From 86c4ac0372b95fde55cb655024807508120ad5cd Mon Sep 17 00:00:00 2001
From: Blake Rouse <blake.rouse@elastic.co>
Date: Wed, 22 Sep 2021 10:07:20 -0400
Subject: [PATCH] [Elastic Agent] Fix lazy acker to only add new actions to the
 batch (#27981)

* Fix lazy acker.

* Add changelog.

(cherry picked from commit bdec63a5f1d6d834ad7e4db56b9168e448e82161)
---
 x-pack/elastic-agent/CHANGELOG.next.asciidoc       |  1 +
 .../pkg/fleetapi/acker/lazy/lazy_acker.go          | 14 ++++++++++++--
 .../pkg/fleetapi/acker/lazy/lazy_acker_test.go     |  9 +++++++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/x-pack/elastic-agent/CHANGELOG.next.asciidoc b/x-pack/elastic-agent/CHANGELOG.next.asciidoc
index 52bea97fc46..1c19af428bb 100644
--- a/x-pack/elastic-agent/CHANGELOG.next.asciidoc
+++ b/x-pack/elastic-agent/CHANGELOG.next.asciidoc
@@ -87,6 +87,7 @@
 - Add "_monitoring" suffix to monitoring instance names to remove ambiguity with the status command. {issue}25449[25449]
 - Ignore ErrNotExists when fixing permissions. {issue}27836[27836] {pull}27846[27846]
 - Snapshot artifact lookup will use agent.download proxy settings. {issue}27903[27903] {pull}27904[27904]
+- Fix lazy acker to only add new actions to the batch. {pull}27981[27981]
 
 ==== New features
 
diff --git a/x-pack/elastic-agent/pkg/fleetapi/acker/lazy/lazy_acker.go b/x-pack/elastic-agent/pkg/fleetapi/acker/lazy/lazy_acker.go
index 39f6fb5cd30..c48ac004233 100644
--- a/x-pack/elastic-agent/pkg/fleetapi/acker/lazy/lazy_acker.go
+++ b/x-pack/elastic-agent/pkg/fleetapi/acker/lazy/lazy_acker.go
@@ -37,8 +37,7 @@ func NewAcker(baseAcker batchAcker, log *logger.Logger) *Acker {
 
 // Ack acknowledges action.
 func (f *Acker) Ack(ctx context.Context, action fleetapi.Action) error {
-	f.queue = append(f.queue, action)
-	f.log.Debugf("appending action with id '%s' to the queue", action.ID())
+	f.enqueue(action)
 
 	if _, isAckForced := action.(ackForcer); isAckForced {
 		return f.Commit(ctx)
@@ -58,3 +57,14 @@ func (f *Acker) Commit(ctx context.Context) error {
 	f.queue = make([]fleetapi.Action, 0)
 	return nil
 }
+
+func (f *Acker) enqueue(action fleetapi.Action) {
+	for _, a := range f.queue {
+		if a.ID() == action.ID() {
+			f.log.Debugf("action with id '%s' has already been queued", action.ID())
+			return
+		}
+	}
+	f.queue = append(f.queue, action)
+	f.log.Debugf("appending action with id '%s' to the queue", action.ID())
+}
diff --git a/x-pack/elastic-agent/pkg/fleetapi/acker/lazy/lazy_acker_test.go b/x-pack/elastic-agent/pkg/fleetapi/acker/lazy/lazy_acker_test.go
index 1e34d303bc5..216349b90af 100644
--- a/x-pack/elastic-agent/pkg/fleetapi/acker/lazy/lazy_acker_test.go
+++ b/x-pack/elastic-agent/pkg/fleetapi/acker/lazy/lazy_acker_test.go
@@ -79,12 +79,21 @@ func TestLazyAcker(t *testing.T) {
 	}()
 	c := context.Background()
 
+	if err := lacker.Ack(c, testAction1); err != nil {
+		t.Fatal(err)
+	}
 	if err := lacker.Ack(c, testAction1); err != nil {
 		t.Fatal(err)
 	}
 	if err := lacker.Ack(c, testAction2); err != nil {
 		t.Fatal(err)
 	}
+	if err := lacker.Ack(c, testAction2); err != nil {
+		t.Fatal(err)
+	}
+	if err := lacker.Ack(c, testAction3); err != nil {
+		t.Fatal(err)
+	}
 	if err := lacker.Ack(c, testAction3); err != nil {
 		t.Fatal(err)
 	}