feat: Allow deactivating of polling by setting a negative polling (#3205)

Signed-off-by: Thomas Poignant <thomas.poignant@gofeatureflag.org>

Author: thomaspoignant

feature_flag.go

@@ -61,10 +61,7 @@ func New(config Config) (*GoFeatureFlag, error) {
 	case config.PollingInterval == 0:
 		// The default value for the poll interval is 60 seconds
 		config.PollingInterval = 60 * time.Second
-	case config.PollingInterval < 0:
-		// Check that value is not negative
-		return nil, fmt.Errorf("%d is not a valid PollingInterval value, it need to be > 0", config.PollingInterval)
-	case config.PollingInterval < time.Second:
+	case config.PollingInterval > 0 && config.PollingInterval < time.Second:
 		// the minimum value for the polling policy is 1 second
 		config.PollingInterval = time.Second
 	default:
@@ -89,7 +86,6 @@ func New(config Config) (*GoFeatureFlag, error) {
 		notifiers = append(notifiers, &logsnotifier.Notifier{Logger: config.internalLogger})
 
 		notificationService := cache.NewNotificationService(notifiers)
-		goFF.bgUpdater = newBackgroundUpdater(config.PollingInterval, config.EnablePollingJitter)
 		goFF.cache = cache.New(notificationService, config.PersistentFlagConfigurationFile, config.internalLogger)
 
 		retrievers, err := config.GetRetrievers()
@@ -120,7 +116,10 @@ func New(config Config) (*GoFeatureFlag, error) {
 			}
 		}
 
-		go goFF.startFlagUpdaterDaemon()
+		if config.PollingInterval > 0 {
+			goFF.bgUpdater = newBackgroundUpdater(config.PollingInterval, config.EnablePollingJitter)
+			go goFF.startFlagUpdaterDaemon()
+		}
 
 		exporters := goFF.config.GetDataExporters()
 		if len(exporters) > 0 {

feature_flag_test.go

@@ -75,15 +75,6 @@ func TestMultipleRetrieversWithOverrideFlag(t *testing.T) {
 	assert.NotEqual(t, flag.ErrorCodeFlagNotFound, flagRes2.ErrorCode)
 }
 
-func TestStartWithNegativeInterval(t *testing.T) {
-	_, err := ffclient.New(ffclient.Config{
-		PollingInterval: -60 * time.Second,
-		Retriever:       &fileretriever.Retriever{Path: "testdata/flag-config.yaml"},
-		LeveledLogger:   slog.Default(),
-	})
-	assert.Error(t, err)
-}
-
 func TestStartWithMinInterval(t *testing.T) {
 	_, err := ffclient.New(ffclient.Config{
 		PollingInterval: 2,
@@ -743,3 +734,39 @@ func Test_DisableNotifierOnInit(t *testing.T) {
 		})
 	}
 }
+
+func TestStartWithNegativeIntervalToDisablePolling(t *testing.T) {
+	content, err := os.ReadFile("testdata/flag-config.yaml")
+	assert.NoError(t, err)
+
+	// copy of the file
+	tempFile, err := os.CreateTemp("", "")
+	assert.NoError(t, err)
+	defer func() { _ = os.Remove(tempFile.Name()) }()
+	err = os.WriteFile(tempFile.Name(), content, os.ModePerm)
+	assert.NoError(t, err)
+
+	goff, err := ffclient.New(ffclient.Config{
+		PollingInterval: -1 * time.Second,
+		Retriever:       &fileretriever.Retriever{Path: tempFile.Name()},
+		LeveledLogger:   slog.Default(),
+	})
+	assert.NoError(t, err)
+
+	cacheRefresh := goff.GetCacheRefreshDate()
+
+	// modify the file to trigger a refresh
+	newContent, err := os.ReadFile("testdata/flag-config-2nd-file.yaml")
+	assert.NoError(t, err)
+	err = os.WriteFile(tempFile.Name(), newContent, os.ModePerm)
+	assert.NoError(t, err)
+
+	// wait to be sure we give time to the goroutine to refresh the cache
+	time.Sleep(2 * time.Second)
+
+	assert.Equal(t, cacheRefresh, goff.GetCacheRefreshDate())
+
+	// we force a refresh to check if the cache is refreshed
+	goff.ForceRefresh()
+	assert.NotEqual(t, cacheRefresh, goff.GetCacheRefreshDate())
+}