[ASCII-1249] Do not trigger config notification if the value is the s…

…ame (#23383)

* feat: do not trigger config notification if the value is the same

* fix: use proper type in test

comp/metadata/inventoryagent/inventoryagentimpl/inventoryagent_test.go

@@ -261,7 +261,7 @@ func TestConfigRefresh(t *testing.T) {
 	ia := getTestInventoryPayload(t, nil, nil)
 
 	assert.False(t, ia.RefreshTriggered())
-	pkgconfig.Datadog.Set("inventories_max_interval", 10*time.Minute, pkgconfigmodel.SourceAgentRuntime)
+	pkgconfig.Datadog.Set("inventories_max_interval", 10*60, pkgconfigmodel.SourceAgentRuntime)
 	assert.True(t, ia.RefreshTriggered())
 }
 

pkg/config/model/viper.go

@@ -9,6 +9,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"reflect"
 	"strconv"
 	"strings"
 	"sync"
@@ -75,8 +76,9 @@ type safeConfig struct {
 	configEnvVars map[string]struct{}
 }
 
-// OnUpdate adds a callback to the list receivers to be called each time a value is change in the configuration
+// OnUpdate adds a callback to the list receivers to be called each time a value is changed in the configuration
 // by a call to the 'Set' method.
+// Callbacks are only called if the value is effectively changed.
 func (c *safeConfig) OnUpdate(callback NotificationReceiver) {
 	c.Lock()
 	defer c.Unlock()
@@ -93,9 +95,14 @@ func (c *safeConfig) Set(key string, value interface{}, source Source) {
 	// modify the config then release the lock to avoid deadlocks
 	var receivers []NotificationReceiver
 	c.Lock()
+	previousValue := c.Viper.Get(key)
 	c.configSources[source].Set(key, value)
 	c.mergeViperInstances(key)
-	receivers = slices.Clone(c.notificationReceivers)
+	newValue := c.Viper.Get(key)
+	if !reflect.DeepEqual(previousValue, newValue) {
+		// if the value has not changed, do not duplicate the slice so that no callback is called
+		receivers = slices.Clone(c.notificationReceivers)
+	}
 	c.Unlock()
 
 	// notifying all receiver about the updated setting

pkg/config/model/viper_test.go

@@ -332,3 +332,17 @@ func TestNotification(t *testing.T) {
 	assert.Equal(t, []string{"foo", "foo", "foo2"}, updatedKeyCB1)
 	assert.Equal(t, []string{"foo", "foo2"}, updatedKeyCB2)
 }
+
+func TestNotificationNoChange(t *testing.T) {
+	config := NewConfig("test", "DD", strings.NewReplacer(".", "_"))
+
+	updatedKeyCB1 := []string{}
+
+	config.OnUpdate(func(key string) { updatedKeyCB1 = append(updatedKeyCB1, key) })
+
+	config.Set("foo", "bar", SourceFile)
+	assert.Equal(t, []string{"foo"}, updatedKeyCB1)
+
+	config.Set("foo", "bar", SourceFile)
+	assert.Equal(t, []string{"foo"}, updatedKeyCB1)
+}