
+	if err != nil {
+		t.Fatalf("Error getting subscription close request: %v", err)
+	}
+	req := &pb.UnsubscribeRequest{}
+	req.Unmarshal(msg.Data)
+	if req.ClientID != clientName || req.Subject != "foo" || req.Inbox == "" {
+		t.Fatalf("Unexpected sub close request: %+v", req)
+	}
+}

sub.go

@@ -1,4 +1,4 @@
-// Copyright 2016-2018 The NATS Authors
+// Copyright 2016-2021 The NATS Authors
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
@@ -287,6 +287,22 @@ func (sc *conn) subscribe(subject, qgroup string, cb MsgHandler, options ...Subs
 	if err != nil {
 		sub.inboxSub.Unsubscribe()
 		if err == nats.ErrTimeout {
+			// On timeout, we don't know if the server got the request or
+			// not. So we will do best effort and send a "subscription close"
+			// request. However, since we don't have the AckInbox that is
+			// normally used to close a subscription, we will use the sub's
+			// inbox. Newer servers will fallback to lookup by inbox if they
+			// don't find the sub from the "AckInbox" lookup.
+			scr := &pb.UnsubscribeRequest{
+				ClientID: sc.clientID,
+				Subject:  subject,
+				Inbox:    sub.inbox,
+			}
+			b, _ := scr.Marshal()
+			// Send to the subscription close request, not the unsubscribe subject.
+			sc.nc.Publish(sc.subCloseRequests, b)
+
+			// Report this error to the user.
 			err = ErrSubReqTimeout
 		}
 		return nil, err