lib/events: Add logging/receiving benchmark

lib/events/events_test.go

@@ -185,5 +185,55 @@ func TestBufferedSub(t *testing.T) {
 			recv = ev.ID
 		}
 	}
-
+}
+
+func BenchmarkBufferedSub(b *testing.B) {
+	l := events.NewLogger()
+
+	s := l.Subscribe(events.AllEvents)
+	defer l.Unsubscribe(s)
+	bufferSize := events.BufferSize
+	bs := events.NewBufferedSubscription(s, bufferSize)
+
+	// The coord channel paces the sender according to the receiver,
+	// ensuring that no events are dropped. The benchmark measures sending +
+	// receiving + synchronization overhead.
+
+	coord := make(chan struct{}, bufferSize)
+	for i := 0; i < bufferSize-1; i++ {
+		coord <- struct{}{}
+	}
+
+	// Receive the events
+	done := make(chan struct{})
+	go func() {
+		defer close(done)
+		recv := 0
+		var evs []events.Event
+		for i := 0; i < b.N; {
+			evs = bs.Since(recv, evs[:0])
+			for _, ev := range evs {
+				if ev.ID != recv+1 {
+					b.Fatal("skipped event", ev.ID, recv)
+				}
+				recv = ev.ID
+				coord <- struct{}{}
+			}
+			i += len(evs)
+		}
+	}()
+
+	// Send the events
+	eventData := map[string]string{
+		"foo":   "bar",
+		"other": "data",
+		"and":   "something else",
+	}
+	for i := 0; i < b.N; i++ {
+		l.Log(events.DeviceConnected, eventData)
+		<-coord
+	}
+
+	<-done
+	b.ReportAllocs()
 }