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/batching_channel_test.go

@@ -0,0 +1,45 @@
+package channels
+
+import "testing"
+
+func testBatches(t *testing.T, ch Channel) {
+	go func() {
+		for i := 0; i < 1000; i++ {
+			ch.In() <- i
+		}
+		ch.Close()
+	}()
+
+	i := 0
+	for val := range ch.Out() {
+		for _, elem := range val.([]interface{}) {
+			if i != elem.(int) {
+				t.Fatal("batching channel expected", i, "but got", elem.(int))
+			}
+			i++
+		}
+	}
+}
+
+func TestBatchingChannel(t *testing.T) {
+	ch := NewBatchingChannel(Infinity)
+	testBatches(t, ch)
+
+	ch = NewBatchingChannel(2)
+	testBatches(t, ch)
+
+	ch = NewBatchingChannel(1)
+	testChannelConcurrentAccessors(t, "batching channel", ch)
+}
+
+func TestBatchingChannelCap(t *testing.T) {
+	ch := NewBatchingChannel(Infinity)
+	if ch.Cap() != Infinity {
+		t.Error("incorrect capacity on infinite channel")
+	}
+
+	ch = NewBatchingChannel(5)
+	if ch.Cap() != 5 {
+		t.Error("incorrect capacity on infinite channel")
+	}
+}