raft: block Stop() on n.done, support idempotency

raft/node.go

@@ -210,8 +210,15 @@ func newNode() node {
 }
 
 func (n *node) Stop() {
-	n.stop <- struct{}{}
-	<-n.stop
+	select {
+	case n.stop <- struct{}{}:
+		// Not already stopped, so trigger it
+	case <-n.done:
+		// Node has already been stopped - no need to do anything
+		return
+	}
+	// Block until the stop has been acknowledged by run()
+	<-n.done
 }
 
 func (n *node) run(r *raft) {
@@ -306,7 +313,6 @@ func (n *node) run(r *raft) {
 			r.raftLog.stableTo(prevLastUnstablei)
 			advancec = nil
 		case <-n.stop:
-			n.stop <- struct{}{}
 			close(n.done)
 			return
 		}

raft/node_test.go

@@ -141,7 +141,7 @@ func TestBlockProposal(t *testing.T) {
 }
 
 // TestNodeTick ensures that node.Tick() will increase the
-// elapsed of the underly raft state machine.
+// elapsed of the underlying raft state machine.
 func TestNodeTick(t *testing.T) {
 	n := newNode()
 	r := newRaft(1, []uint64{1}, 10, 1)
@@ -154,6 +154,40 @@ func TestNodeTick(t *testing.T) {
 	}
 }
 
+// TestNodeStop ensures that node.Stop() blocks until the node has stopped
+// processing, and that it is idempotent
+func TestNodeStop(t *testing.T) {
+	n := newNode()
+	r := newRaft(1, []uint64{1}, 10, 1)
+	donec := make(chan struct{})
+
+	go func() {
+		n.run(r)
+		close(donec)
+	}()
+
+	elapsed := r.elapsed
+	n.Tick()
+	n.Stop()
+
+	select {
+	case <-donec:
+	case <-time.After(time.Second):
+		t.Fatalf("timed out waiting for node to stop!")
+	}
+
+	if r.elapsed != elapsed+1 {
+		t.Errorf("elapsed = %d, want %d", r.elapsed, elapsed+1)
+	}
+	// Further ticks should have no effect, the node is stopped.
+	n.Tick()
+	if r.elapsed != elapsed+1 {
+		t.Errorf("elapsed = %d, want %d", r.elapsed, elapsed+1)
+	}
+	// Subsequent Stops should have no effect.
+	n.Stop()
+}
+
 func TestReadyContainUpdates(t *testing.T) {
 	tests := []struct {
 		rd       Ready