add TaskFail interface

go/master/client.go

@@ -112,6 +112,11 @@ func (c *Client) taskFinished(taskID int) error {
 	return c.conn.Call("Service.TaskFinished", taskID, nil)
 }
 
+// TaskFailed tell the master server as task is failed.
+func (c *Client) taskFailed(taskID TaskID) error {
+	return c.conn.Call("Service.TaskFinished", taskID, nil)
+}
+
 // NextRecord returns next record in the dataset.
 //
 // NextRecord will block until the next record is available. It is

go/master/service.go

@@ -34,27 +34,28 @@ type Chunk struct {
 // Task is the basic unit of data instances assigned to trainers.
 type Task struct {
 	ID     int
+	Epoch  int
 	Chunks []Chunk
 }
 
 type taskEntry struct {
-	Epoch      int
-	NumTimeout int
-	Task       Task
+	Task Task
+	// A task fails if it's timeout or trainer reports it exits unnormally.
+	NumFailure int
 }
 
 type taskQueues struct {
 	Todo    []taskEntry
 	Pending map[int]taskEntry // map from task ID to task entry
 	Done    []taskEntry
-	Failed  []Task
+	Failed  []taskEntry
 }
 
 // Service is the master server service.
 type Service struct {
 	chunksPerTask int
 	timeoutDur    time.Duration
-	timeoutMax    int
+	failureMax    int
 	ready         chan struct{}
 	store         Store
 
@@ -91,11 +92,11 @@ func partition(chunks []Chunk, chunksPerTask int) []taskEntry {
 }
 
 // NewService creates a new service.
-func NewService(store Store, chunksPerTask int, timeoutDur time.Duration, timeoutMax int) (*Service, error) {
+func NewService(store Store, chunksPerTask int, timeoutDur time.Duration, failureMax int) (*Service, error) {
 	s := &Service{}
 	s.chunksPerTask = chunksPerTask
 	s.timeoutDur = timeoutDur
-	s.timeoutMax = timeoutMax
+	s.failureMax = failureMax
 	s.taskQueues = taskQueues{}
 	s.taskQueues.Pending = make(map[int]taskEntry)
 	s.ready = make(chan struct{})
@@ -257,6 +258,34 @@ func (s *Service) SetDataset(globPaths []string, dummy *int) error {
 	return nil
 }
 
+func (s *Service) procFailedTask(t taskEntry, epoch int) {
+	if t.Task.Epoch != epoch {
+		// new epoch, task launched after the
+		// schedule of this timeout check or failed status report.
+		return
+	}
+
+	defer func() {
+		err := s.snapshot()
+		if err != nil {
+			log.Errorln(err)
+		}
+	}()
+
+	delete(s.taskQueues.Pending, t.Task.ID)
+
+	t.NumFailure++
+	if t.NumFailure > s.failureMax {
+		log.Warningf("Task %v failed %d times, discard.", t.Task, t.NumFailure)
+		s.taskQueues.Failed = append(s.taskQueues.Failed, t)
+		return
+	}
+
+	log.Warningf("Task %v failed %d times, discard.", t.Task, t.NumFailure)
+	s.taskQueues.Todo = append(s.taskQueues.Todo, t)
+	return
+}
+
 func (s *Service) checkTimeoutFunc(taskID int, epoch int) func() {
 	return func() {
 		s.mu.Lock()
@@ -267,30 +296,7 @@ func (s *Service) checkTimeoutFunc(taskID int, epoch int) func() {
 			return
 		}
 
-		if t.Epoch != epoch {
-			// new epoch, task launched after the
-			// schedule of this timeout check.
-			return
-		}
-
-		defer func() {
-			err := s.snapshot()
-			if err != nil {
-				log.Errorln(err)
-			}
-		}()
-
-		delete(s.taskQueues.Pending, t.Task.ID)
-
-		t.NumTimeout++
-		if t.NumTimeout > s.timeoutMax {
-			log.Warningf("Task %v timed out %d times, discard.", t.Task, t.NumTimeout)
-			s.taskQueues.Failed = append(s.taskQueues.Failed, t.Task)
-			return
-		}
-
-		log.Warningf("Task %v timed out %d times, retry.", t.Task, t.NumTimeout)
-		s.taskQueues.Todo = append(s.taskQueues.Todo, t)
+		s.procFailedTask(t, epoch)
 	}
 }
 
@@ -339,7 +345,7 @@ func (s *Service) GetTask(dummy int, task *Task) error {
 	}
 
 	t := s.taskQueues.Todo[0]
-	t.Epoch++
+	t.Task.Epoch++
 	s.taskQueues.Todo = s.taskQueues.Todo[1:]
 	s.taskQueues.Pending[t.Task.ID] = t
 	err := s.snapshot()
@@ -348,9 +354,9 @@ func (s *Service) GetTask(dummy int, task *Task) error {
 	}
 
 	*task = t.Task
-	log.WithFields(s.logFields()).Infof("Task #%d dispatched.", task.ID)
+	log.WithFields(s.logFields()).Infof("Task #%v dispatched.", t)
 
-	time.AfterFunc(s.timeoutDur, s.checkTimeoutFunc(t.Task.ID, t.Epoch))
+	time.AfterFunc(s.timeoutDur, s.checkTimeoutFunc(t.Task.ID, t.Task.Epoch))
 	return nil
 }
 
@@ -371,7 +377,7 @@ func (s *Service) TaskFinished(taskID int, dummy *int) error {
 	}
 
 	// task finished, reset timeout
-	t.NumTimeout = 0
+	t.NumFailure = 0
 	s.taskQueues.Done = append(s.taskQueues.Done, t)
 	delete(s.taskQueues.Pending, taskID)
 
@@ -389,3 +395,29 @@ func (s *Service) TaskFinished(taskID int, dummy *int) error {
 	}
 	return err
 }
+
+// TaskID is a struct which client uses for reports failure.
+type TaskID struct {
+	ID    int
+	Epoch int
+}
+
+// TaskFailed tells the service that a task is failed.
+func (s *Service) TaskFailed(taskID TaskID, dummy *int) error {
+	select {
+	case <-s.ready:
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	t, ok := s.taskQueues.Pending[taskID.ID]
+	if !ok {
+		err := errors.New("pending task not found")
+		log.WithFields(s.logFields()).Warningln("TaskFailed:Pending task #%v not found.", taskID)
+		return err
+	}
+
+	s.procFailedTask(t, taskID.Epoch)
+	return nil
+}