[ADDED] AllowCloseRetry option

In PR #360, we changed the default behavior of connection Close()
in that if the library failed to sent the close protocol or received
its response, the Close() could be retried. In order to do that,
the underlying NATS connection would not be closed.

This has side-effects in that the NATS connection would be left
opened or possibly reconnect when an user would have previously
called Close(), not check error, and expect NATS connection to
be closed.

The introduction of this option allow the default behavior to
remain the same, and users that do want to be able to call Close()
again on a failed call will need to set this option when creating
the connection.

Signed-off-by: Ivan Kozlovic <ivan@synadia.com>

stan.go

@@ -179,6 +179,21 @@ type Options struct {
 	// ConnectionLostCB specifies the handler to be invoked when the connection
 	// is permanently lost.
 	ConnectionLostCB ConnectionLostHandler
+
+	// AllowCloseRetry specifies that a failed connection Close() can be retried.
+	//
+	// By default, after the first call to Close(), the underlying NATS connection
+	// is closed (when owned by the library), regardless if the library gets a
+	// response from the server or not, and calling Close() again is a no-op.
+	// With AllowCloseRetry set to true, if the library fails to get a response
+	// from the close protocol, calling Close() again is possible and the library
+	// will try to resend the protocol. It means that the underlying NATS connection
+	// won't be closed until the library successfully gets a response from the server.
+	// This behavior can have side effects in that the underlying NATS connection
+	// may stay open (or reconnect) when otherwise it would have been closed after
+	// calling Close(). So AllowCloseRetry is disabled by default to maintain
+	// expected default behavior in regard with the underlying NATS connection state.
+	AllowCloseRetry bool
 }
 
 // GetDefaultOptions returns default configuration options for the client.
@@ -308,6 +323,15 @@ func SetConnectionLostHandler(handler ConnectionLostHandler) Option {
 	}
 }
 
+// AllowCloseRetry is an Option that allows a failed connection close to be retried.
+// See option AllowCloseRetry for more information.
+func AllowCloseRetry(allow bool) Option {
+	return func(o *Options) error {
+		o.AllowCloseRetry = allow
+		return nil
+	}
+}
+
 // A conn represents a bare connection to a stan cluster.
 type conn struct {
 	sync.RWMutex
@@ -682,6 +706,12 @@ func (sc *conn) Close() error {
 	if !sc.closed {
 		sc.closed = true
 		sc.cleanupOnClose(ErrConnectionClosed)
+		if !sc.opts.AllowCloseRetry {
+			sc.fullyClosed = true
+			if sc.ncOwned {
+				defer sc.nc.Close()
+			}
+		}
 	}
 
 	req := &pb.CloseRequest{ClientID: sc.clientID}
@@ -700,7 +730,7 @@ func (sc *conn) Close() error {
 	}
 	// As long as we got a valid response, we consider the connection fully closed.
 	sc.fullyClosed = true
-	if sc.ncOwned {
+	if sc.ncOwned && sc.opts.AllowCloseRetry {
 		sc.nc.Close()
 	}
 	if cr.Error != "" {

stan_test.go

@@ -1012,7 +1012,10 @@ func TestConnCloseError(t *testing.T) {
 	s := RunServer(clusterName)
 	defer s.Shutdown()
 
-	sc := NewDefaultConnection(t)
+	sc, err := Connect(clusterName, clientName, AllowCloseRetry(true))
+	if err != nil {
+		t.Fatalf("Error on connect: %v", err)
+	}
 	defer sc.Close()
 
 	nc, err := nats.Connect(nats.DefaultURL)