trigger child reaper on start (#3487)

by seeding the incoming channel. This is required to collect the zombies created by switch-root.

lib/tether/tether.go

@@ -157,6 +157,9 @@ func (t *tether) setup() error {
 		log.Errorf("Unable to open PID file for %s : %s", os.Args[0], err)
 	}
 
+	// seed the incoming channel once to trigger child reaper. This is required to collect the zombies created by switch-root
+	t.triggerReaper()
+
 	return nil
 }
 

lib/tether/tether_darwin.go

@@ -41,6 +41,10 @@ func (t *tether) stopReaper() {
 	defer trace.End(trace.Begin("Shutting down child reaping"))
 }
 
+func (t *tether) triggerReaper() error {
+	return errors.New("Child reaping unimplemented on OSX")
+}
+
 // processEnvOS does OS specific checking and munging on the process environment prior to launch
 func (t *tether) processEnvOS(env []string) []string {
 	// TODO: figure out how we're going to specify user and pass all the settings along

lib/tether/tether_linux.go

@@ -151,6 +151,12 @@ func (t *tether) stopReaper() {
 	close(t.incoming)
 }
 
+func (t *tether) triggerReaper() {
+	defer trace.End(trace.Begin("Triggering child reaping"))
+
+	t.incoming <- syscall.SIGCHLD
+}
+
 func findExecutable(file string) error {
 	d, err := os.Stat(file)
 	if err != nil {

lib/tether/tether_windows.go

@@ -33,6 +33,10 @@ func (t *tether) stopReaper() {
 	defer trace.End(trace.Begin("Shutting down child reaping"))
 }
 
+func (t *tether) triggerReaper() error {
+	return errors.New("Child reaping unimplemented on windows")
+}
+
 func lookPath(file string, env []string, dir string) (string, error) {
 	return "", errors.New("unimplemented on windows")
 }