[HA Agent] Log leader state change (DataDog#31734)

comp/haagent/impl/haagent.go

@@ -44,10 +44,17 @@ func (h *haAgentImpl) IsLeader() bool {
 func (h *haAgentImpl) SetLeader(leaderAgentHostname string) {
 	agentHostname, err := hostname.Get(context.TODO())
 	if err != nil {
-		h.log.Warnf("Error getting the hostname: %v", err)
+		h.log.Warnf("error getting the hostname: %v", err)
 		return
 	}
-	h.isLeader.Store(agentHostname == leaderAgentHostname)
+	newIsLeader := agentHostname == leaderAgentHostname
+	prevIsLeader := h.isLeader.Load()
+	if newIsLeader != prevIsLeader {
+		h.log.Infof("agent role switched from %s to %s", leaderStateToRole(prevIsLeader), leaderStateToRole(newIsLeader))
+		h.isLeader.Store(newIsLeader)
+	} else {
+		h.log.Debugf("agent role not changed (current role: %s)", leaderStateToRole(prevIsLeader))
+	}
 }
 
 // ShouldRunIntegration return true if the agent integrations should to run.

comp/haagent/impl/utils.go

@@ -0,0 +1,13 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2024-present Datadog, Inc.
+
+package haagentimpl
+
+func leaderStateToRole(isLeader bool) string {
+	if isLeader {
+		return "leader"
+	}
+	return "follower"
+}

comp/haagent/impl/utils_test.go

@@ -0,0 +1,17 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2024-present Datadog, Inc.
+
+package haagentimpl
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_leaderStatusToRole(t *testing.T) {
+	assert.Equal(t, "leader", leaderStateToRole(true))
+	assert.Equal(t, "follower", leaderStateToRole(false))
+}