Add config flag for deregistration behavior

Keep the default to deregister "always" on exit.
Can be set to "on-success" to only deregister when the process
exited cleanly, or was explicitly shutdown via "stop" or "kill".

bridge/bridge.go

@@ -57,7 +57,7 @@ func (b *Bridge) Remove(containerId string) {
 }
 
 func (b *Bridge) RemoveOnExit(containerId string) {
-	b.remove(containerId, b.didExitCleanly(containerId))
+	b.remove(containerId, b.config.DeregisterCheck == "always" || b.didExitCleanly(containerId))
 }
 
 func (b *Bridge) Refresh() {

bridge/types.go

@@ -24,6 +24,7 @@ type Config struct {
 	ForceTags       string
 	RefreshTtl      int
 	RefreshInterval int
+	DeregisterCheck string
 }
 
 type Service struct {

registrator.go

@@ -20,6 +20,7 @@ var refreshInterval = flag.Int("ttl-refresh", 0, "Frequency with which service T
 var refreshTtl = flag.Int("ttl", 0, "TTL for services (default is no expiry)")
 var forceTags = flag.String("tags", "", "Append tags for all registered services")
 var resyncInterval = flag.Int("resync", 0, "Frequency with which services are resynchronized")
+var deregister = flag.String("deregister", "always", "Deregister exited services \"always\" or \"on-success\"")
 
 func getopt(name, def string) string {
 	if env := os.Getenv(name); env != "" {
@@ -55,12 +56,17 @@ func main() {
 	docker, err := dockerapi.NewClient(getopt("DOCKER_HOST", "unix:///tmp/docker.sock"))
 	assert(err)
 
+	if *deregister != "always" && *deregister != "on-success" {
+		assert(errors.New("-deregister must be \"always\" or \"on-success\""))
+	}
+
 	b := bridge.New(docker, flag.Arg(0), bridge.Config{
 		HostIp:          *hostIp,
 		Internal:        *internal,
 		ForceTags:       *forceTags,
 		RefreshTtl:      *refreshTtl,
 		RefreshInterval: *refreshInterval,
+		DeregisterCheck: *deregister,
 	})
 
 	// Start event listener before listing containers to avoid missing anything