Minor refactor to campaign manager.

- Remove external invocation of worker goroutines into Run()
- Split Run() into smaller functions.

internal/manager/manager.go

@@ -181,14 +181,116 @@ func (m *Manager) HasMessenger(id string) bool {
 	return ok
 }
 
-// Run is a blocking function (and hence should be invoked as a goroutine)
+// Run is a blocking function (that should be invoked as a goroutine)
-// that scans the source db at regular intervals for pending campaigns,
+// that scans the data source at regular intervals for pending campaigns,
 // and queues them for processing. The process queue fetches batches of
 // subscribers and pushes messages to them for each queued campaign
 // until all subscribers are exhausted, at which point, a campaign is marked
 // as "finished".
 func (m *Manager) Run(tick time.Duration) {
-	go func() {
+	go m.scanCampaigns(tick)
+
+	// Spawn N message workers.
+	for i := 0; i < m.cfg.Concurrency; i++ {
+		go m.messageWorker()
+	}
+
+	// Fetch the next set of subscribers for a campaign and process them.
+	for c := range m.subFetchQueue {
+		has, err := m.nextSubscribers(c, m.cfg.BatchSize)
+		if err != nil {
+			m.logger.Printf("error processing campaign batch (%s): %v", c.Name, err)
+			continue
+		}
+
+		if has {
+			// There are more subscribers to fetch.
+			m.subFetchQueue <- c
+		} else if m.isCampaignProcessing(c.ID) {
+			// There are no more subscribers. Either the campaign status
+			// has changed or all subscribers have been processed.
+			newC, err := m.exhaustCampaign(c, "")
+			if err != nil {
+				m.logger.Printf("error exhausting campaign (%s): %v", c.Name, err)
+				continue
+			}
+			m.sendNotif(newC, newC.Status, "")
+		}
+	}
+}
+
+// messageWorker is a blocking function that listens to the message queue
+// and pushes out incoming messages on it to the messenger.
+func (m *Manager) messageWorker() {
+	// Counter to keep track of the message / sec rate limit.
+	numMsg := 0
+	for {
+		select {
+		// Campaign message.
+		case msg := <-m.campMsgQueue:
+			// Pause on hitting the message rate.
+			if numMsg >= m.cfg.MessageRate {
+				time.Sleep(time.Second)
+				numMsg = 0
+			}
+			numMsg++
+
+			err := m.messengers[msg.Campaign.MessengerID].Push(
+				msg.from, []string{msg.to}, msg.subject, msg.body, nil)
+			if err != nil {
+				m.logger.Printf("error sending message in campaign %s: %v", msg.Campaign.Name, err)
+
+				select {
+				case m.campMsgErrorQueue <- msgError{camp: msg.Campaign, err: err}:
+				default:
+				}
+			}
+
+		// Arbitrary message.
+		case msg := <-m.msgQueue:
+			err := m.messengers[msg.Messenger].Push(
+				msg.From, msg.To, msg.Subject, msg.Body, nil)
+			if err != nil {
+				m.logger.Printf("error sending message '%s': %v", msg.Subject, err)
+			}
+		}
+	}
+}
+
+// TemplateFuncs returns the template functions to be applied into
+// compiled campaign templates.
+func (m *Manager) TemplateFuncs(c *models.Campaign) template.FuncMap {
+	return template.FuncMap{
+		"TrackLink": func(url string, msg *CampaignMessage) string {
+			return m.trackLink(url, msg.Campaign.UUID, msg.Subscriber.UUID)
+		},
+		"TrackView": func(msg *CampaignMessage) template.HTML {
+			return template.HTML(fmt.Sprintf(`<img src="%s" alt="" />`,
+				fmt.Sprintf(m.cfg.ViewTrackURL, msg.Campaign.UUID, msg.Subscriber.UUID)))
+		},
+		"UnsubscribeURL": func(msg *CampaignMessage) string {
+			return msg.unsubURL
+		},
+		"OptinURL": func(msg *CampaignMessage) string {
+			// Add list IDs.
+			// TODO: Show private lists list on optin e-mail
+			return fmt.Sprintf(m.cfg.OptinURL, msg.Subscriber.UUID, "")
+		},
+		"MessageURL": func(msg *CampaignMessage) string {
+			return fmt.Sprintf(m.cfg.MessageURL, c.UUID, msg.Subscriber.UUID)
+		},
+		"Date": func(layout string) string {
+			if layout == "" {
+				layout = time.ANSIC
+			}
+			return time.Now().Format(layout)
+		},
+	}
+}
+
+// scanCampaigns is a blocking function that periodically scans the data source
+// for campaigns to process and dispatches them to the manager.
+func (m *Manager) scanCampaigns(tick time.Duration) {
 	t := time.NewTicker(tick)
 	for {
 		select {
@@ -239,103 +341,6 @@ func (m *Manager) Run(tick time.Duration) {
 			}
 		}
 	}
-	}()
-
-	// Fetch the next set of subscribers for a campaign and process them.
-	for c := range m.subFetchQueue {
-		has, err := m.nextSubscribers(c, m.cfg.BatchSize)
-		if err != nil {
-			m.logger.Printf("error processing campaign batch (%s): %v", c.Name, err)
-			continue
-		}
-
-		if has {
-			// There are more subscribers to fetch.
-			m.subFetchQueue <- c
-		} else if m.isCampaignProcessing(c.ID) {
-			// There are no more subscribers. Either the campaign status
-			// has changed or all subscribers have been processed.
-			newC, err := m.exhaustCampaign(c, "")
-			if err != nil {
-				m.logger.Printf("error exhausting campaign (%s): %v", c.Name, err)
-				continue
-			}
-			m.sendNotif(newC, newC.Status, "")
-		}
-	}
-}
-
-// SpawnWorkers spawns workers goroutines that push out messages.
-func (m *Manager) SpawnWorkers() {
-	for i := 0; i < m.cfg.Concurrency; i++ {
-		go func() {
-			// Counter to keep track of the message / sec rate limit.
-			numMsg := 0
-
-			for {
-				select {
-				// Campaign message.
-				case msg := <-m.campMsgQueue:
-					// Pause on hitting the message rate.
-					if numMsg >= m.cfg.MessageRate {
-						time.Sleep(time.Second)
-						numMsg = 0
-					}
-					numMsg++
-
-					err := m.messengers[msg.Campaign.MessengerID].Push(
-						msg.from, []string{msg.to}, msg.subject, msg.body, nil)
-					if err != nil {
-						m.logger.Printf("error sending message in campaign %s: %v", msg.Campaign.Name, err)
-
-						select {
-						case m.campMsgErrorQueue <- msgError{camp: msg.Campaign, err: err}:
-						default:
-						}
-					}
-
-				// Arbitrary message.
-				case msg := <-m.msgQueue:
-					err := m.messengers[msg.Messenger].Push(
-						msg.From, msg.To, msg.Subject, msg.Body, nil)
-					if err != nil {
-						m.logger.Printf("error sending message '%s': %v", msg.Subject, err)
-					}
-				}
-			}
-		}()
-	}
-}
-
-// TemplateFuncs returns the template functions to be applied into
-// compiled campaign templates.
-func (m *Manager) TemplateFuncs(c *models.Campaign) template.FuncMap {
-	return template.FuncMap{
-		"TrackLink": func(url string, msg *CampaignMessage) string {
-			return m.trackLink(url, msg.Campaign.UUID, msg.Subscriber.UUID)
-		},
-		"TrackView": func(msg *CampaignMessage) template.HTML {
-			return template.HTML(fmt.Sprintf(`<img src="%s" alt="" />`,
-				fmt.Sprintf(m.cfg.ViewTrackURL, msg.Campaign.UUID, msg.Subscriber.UUID)))
-		},
-		"UnsubscribeURL": func(msg *CampaignMessage) string {
-			return msg.unsubURL
-		},
-		"OptinURL": func(msg *CampaignMessage) string {
-			// Add list IDs.
-			// TODO: Show private lists list on optin e-mail
-			return fmt.Sprintf(m.cfg.OptinURL, msg.Subscriber.UUID, "")
-		},
-		"MessageURL": func(msg *CampaignMessage) string {
-			return fmt.Sprintf(m.cfg.MessageURL, c.UUID, msg.Subscriber.UUID)
-		},
-		"Date": func(layout string) string {
-			if layout == "" {
-				layout = time.ANSIC
-			}
-			return time.Now().Format(layout)
-		},
-	}
 }
 
 // addCampaign adds a campaign to the process queue.

main.go

@@ -142,7 +142,6 @@ func main() {
 	// Start the campaign workers. The campaign batches (fetch from DB, push out
 	// messages) get processed at the specified interval.
 	go app.manager.Run(time.Second * 5)
-	app.manager.SpawnWorkers()
 
 	// Start and run the app server.
 	initHTTPServer(app)