Move calls to FeatureFlag.enabled to class-load time (#125885)

I noticed that we tend to create the flag instance and call this method
everywhere. This doesn't compile the same way as a real boolean constant
unless you're running with `-XX:+TrustFinalNonStaticFields`.
For most of the code spots changed here that's irrelevant but at least
the usage in the mapper parsing code is a little hot and gets a small
speedup from this potentially.
Also we're simply wasting some bytes for the static footprint of ES by
using the `FeatureFlag` indirection instead of just a boolean.

Author: original-brownbear

modules/data-streams/src/test/java/org/elasticsearch/datastreams/mapper/DataStreamTimestampFieldMapperTests.java

@@ -235,11 +235,11 @@ public void testSearchIdleStats() throws InterruptedException {
     }
 
     public void testSearchIdleBoolQueryMatchOneIndex() throws InterruptedException {
-        checkSearchIdleBoolQueryMatchOneIndex(IndexSettings.DOC_VALUES_SKIPPER.isEnabled());
+        checkSearchIdleBoolQueryMatchOneIndex(IndexSettings.DOC_VALUES_SKIPPER);
     }
 
     public void testSearchIdleBoolQueryMatchOneIndexWithDocValuesSkipper() throws InterruptedException {
-        assumeTrue("doc values skipper feature should be enabled", IndexSettings.DOC_VALUES_SKIPPER.isEnabled());
+        assumeTrue("doc values skipper feature should be enabled", IndexSettings.DOC_VALUES_SKIPPER);
         checkSearchIdleBoolQueryMatchOneIndex(false);
     }
 

server/src/internalClusterTest/java/org/elasticsearch/index/shard/SearchIdleIT.java

@@ -71,13 +71,13 @@
 
 public final class DataStream implements SimpleDiffable<DataStream>, ToXContentObject, IndexAbstraction {
 
-    public static final FeatureFlag FAILURE_STORE_FEATURE_FLAG = new FeatureFlag("failure_store");
+    public static final boolean FAILURE_STORE_FEATURE_FLAG = new FeatureFlag("failure_store").isEnabled();
     public static final TransportVersion ADDED_FAILURE_STORE_TRANSPORT_VERSION = TransportVersions.V_8_12_0;
     public static final TransportVersion ADDED_AUTO_SHARDING_EVENT_VERSION = TransportVersions.V_8_14_0;
     public static final TransportVersion ADD_DATA_STREAM_OPTIONS_VERSION = TransportVersions.V_8_16_0;
 
     public static boolean isFailureStoreFeatureFlagEnabled() {
-        return FAILURE_STORE_FEATURE_FLAG.isEnabled();
+        return FAILURE_STORE_FEATURE_FLAG;
     }
 
     public static final String BACKING_INDEX_PREFIX = ".ds-";

server/src/main/java/org/elasticsearch/cluster/metadata/DataStream.java

@@ -234,7 +234,7 @@ public final class IndexScopedSettings extends AbstractScopedSettings {
             )
         );
 
-        if (IndexSettings.DOC_VALUES_SKIPPER.isEnabled()) {
+        if (IndexSettings.DOC_VALUES_SKIPPER) {
             settings.add(IndexSettings.USE_DOC_VALUES_SKIPPER);
         }
         BUILT_IN_INDEX_SETTINGS = Collections.unmodifiableSet(settings);

server/src/main/java/org/elasticsearch/common/settings/IndexScopedSettings.java

@@ -674,7 +674,7 @@ public boolean isES87TSDBCodecEnabled() {
         Property.Final
     );
 
-    public static final FeatureFlag DOC_VALUES_SKIPPER = new FeatureFlag("doc_values_skipper");
+    public static final boolean DOC_VALUES_SKIPPER = new FeatureFlag("doc_values_skipper").isEnabled();
     public static final Setting<Boolean> USE_DOC_VALUES_SKIPPER = Setting.boolSetting(
         "index.mapping.use_doc_values_skipper",
         false,
@@ -1095,7 +1095,7 @@ public IndexSettings(final IndexMetadata indexMetadata, final Settings nodeSetti
         recoverySourceEnabled = RecoverySettings.INDICES_RECOVERY_SOURCE_ENABLED_SETTING.get(nodeSettings);
         recoverySourceSyntheticEnabled = DiscoveryNode.isStateless(nodeSettings) == false
             && scopedSettings.get(RECOVERY_USE_SYNTHETIC_SOURCE_SETTING);
-        useDocValuesSkipper = DOC_VALUES_SKIPPER.isEnabled() && scopedSettings.get(USE_DOC_VALUES_SKIPPER);
+        useDocValuesSkipper = DOC_VALUES_SKIPPER && scopedSettings.get(USE_DOC_VALUES_SKIPPER);
         if (recoverySourceSyntheticEnabled) {
             if (DiscoveryNode.isStateless(settings)) {
                 throw new IllegalArgumentException("synthetic recovery source is only allowed in stateful");

server/src/main/java/org/elasticsearch/index/IndexSettings.java

@@ -31,7 +31,7 @@
  */
 public class CodecService implements CodecProvider {
 
-    public static final FeatureFlag ZSTD_STORED_FIELDS_FEATURE_FLAG = new FeatureFlag("zstd_stored_fields");
+    public static final boolean ZSTD_STORED_FIELDS_FEATURE_FLAG = new FeatureFlag("zstd_stored_fields").isEnabled();
 
     private final Map<String, Codec> codecs;
 
@@ -47,7 +47,7 @@ public CodecService(@Nullable MapperService mapperService, BigArrays bigArrays)
         final var codecs = new HashMap<String, Codec>();
 
         Codec legacyBestSpeedCodec = new LegacyPerFieldMapperCodec(Lucene101Codec.Mode.BEST_SPEED, mapperService, bigArrays);
-        if (ZSTD_STORED_FIELDS_FEATURE_FLAG.isEnabled()) {
+        if (ZSTD_STORED_FIELDS_FEATURE_FLAG) {
             codecs.put(DEFAULT_CODEC, new PerFieldMapperCodec(Zstd814StoredFieldsFormat.Mode.BEST_SPEED, mapperService, bigArrays));
         } else {
             codecs.put(DEFAULT_CODEC, legacyBestSpeedCodec);

server/src/main/java/org/elasticsearch/index/codec/CodecService.java

@@ -48,7 +48,7 @@
 public class ObjectMapper extends Mapper {
     private static final Logger logger = LogManager.getLogger(ObjectMapper.class);
     private static final DeprecationLogger deprecationLogger = DeprecationLogger.getLogger(ObjectMapper.class);
-    public static final FeatureFlag SUB_OBJECTS_AUTO_FEATURE_FLAG = new FeatureFlag("sub_objects_auto");
+    public static final boolean SUB_OBJECTS_AUTO_FEATURE_FLAG = new FeatureFlag("sub_objects_auto").isEnabled();
     static final NodeFeature SUBOBJECTS_FALSE_MAPPING_UPDATE_FIX = new NodeFeature("mapper.subobjects_false_mapping_update_fix");
 
     public static final String CONTENT_TYPE = "object";
@@ -80,7 +80,7 @@ public static Subobjects from(Object node) {
                 if (value.equalsIgnoreCase("false")) {
                     return DISABLED;
                 }
-                if (SUB_OBJECTS_AUTO_FEATURE_FLAG.isEnabled() && value.equalsIgnoreCase("auto")) {
+                if (SUB_OBJECTS_AUTO_FEATURE_FLAG && value.equalsIgnoreCase("auto")) {
                     return AUTO;
                 }
             }

server/src/main/java/org/elasticsearch/index/mapper/ObjectMapper.java

@@ -48,7 +48,7 @@ public void testDefaultCodecLogsdb() {
     }
 
     public void testDefaultCodec() {
-        assumeTrue("Only when zstd_stored_fields feature flag is enabled", CodecService.ZSTD_STORED_FIELDS_FEATURE_FLAG.isEnabled());
+        assumeTrue("Only when zstd_stored_fields feature flag is enabled", CodecService.ZSTD_STORED_FIELDS_FEATURE_FLAG);
 
         var indexService = createIndex("index1");
         var storedFieldsFormat = (Zstd814StoredFieldsFormat) indexService.getShard(0)

server/src/test/java/org/elasticsearch/index/codec/CodecIntegrationTests.java

@@ -47,14 +47,14 @@
 public class CodecTests extends ESTestCase {
 
     public void testResolveDefaultCodecs() throws Exception {
-        assumeTrue("Only when zstd_stored_fields feature flag is enabled", CodecService.ZSTD_STORED_FIELDS_FEATURE_FLAG.isEnabled());
+        assumeTrue("Only when zstd_stored_fields feature flag is enabled", CodecService.ZSTD_STORED_FIELDS_FEATURE_FLAG);
         CodecService codecService = createCodecService();
         assertThat(codecService.codec("default"), instanceOf(PerFieldMapperCodec.class));
         assertThat(codecService.codec("default"), instanceOf(Elasticsearch900Lucene101Codec.class));
     }
 
     public void testDefault() throws Exception {
-        assumeTrue("Only when zstd_stored_fields feature flag is enabled", CodecService.ZSTD_STORED_FIELDS_FEATURE_FLAG.isEnabled());
+        assumeTrue("Only when zstd_stored_fields feature flag is enabled", CodecService.ZSTD_STORED_FIELDS_FEATURE_FLAG);
         Codec codec = createCodecService().codec("default");
         assertEquals(
             "Zstd814StoredFieldsFormat(compressionMode=ZSTD(level=1), chunkSize=14336, maxDocsPerChunk=128, blockShift=10)",

server/src/test/java/org/elasticsearch/index/codec/CodecTests.java

@@ -152,7 +152,7 @@ public void testPostingsFormat() throws IOException {
         MapperService mapperService = createMapperService(fieldMapping(this::minimalMapping));
         CodecService codecService = new CodecService(mapperService, BigArrays.NON_RECYCLING_INSTANCE);
         Codec codec = codecService.codec("default");
-        if (CodecService.ZSTD_STORED_FIELDS_FEATURE_FLAG.isEnabled()) {
+        if (CodecService.ZSTD_STORED_FIELDS_FEATURE_FLAG) {
             assertThat(codec, instanceOf(PerFieldMapperCodec.class));
             assertThat(((PerFieldMapperCodec) codec).getPostingsFormatForField("field"), instanceOf(latestLuceneCPClass));
         } else {