Use a ring channel to avoid blocking write of events (#2082)

* Use a ring channel to avoid blocking write of events

* Add eapache/channels dependency

vendor/github.com/eapache/channels/native_channel_test.go

@@ -0,0 +1,58 @@
+package channels
+
+import "testing"
+
+func TestNativeChannels(t *testing.T) {
+	var ch Channel
+
+	ch = NewNativeChannel(None)
+	testChannel(t, "bufferless native channel", ch)
+
+	ch = NewNativeChannel(None)
+	testChannelPair(t, "bufferless native channel", ch, ch)
+
+	ch = NewNativeChannel(5)
+	testChannel(t, "5-buffer native channel", ch)
+
+	ch = NewNativeChannel(5)
+	testChannelPair(t, "5-buffer native channel", ch, ch)
+
+	ch = NewNativeChannel(None)
+	testChannelConcurrentAccessors(t, "native channel", ch)
+}
+
+func TestNativeInOutChannels(t *testing.T) {
+	ch1 := make(chan interface{})
+	ch2 := make(chan interface{})
+
+	Pipe(NativeOutChannel(ch1), NativeInChannel(ch2))
+	NativeInChannel(ch1).Close()
+}
+
+func TestDeadChannel(t *testing.T) {
+	ch := NewDeadChannel()
+
+	if ch.Len() != 0 {
+		t.Error("dead channel length not 0")
+	}
+	if ch.Cap() != 0 {
+		t.Error("dead channel cap not 0")
+	}
+
+	select {
+	case <-ch.Out():
+		t.Error("read from a dead channel")
+	default:
+	}
+
+	select {
+	case ch.In() <- nil:
+		t.Error("wrote to a dead channel")
+	default:
+	}
+
+	ch.Close()
+
+	ch = NewDeadChannel()
+	testChannelConcurrentAccessors(t, "dead channel", ch)
+}