dbus: use separate connection for signals

Author: bcwaldon

dbus/dbus.go

@@ -64,9 +64,14 @@ func PathBusEscape(path string) string {
 
 // Conn is a connection to systemd's dbus endpoint.
 type Conn struct {
+	// sysconn/sysobj are only used to call dbus methods
 	sysconn *dbus.Conn
 	sysobj  *dbus.Object
 
+	// sigconn/sigobj are only used to receive dbus signals
+	sigconn *dbus.Conn
+	sigobj  *dbus.Object
+
 	jobListener struct {
 		jobs map[dbus.ObjectPath]chan string
 		sync.Mutex
@@ -97,16 +102,23 @@ func newConnection(createBus func() (*dbus.Conn, error)) (*Conn, error) {
 		return nil, err
 	}
 
+	sigconn, err := dbusConnection(createBus)
+	if err != nil {
+		return nil, err
+	}
+
 	c := &Conn{
 		sysconn: sysconn,
 		sysobj:  systemdObject(sysconn),
+		sigconn: sigconn,
+		sigobj:  systemdObject(sigconn),
 	}
 
 	c.subscriber.ignore = make(map[dbus.ObjectPath]int64)
 	c.jobListener.jobs = make(map[dbus.ObjectPath]chan string)
 
 	// Setup the listeners on jobs so that we can get completions
-	c.sysconn.BusObject().Call("org.freedesktop.DBus.AddMatch", 0,
+	c.sigconn.BusObject().Call("org.freedesktop.DBus.AddMatch", 0,
 		"type='signal', interface='org.freedesktop.systemd1.Manager', member='JobRemoved'")
 
 	c.dispatch()

dbus/subscription.go

@@ -33,12 +33,12 @@ const (
 // systemd will automatically stop sending signals so there is no need to
 // explicitly call Unsubscribe().
 func (c *Conn) Subscribe() error {
-	c.sysconn.BusObject().Call("org.freedesktop.DBus.AddMatch", 0,
+	c.sigconn.BusObject().Call("org.freedesktop.DBus.AddMatch", 0,
 		"type='signal',interface='org.freedesktop.systemd1.Manager',member='UnitNew'")
-	c.sysconn.BusObject().Call("org.freedesktop.DBus.AddMatch", 0,
+	c.sigconn.BusObject().Call("org.freedesktop.DBus.AddMatch", 0,
 		"type='signal',interface='org.freedesktop.DBus.Properties',member='PropertiesChanged'")
 
-	err := c.sysobj.Call("org.freedesktop.systemd1.Manager.Subscribe", 0).Store()
+	err := c.sigobj.Call("org.freedesktop.systemd1.Manager.Subscribe", 0).Store()
 	if err != nil {
 		return err
 	}
@@ -48,7 +48,7 @@ func (c *Conn) Subscribe() error {
 
 // Unsubscribe this connection from systemd dbus events.
 func (c *Conn) Unsubscribe() error {
-	err := c.sysobj.Call("org.freedesktop.systemd1.Manager.Unsubscribe", 0).Store()
+	err := c.sigobj.Call("org.freedesktop.systemd1.Manager.Unsubscribe", 0).Store()
 	if err != nil {
 		return err
 	}
@@ -59,7 +59,7 @@ func (c *Conn) Unsubscribe() error {
 func (c *Conn) dispatch() {
 	ch := make(chan *dbus.Signal, signalBuffer)
 
-	c.sysconn.Signal(ch)
+	c.sigconn.Signal(ch)
 
 	go func() {
 		for {