refactor(worker): use atomic state to simplify job control

worker/job.go

@@ -3,6 +3,7 @@ package worker
 import (
 	"errors"
 	"fmt"
+	"sync/atomic"
 
 	tunasync "github.com/tuna/tunasync/internal"
 )
@@ -26,22 +27,29 @@ type jobMessage struct {
 	schedule bool
 }
 
+const (
+	// empty state
+	stateNone uint32 = iota
+	// ready to run, able to schedule
+	stateReady
+	// paused by jobStop
+	statePaused
+	// disabled by jobDisable
+	stateDisabled
+)
+
 type mirrorJob struct {
-	provider   mirrorProvider
-	ctrlChan   chan ctrlAction
-	disabled   chan empty
-	started    bool
-	schedule   bool
-	isDisabled bool
+	provider mirrorProvider
+	ctrlChan chan ctrlAction
+	disabled chan empty
+	state    uint32
 }
 
 func newMirrorJob(provider mirrorProvider) *mirrorJob {
 	return &mirrorJob{
-		provider:   provider,
-		ctrlChan:   make(chan ctrlAction, 1),
-		started:    false,
-		schedule:   false,
-		isDisabled: false,
+		provider: provider,
+		ctrlChan: make(chan ctrlAction, 1),
+		state:    stateNone,
 	}
 }
 
@@ -49,6 +57,14 @@ func (m *mirrorJob) Name() string {
 	return m.provider.Name()
 }
 
+func (m *mirrorJob) State() uint32 {
+	return atomic.LoadUint32(&(m.state))
+}
+
+func (m *mirrorJob) SetState(state uint32) {
+	atomic.StoreUint32(&(m.state), state)
+}
+
 // runMirrorJob is the goroutine where syncing job runs in
 // arguments:
 //    provider: mirror provider object
@@ -61,8 +77,7 @@ func (m *mirrorJob) Run(managerChan chan<- jobMessage, semaphore chan empty) err
 	m.disabled = make(chan empty)
 	defer func() {
 		close(m.disabled)
-		m.schedule = false
-		m.isDisabled = true
+		m.SetState(stateDisabled)
 	}()
 
 	provider := m.provider
@@ -192,7 +207,7 @@ func (m *mirrorJob) Run(managerChan chan<- jobMessage, semaphore chan empty) err
 	}
 
 	for {
-		if m.started {
+		if m.State() == stateReady {
 			kill := make(chan empty)
 			jobDone := make(chan empty)
 			go runJob(kill, jobDone)
@@ -204,24 +219,21 @@ func (m *mirrorJob) Run(managerChan chan<- jobMessage, semaphore chan empty) err
 			case ctrl := <-m.ctrlChan:
 				switch ctrl {
 				case jobStop:
-					m.schedule = false
-					m.started = false
+					m.SetState(statePaused)
 					close(kill)
 					<-jobDone
 				case jobDisable:
-					m.schedule = false
-					m.isDisabled = true
-					m.started = false
+					m.SetState(stateDisabled)
 					close(kill)
 					<-jobDone
 					return nil
 				case jobRestart:
-					m.started = true
+					m.SetState(stateReady)
 					close(kill)
 					<-jobDone
 					continue
 				case jobStart:
-					m.started = true
+					m.SetState(stateReady)
 					goto _wait_for_job
 				default:
 					// TODO: implement this
@@ -234,21 +246,14 @@ func (m *mirrorJob) Run(managerChan chan<- jobMessage, semaphore chan empty) err
 		ctrl := <-m.ctrlChan
 		switch ctrl {
 		case jobStop:
-			m.schedule = false
-			m.started = false
+			m.SetState(statePaused)
 		case jobDisable:
-			m.schedule = false
-			m.isDisabled = true
-			m.started = false
+			m.SetState(stateDisabled)
 			return nil
 		case jobRestart:
-			m.schedule = true
-			m.isDisabled = false
-			m.started = true
+			m.SetState(stateReady)
 		case jobStart:
-			m.schedule = true
-			m.isDisabled = false
-			m.started = true
+			m.SetState(stateReady)
 		default:
 			// TODO
 			return nil

worker/worker.go

@@ -186,32 +186,24 @@ func (w *Worker) makeHTTPServer() {
 		// if job disabled, start them first
 		switch cmd.Cmd {
 		case CmdStart, CmdRestart:
-			if job.isDisabled {
+			if job.State() == stateDisabled {
 				go job.Run(w.managerChan, w.semaphore)
 			}
 		}
 		switch cmd.Cmd {
 		case CmdStart:
-			job.schedule = true
-			job.isDisabled = false
 			job.ctrlChan <- jobStart
 		case CmdRestart:
-			job.schedule = true
-			job.isDisabled = false
 			job.ctrlChan <- jobRestart
 		case CmdStop:
 			// if job is disabled, no goroutine would be there
 			// receiving this signal
-			if !job.isDisabled {
-				job.schedule = false
-				job.isDisabled = false
+			if job.State() != stateDisabled {
 				w.schedule.Remove(job.Name())
 				job.ctrlChan <- jobStop
 			}
 		case CmdDisable:
-			if !job.isDisabled {
-				job.schedule = false
-				job.isDisabled = true
+			if job.State() != stateDisabled {
 				w.schedule.Remove(job.Name())
 				job.ctrlChan <- jobDisable
 				<-job.disabled
@@ -270,15 +262,15 @@ func (w *Worker) runSchedule() {
 		if job, ok := w.jobs[m.Name]; ok {
 			delete(unset, m.Name)
 			switch m.Status {
-			case Paused:
-				go job.Run(w.managerChan, w.semaphore)
-				job.schedule = false
-				continue
 			case Disabled:
-				job.schedule = false
-				job.isDisabled = true
+				job.SetState(stateDisabled)
+				continue
+			case Paused:
+				job.SetState(statePaused)
+				go job.Run(w.managerChan, w.semaphore)
 				continue
 			default:
+				job.SetState(stateReady)
 				go job.Run(w.managerChan, w.semaphore)
 				stime := m.LastUpdate.Add(job.provider.Interval())
 				logger.Debug("Scheduling job %s @%s", job.Name(), stime.Format("2006-01-02 15:04:05"))
@@ -286,8 +278,12 @@ func (w *Worker) runSchedule() {
 			}
 		}
 	}
+	// some new jobs may be added
+	// which does not exist in the
+	// manager's mirror list
 	for name := range unset {
 		job := w.jobs[name]
+		job.SetState(stateReady)
 		go job.Run(w.managerChan, w.semaphore)
 		w.schedule.AddJob(time.Now(), job)
 	}
@@ -297,13 +293,19 @@ func (w *Worker) runSchedule() {
 		case jobMsg := <-w.managerChan:
 			// got status update from job
 			job := w.jobs[jobMsg.name]
-			if !job.schedule {
-				logger.Info("Job %s disabled/paused, skip adding new schedule", jobMsg.name)
+			if job.State() != stateReady {
+				logger.Info("Job %s state is not ready, skip adding new schedule", jobMsg.name)
 				continue
 			}
 
+			// syncing status is only meaningful when job
+			// is running. If it's paused or disabled
+			// a sync failure signal would be emitted
+			// which needs to be ignored
 			w.updateStatus(jobMsg)
 
+			// only successful or the final failure msg
+			// can trigger scheduling
 			if jobMsg.schedule {
 				schedTime := time.Now().Add(job.provider.Interval())
 				logger.Info(