fix according to comments

go/connection/conn.go

@@ -62,6 +62,7 @@ func (c *Conn) Connect(addr string) error {
 			c.waitConn = nil
 		}
 	} else {
+		client.Close()
 		return errors.New("client already set from a concurrent goroutine")
 	}
 

go/master/service.go

@@ -11,10 +11,6 @@ import (
 	"github.com/PaddlePaddle/recordio"
 )
 
-const (
-	targetTaskCount = 300
-)
-
 // Service is the master server service.
 type Service struct {
 	chunksPerTask int
@@ -23,7 +19,7 @@ type Service struct {
 	ready         chan struct{}
 
 	mu         sync.Mutex
-	initBegan  bool
+	initDone   bool
 	taskQueues taskQueues
 }
 
@@ -104,54 +100,35 @@ func (s *Service) snapshot() error {
 	return nil
 }
 
-// SetDataset sets dataset to dispatch for the master server.
-//
-// SetDataset can be call multiple times. But only the first call will
-// be honored.
-func (s *Service) SetDataset(globPaths []string, dummy *int) error {
-	if len(globPaths) == 0 {
-		return errors.New("no dataset specified")
-	}
-
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	if s.initBegan {
-		// SetDataset already called. All trainer will call
-		// SetDataset, but we only handle the first one. Treat
-		// other calls as successful but do nothing.
-		return nil
-	}
-
-	s.initBegan = true
-
+func getChunks(globPaths []string) ([]Chunk, error) {
 	var chunks []Chunk
 	var paths []string
 
 	for _, s := range globPaths {
 		match, err := filepath.Glob(s)
 		if err != nil {
-			panic(err)
+			return nil, err
 		}
 		paths = append(paths, match...)
 	}
 
 	if len(paths) == 0 {
-		return errors.New("no valid datset specified")
+		return nil, errors.New("no valid datset specified")
 	}
 
 	for _, path := range paths {
 		f, err := os.Open(path)
 		if err != nil {
-			panic(err)
+			return nil, err
 		}
 
 		index, err := recordio.LoadIndex(f)
 		if err != nil {
-			return err
+			return nil, err
 		}
 		err = f.Close()
 		if err != nil {
-			return err
+			return nil, err
 		}
 
 		count := index.NumChunks()
@@ -164,14 +141,41 @@ func (s *Service) SetDataset(globPaths []string, dummy *int) error {
 		}
 	}
 
+	return chunks, nil
+}
+
+// SetDataset sets dataset to dispatch for the master server.
+//
+// SetDataset can be call multiple times. But only the first call will
+// be honored.
+func (s *Service) SetDataset(globPaths []string, dummy *int) error {
+	if len(globPaths) == 0 {
+		return errors.New("no dataset specified")
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.initDone {
+		// Already initialized. All trainer will call
+		// SetDataset, but we only handle the first one. Treat
+		// other calls as successful but do nothing.
+		return nil
+	}
+
+	chunks, err := getChunks(globPaths)
+	if err != nil {
+		return err
+	}
+
 	s.taskQueues.Todo = partition(chunks, s.chunksPerTask)
 
-	err := s.snapshot()
+	err = s.snapshot()
 	if err != nil {
 		return err
 	}
 
 	close(s.ready)
+	s.initDone = true
 	return nil
 }
 
@@ -193,7 +197,7 @@ func (s *Service) GetTask(dummy int, task *Task) error {
 			// TODO(helin): client need to retry in this
 			// error case. Gotcha: RPC client can't
 			// compare returned error with predefined
-			// erros like io.EOF. Because interface don't
+			// errors like io.EOF. Because interface don't
 			// have same dynamic value when in different
 			// process.
 			return errors.New("no more available task")