simplify tracker, prevent send to closed chan

pkg/snapshot/service.go

@@ -109,8 +109,7 @@ func (s *Service) CreateSnapshot(params SnapshotParams) error {
 	}
 	headerID := header.Hash().String()
 	s.tracker = newTracker(s.recoveryFile, int(params.Workers))
-	go s.tracker.run()
-	go s.tracker.captureSignal()
+	s.tracker.captureSignal()
 
 	log.Infof("after goroutines start")
 

pkg/snapshot/tracker.go

@@ -22,7 +22,11 @@ type trackedIter struct {
 func (it *trackedIter) Next(descend bool) bool {
 	ret := it.NodeIterator.Next(descend)
 	if !ret {
+		if it.tracker.running {
 			it.tracker.stopChan <- it
+		} else {
+			log.Errorf("iterator stopped after tracker halted: path=%x", it.Path())
+		}
 	}
 	return ret
 }
@@ -34,9 +38,7 @@ type iteratorTracker struct {
 	stopChan  chan *trackedIter
 	started   map[*trackedIter]struct{}
 	stopped   []*trackedIter
-
-	haltChan chan struct{}
-	done     chan struct{}
+	running   bool
 }
 
 func newTracker(file string, buf int) iteratorTracker {
@@ -45,8 +47,7 @@ func newTracker(file string, buf int) iteratorTracker {
 		startChan:    make(chan *trackedIter, buf),
 		stopChan:     make(chan *trackedIter, buf),
 		started:      map[*trackedIter]struct{}{},
-		haltChan:     make(chan struct{}),
-		done:         make(chan struct{}),
+		running:      true,
 	}
 }
 
@@ -62,23 +63,7 @@ func (tr *iteratorTracker) captureSignal() {
 	}()
 }
 
-// listens for starts/stops and manages current state
-func (tr *iteratorTracker) run() {
-loop:
-	for {
-		select {
-		case start := <-tr.startChan:
-			tr.started[start] = struct{}{}
-		case stop := <-tr.stopChan:
-			tr.stopped = append(tr.stopped, stop)
-		case <-tr.haltChan:
-			break loop
-		default:
-		}
-	}
-	tr.done <- struct{}{}
-}
-
+// Wraps an iterator in a trackedIter. This should not be called once halts are possible.
 func (tr *iteratorTracker) tracked(it trie.NodeIterator) (ret *trackedIter) {
 	ret = &trackedIter{it, tr}
 	tr.startChan <- ret
@@ -149,8 +134,7 @@ func (tr *iteratorTracker) restore(tree state.Trie) ([]trie.NodeIterator, error)
 }
 
 func (tr *iteratorTracker) haltAndDump() error {
-	tr.haltChan <- struct{}{}
-	<-tr.done
+	tr.running = false
 
 	// drain any pending events
 	close(tr.startChan)