Handle canceling schedule and avoid recursive call

Using time.Ticker allow us to avoid recursive call that may end up in schedule running and possible deadlock if no routine is listening for cancel calls

switch to closing channel

management/server/scheduler.go

@@ -1,9 +1,10 @@
 package server
 
 import (
-	log "github.com/sirupsen/logrus"
 	"sync"
 	"time"
+
+	log "github.com/sirupsen/logrus"
 )
 
 // Scheduler is an interface which implementations can schedule and cancel jobs
@@ -55,14 +56,8 @@ func (wm *DefaultScheduler) cancel(ID string) bool {
 	cancel, ok := wm.jobs[ID]
 	if ok {
 		delete(wm.jobs, ID)
-		select {
-		case cancel <- struct{}{}:
-			log.Debugf("cancelled scheduled job %s", ID)
-		default:
-			log.Warnf("couldn't cancel job %s because there was no routine listening on the cancel event", ID)
-			return false
-		}
-
+		close(cancel)
+		log.Debugf("cancelled scheduled job %s", ID)
 	}
 	return ok
 }
@@ -90,25 +85,36 @@ func (wm *DefaultScheduler) Schedule(in time.Duration, ID string, job func() (ne
 		return
 	}
 
+	ticker := time.NewTicker(in)
+
 	wm.jobs[ID] = cancel
 	log.Debugf("scheduled a job %s to run in %s. There are %d total jobs scheduled.", ID, in.String(), len(wm.jobs))
 	go func() {
-		select {
-		case <-time.After(in):
-			log.Debugf("time to do a scheduled job %s", ID)
-			runIn, reschedule := job()
-			wm.mu.Lock()
-			defer wm.mu.Unlock()
-			delete(wm.jobs, ID)
-			if reschedule {
-				go wm.Schedule(runIn, ID, job)
+		for {
+			select {
+			case <-ticker.C:
+				log.Debugf("time to do a scheduled job %s", ID)
+				runIn, reschedule := job()
+				if !reschedule {
+					wm.mu.Lock()
+					defer wm.mu.Unlock()
+					delete(wm.jobs, ID)
+					log.Debugf("job %s is not scheduled to run again", ID)
+					ticker.Stop()
+					return
+				}
+				if runIn != in { // do we need to compare it with the original duration?
+					ticker.Reset(runIn)
+				}
+			case <-cancel:
+				ticker.Stop()
+				log.Debugf("stopped scheduled job %s ", ID)
+				wm.mu.Lock()
+				defer wm.mu.Unlock()
+				delete(wm.jobs, ID)
+				return
 			}
-		case <-cancel:
-			log.Debugf("stopped scheduled job %s ", ID)
-			wm.mu.Lock()
-			defer wm.mu.Unlock()
-			delete(wm.jobs, ID)
-			return
 		}
+
 	}()
 }