libbeat/publisher/pipeline: fix Client.Close (elastic#20125)

Set the "closing" variable to true, not false,
upon signalling the waiter to close.

(cherry picked from commit e7b42d8)

libbeat/publisher/pipeline/client.go

@@ -271,7 +271,7 @@ func (w *clientCloseWaiter) signalClose() {
 		return
 	}
 
-	w.closing.Store(false)
+	w.closing.Store(true)
 	if w.events.Load() == 0 {
 		w.finishClose()
 		return

libbeat/publisher/pipeline/client_test.go

@@ -21,11 +21,14 @@ import (
 	"context"
 	"sync"
 	"testing"
+	"time"
 
 	"github.com/elastic/beats/v7/libbeat/beat"
 	"github.com/elastic/beats/v7/libbeat/logp"
 	"github.com/elastic/beats/v7/libbeat/outputs"
+	"github.com/elastic/beats/v7/libbeat/publisher"
 	"github.com/elastic/beats/v7/libbeat/publisher/queue"
+	"github.com/elastic/beats/v7/libbeat/publisher/queue/memqueue"
 	"github.com/elastic/beats/v7/libbeat/tests/resources"
 )
 
@@ -113,3 +116,92 @@ func TestClient(t *testing.T) {
 		}
 	})
 }
+
+func TestClientWaitClose(t *testing.T) {
+	routinesChecker := resources.NewGoroutinesChecker()
+	defer routinesChecker.Check(t)
+
+	makePipeline := func(settings Settings, qu queue.Queue) *Pipeline {
+		p, err := New(beat.Info{},
+			Monitors{},
+			func(queue.ACKListener) (queue.Queue, error) { return qu, nil },
+			outputs.Group{},
+			settings,
+		)
+		if err != nil {
+			panic(err)
+		}
+
+		return p
+	}
+	if testing.Verbose() {
+		logp.TestingSetup()
+	}
+
+	q := memqueue.NewQueue(logp.L(), memqueue.Settings{Events: 1})
+	pipeline := makePipeline(Settings{}, q)
+	defer pipeline.Close()
+
+	t.Run("WaitClose blocks", func(t *testing.T) {
+		client, err := pipeline.ConnectWith(beat.ClientConfig{
+			WaitClose: 500 * time.Millisecond,
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer client.Close()
+
+		// Send an event which never gets acknowledged.
+		client.Publish(beat.Event{})
+
+		closed := make(chan struct{})
+		go func() {
+			defer close(closed)
+			client.Close()
+		}()
+
+		select {
+		case <-closed:
+			t.Fatal("expected Close to wait for event acknowledgement")
+		case <-time.After(100 * time.Millisecond):
+		}
+
+		select {
+		case <-closed:
+		case <-time.After(10 * time.Second):
+			t.Fatal("expected Close to stop waiting after WaitClose elapses")
+		}
+	})
+
+	t.Run("ACKing events unblocks WaitClose", func(t *testing.T) {
+		client, err := pipeline.ConnectWith(beat.ClientConfig{
+			WaitClose: time.Minute,
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer client.Close()
+
+		// Send an event which gets acknowledged immediately.
+		client.Publish(beat.Event{})
+		output := newMockClient(func(batch publisher.Batch) error {
+			batch.ACK()
+			return nil
+		})
+		defer output.Close()
+		pipeline.output.Set(outputs.Group{Clients: []outputs.Client{output}})
+		defer pipeline.output.Set(outputs.Group{})
+
+		closed := make(chan struct{})
+		go func() {
+			defer close(closed)
+			client.Close()
+		}()
+
+		select {
+		case <-closed:
+		case <-time.After(10 * time.Second):
+			t.Fatal("expected Close to stop waiting after event acknowledgement")
+		}
+	})
+}