improve logging output

main.go

@@ -5,15 +5,11 @@ package main
 1. [x] serve HTTP /v1/instances/:app_id to retrieve ip:port pairs for given app
 2. [x] implement UDP proxy (one-way/two-way, fanout (& roundrobin))
 3. [x] implement upstream-conf.d file management
-4. [ ] implement TCP proxy (with pluggable impls: haproxy, lvs, ...)
-5. [ ] tcp-proxy: add `accept-proxy` support
-6. [ ] tcp-proxy: add `proxy-protocol` support
-7. [ ] logging: add readable up/down notices, such as:
-	- "APP_ID: Task $TASK_STATUS on host $HOSTNAME ($TASK_ID)."
-		with TASK_STATUS translating into readable ("killed", "finished", "running", ...)
-	- "APP_ID: Task on $HOSTNAME:$PORT is unhealthy ($TASK_ID)."
-	- "APP_ID: Task on $HOSTNAME:$PORT is healthy ($TASK_ID)."
-8. [ ] implement HTTP(S) gateway support
+4. [x] logging: add readable up/down notices, such as:
+5. [ ] implement TCP proxy (with pluggable impls: haproxy, lvs, ...)
+7. [ ] tcp-proxy: add `accept-proxy` support
+8. [ ] tcp-proxy: add `proxy-protocol` support
+9. [ ] implement HTTP(S) gateway support
 
 XXX Changes:
 
@@ -222,6 +218,7 @@ func (mmsd *mmsdService) setupEventBusListener() {
 
 		switch event.TaskStatus {
 		case marathon.TaskFinished, marathon.TaskFailed, marathon.TaskKilled, marathon.TaskLost:
+			log.Printf("App %v task %v on %v changed status. %v.\n", event.AppId, event.TaskId, event.Host, event.TaskStatus)
 			mmsd.Update(event.AppId, event.TaskId, false)
 		case marathon.TaskRunning:
 			// XXX we require our apps to always have health checks set,
@@ -235,15 +232,52 @@ func (mmsd *mmsdService) setupEventBusListener() {
 	sse.AddEventListener("health_status_changed_event", func(data string) {
 		var event marathon.HealthStatusChangedEvent
 		json.Unmarshal([]byte(data), &event)
+		app, err := mmsd.getMarathonApp(event.AppId)
+		if err != nil {
+			log.Printf("Failed to fetch Marathon app. %+v. %v\n", event, err)
+			return
+		}
+		if app == nil {
+			log.Printf("App %v not found anymore.\n", event.AppId)
+			return
+		}
+
+		task := app.GetTaskById(event.TaskId)
+		if task == nil {
+			log.Printf("App %v task %v not found anymore.\n", event.AppId, event.TaskId)
+			return
+		}
+
+		// app & task definitely do exist, so propagate health change event
+
+		if event.Alive {
+			log.Printf("App %v task %v on %v is healthy.\n", event.AppId, event.TaskId, task.Host)
+		} else {
+			log.Printf("App %v task %v on %v is unhealthy.\n", event.AppId, event.TaskId, task.Host)
+		}
+
 		mmsd.Update(event.AppId, event.TaskId, event.Alive)
 	})
 
 	go sse.RunForever()
 }
 
+func (mmsd *mmsdService) getMarathonApp(appID string) (*marathon.App, error) {
+	m, err := marathon.NewService(mmsd.MarathonIP, mmsd.MarathonPort)
+	if err != nil {
+		return nil, err
+	}
+
+	app, err := m.GetApp(appID)
+	if err != nil {
+		return nil, err
+	}
+
+	return app, nil
+}
+
 // enable/disable given app:task
 func (mmsd *mmsdService) Update(appID string, taskID string, alive bool) {
-	log.Printf("Update %v: %v (%v)\n", appID, taskID, alive)
 	m, err := marathon.NewService(mmsd.MarathonIP, mmsd.MarathonPort)
 	if err != nil {
 		log.Printf("Update: NewService(%q, %v) failed. %v\n", mmsd.MarathonIP, mmsd.MarathonPort, err)