Fix issue with feature flags where default value may not be honored

CHANGELOG.md

@@ -111,6 +111,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Removed
 
 ### Fixed
+- Fix issue with feature flags where default value may not be honored ([#12849](https://github.com/opensearch-project/OpenSearch/pull/12849))
 
 ### Security
 

server/src/main/java/org/opensearch/common/util/FeatureFlags.java

@@ -65,10 +65,44 @@ public class FeatureFlags {
      */
     public static final String PLUGGABLE_CACHE = "opensearch.experimental.feature.pluggable.caching.enabled";
 
+    public static final Setting<Boolean> REMOTE_STORE_MIGRATION_EXPERIMENTAL_SETTING = Setting.boolSetting(
+        REMOTE_STORE_MIGRATION_EXPERIMENTAL,
+        false,
+        Property.NodeScope
+    );
+
+    public static final Setting<Boolean> EXTENSIONS_SETTING = Setting.boolSetting(EXTENSIONS, false, Property.NodeScope);
+
+    public static final Setting<Boolean> IDENTITY_SETTING = Setting.boolSetting(IDENTITY, false, Property.NodeScope);
+
+    public static final Setting<Boolean> TELEMETRY_SETTING = Setting.boolSetting(TELEMETRY, false, Property.NodeScope);
+
+    public static final Setting<Boolean> DATETIME_FORMATTER_CACHING_SETTING = Setting.boolSetting(
+        DATETIME_FORMATTER_CACHING,
+        true,
+        Property.NodeScope
+    );
+
+    public static final Setting<Boolean> WRITEABLE_REMOTE_INDEX_SETTING = Setting.boolSetting(
+        WRITEABLE_REMOTE_INDEX,
+        false,
+        Property.NodeScope
+    );
+
+    public static final Setting<Boolean> PLUGGABLE_CACHE_SETTING = Setting.boolSetting(PLUGGABLE_CACHE, false, Property.NodeScope);
+
     /**
      * Should store the settings from opensearch.yml.
      */
-    private static Settings settings;
+    private static Settings settings = Settings.builder()
+        .put(REMOTE_STORE_MIGRATION_EXPERIMENTAL_SETTING.getKey(), REMOTE_STORE_MIGRATION_EXPERIMENTAL_SETTING.getDefault(Settings.EMPTY))
+        .put(EXTENSIONS_SETTING.getKey(), EXTENSIONS_SETTING.getDefault(Settings.EMPTY))
+        .put(IDENTITY_SETTING.getKey(), IDENTITY_SETTING.getDefault(Settings.EMPTY))
+        .put(TELEMETRY_SETTING.getKey(), TELEMETRY_SETTING.getDefault(Settings.EMPTY))
+        .put(DATETIME_FORMATTER_CACHING_SETTING.getKey(), DATETIME_FORMATTER_CACHING_SETTING.getDefault(Settings.EMPTY))
+        .put(WRITEABLE_REMOTE_INDEX_SETTING.getKey(), WRITEABLE_REMOTE_INDEX_SETTING.getDefault(Settings.EMPTY))
+        .put(PLUGGABLE_CACHE_SETTING.getKey(), PLUGGABLE_CACHE_SETTING.getDefault(Settings.EMPTY))
+        .build();;
 
     /**
      * This method is responsible to map settings from opensearch.yml to local stored
@@ -103,30 +137,4 @@ public static boolean isEnabled(Setting<Boolean> featureFlag) {
             return featureFlag.getDefault(Settings.EMPTY);
         }
     }
-
-    public static final Setting<Boolean> REMOTE_STORE_MIGRATION_EXPERIMENTAL_SETTING = Setting.boolSetting(
-        REMOTE_STORE_MIGRATION_EXPERIMENTAL,
-        false,
-        Property.NodeScope
-    );
-
-    public static final Setting<Boolean> EXTENSIONS_SETTING = Setting.boolSetting(EXTENSIONS, false, Property.NodeScope);
-
-    public static final Setting<Boolean> IDENTITY_SETTING = Setting.boolSetting(IDENTITY, false, Property.NodeScope);
-
-    public static final Setting<Boolean> TELEMETRY_SETTING = Setting.boolSetting(TELEMETRY, false, Property.NodeScope);
-
-    public static final Setting<Boolean> DATETIME_FORMATTER_CACHING_SETTING = Setting.boolSetting(
-        DATETIME_FORMATTER_CACHING,
-        true,
-        Property.NodeScope
-    );
-
-    public static final Setting<Boolean> WRITEABLE_REMOTE_INDEX_SETTING = Setting.boolSetting(
-        WRITEABLE_REMOTE_INDEX,
-        false,
-        Property.NodeScope
-    );
-
-    public static final Setting<Boolean> PLUGGABLE_CACHE_SETTING = Setting.boolSetting(PLUGGABLE_CACHE, false, Property.NodeScope);
 }

server/src/test/java/org/opensearch/common/util/FeatureFlagTests.java

@@ -11,6 +11,8 @@
 import org.opensearch.test.FeatureFlagSetter;
 import org.opensearch.test.OpenSearchTestCase;
 
+import static org.opensearch.common.util.FeatureFlags.DATETIME_FORMATTER_CACHING;
+
 public class FeatureFlagTests extends OpenSearchTestCase {
 
     private final String FLAG_PREFIX = "opensearch.experimental.feature.";
@@ -33,4 +35,10 @@ public void testNonBooleanFeatureFlag() {
         assertNotNull(System.getProperty(javaVersionProperty));
         assertFalse(FeatureFlags.isEnabled(javaVersionProperty));
     }
+
+    public void testBooleanFeatureFlagWithDefaultSetToTrue() {
+        final String testFlag = DATETIME_FORMATTER_CACHING;
+        assertNotNull(testFlag);
+        assertTrue(FeatureFlags.isEnabled(testFlag));
+    }
 }