Benchmark for pkg/pubsub package

Signed-off-by: Alexander Morozov <lk4d4@docker.com>

pkg/pubsub/publisher_test.go

@@ -1,6 +1,7 @@
 package pubsub
 
 import (
+	"fmt"
 	"testing"
 	"time"
 )
@@ -61,3 +62,61 @@ func TestClosePublisher(t *testing.T) {
 		}
 	}
 }
+
+const sampleText = "test"
+
+type testSubscriber struct {
+	dataCh chan interface{}
+	ch     chan error
+}
+
+func (s *testSubscriber) Wait() error {
+	return <-s.ch
+}
+
+func newTestSubscriber(p *Publisher) *testSubscriber {
+	ts := &testSubscriber{
+		dataCh: p.Subscribe(),
+		ch:     make(chan error),
+	}
+	go func() {
+		for data := range ts.dataCh {
+			s, ok := data.(string)
+			if !ok {
+				ts.ch <- fmt.Errorf("Unexpected type %T", data)
+				break
+			}
+			if s != sampleText {
+				ts.ch <- fmt.Errorf("Unexpected text %s", s)
+				break
+			}
+		}
+		close(ts.ch)
+	}()
+	return ts
+}
+
+func BenchmarkPubSub(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		b.StopTimer()
+		p := NewPublisher(0, 1024)
+		var subs [](*testSubscriber)
+		for j := 0; j < 50; j++ {
+			subs = append(subs, newTestSubscriber(p))
+		}
+		b.StartTimer()
+		for j := 0; j < 1000; j++ {
+			p.Publish(sampleText)
+		}
+		time.AfterFunc(1*time.Second, func() {
+			for _, s := range subs {
+				p.Evict(s.dataCh)
+			}
+		})
+		for _, s := range subs {
+			if err := s.Wait(); err != nil {
+				b.Fatal(err)
+			}
+		}
+	}
+}