Introduce a Few Settings Singleton Instances (#78897) (#78908)

This is mostly motivated by the ILM steps changes, that showed up as hot in
profiling since instantiating a `Settings` instance turns out to be somewhat expensive.
Also cleans up a couple of other spots and some duplication as well.

client/rest-high-level/src/main/java/org/elasticsearch/client/indices/CreateIndexRequest.java

@@ -36,8 +36,6 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
 
-import static org.elasticsearch.common.settings.Settings.Builder.EMPTY_SETTINGS;
-
 /**
  * A request to create an index.
  */
@@ -47,7 +45,7 @@ public class CreateIndexRequest extends TimedRequest implements Validatable, ToX
     static final ParseField ALIASES = new ParseField("aliases");
 
     private final String index;
-    private Settings settings = EMPTY_SETTINGS;
+    private Settings settings = Settings.EMPTY;
 
     private BytesReference mappings;
     private XContentType mappingsXContentType;

client/rest-high-level/src/main/java/org/elasticsearch/client/indices/IndexTemplateMetadata.java

@@ -178,7 +178,7 @@ public class IndexTemplateMetadata  {
 
         private List<String> indexPatterns;
 
-        private Settings settings = Settings.Builder.EMPTY_SETTINGS;
+        private Settings settings = Settings.EMPTY;
 
         private MappingMetadata mappings;
 

client/rest-high-level/src/main/java/org/elasticsearch/client/indices/PutIndexTemplateRequest.java

@@ -40,7 +40,6 @@ import java.util.Set;
 import java.util.stream.Collectors;
 
 import static org.elasticsearch.action.ValidateActions.addValidationError;
-import static org.elasticsearch.common.settings.Settings.Builder.EMPTY_SETTINGS;
 
 /**
  * A request to create an index template.
@@ -66,7 +65,7 @@ public class PutIndexTemplateRequest extends MasterNodeRequest<PutIndexTemplateR
 
     private boolean create;
 
-    private Settings settings = EMPTY_SETTINGS;
+    private Settings settings = Settings.EMPTY;
 
     private BytesReference mappings = null;
 

server/src/internalClusterTest/java/org/elasticsearch/recovery/SimpleRecoveryIT.java

@@ -29,7 +29,7 @@ public class SimpleRecoveryIT extends ESIntegTestCase {
     }
 
     protected Settings recoverySettings() {
-        return Settings.Builder.EMPTY_SETTINGS;
+        return Settings.EMPTY;
     }
 
     @Override

server/src/main/java/org/elasticsearch/action/admin/cluster/repositories/put/PutRepositoryRequest.java

@@ -21,7 +21,6 @@ import java.io.IOException;
 import java.util.Map;
 
 import static org.elasticsearch.action.ValidateActions.addValidationError;
-import static org.elasticsearch.common.settings.Settings.Builder.EMPTY_SETTINGS;
 import static org.elasticsearch.common.settings.Settings.readSettingsFromStream;
 import static org.elasticsearch.common.settings.Settings.writeSettingsToStream;
 
@@ -39,7 +38,7 @@ public class PutRepositoryRequest extends AcknowledgedRequest<PutRepositoryReque
 
     private boolean verify = true;
 
-    private Settings settings = EMPTY_SETTINGS;
+    private Settings settings = Settings.EMPTY;
 
     public PutRepositoryRequest(StreamInput in) throws IOException {
         super(in);

server/src/main/java/org/elasticsearch/action/admin/cluster/settings/ClusterUpdateSettingsRequest.java

@@ -26,7 +26,6 @@ import java.util.Map;
 import static org.elasticsearch.action.ValidateActions.addValidationError;
 import static org.elasticsearch.common.settings.Settings.readSettingsFromStream;
 import static org.elasticsearch.common.settings.Settings.writeSettingsToStream;
-import static org.elasticsearch.common.settings.Settings.Builder.EMPTY_SETTINGS;
 
 /**
  * Request for an update cluster settings action
@@ -44,8 +43,8 @@ public class ClusterUpdateSettingsRequest extends AcknowledgedRequest<ClusterUpd
         PARSER.declareObject((r, t) -> r.transientSettings = t, (p, c) -> Settings.fromXContent(p), TRANSIENT);
     }
 
-    private Settings transientSettings = EMPTY_SETTINGS;
+    private Settings transientSettings = Settings.EMPTY;
-    private Settings persistentSettings = EMPTY_SETTINGS;
+    private Settings persistentSettings = Settings.EMPTY;
 
     public ClusterUpdateSettingsRequest(StreamInput in) throws IOException {
         super(in);

server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/create/CreateSnapshotRequest.java

@@ -33,7 +33,6 @@ import java.util.Objects;
 
 import static org.elasticsearch.action.ValidateActions.addValidationError;
 import static org.elasticsearch.common.Strings.EMPTY_ARRAY;
-import static org.elasticsearch.common.settings.Settings.Builder.EMPTY_SETTINGS;
 import static org.elasticsearch.common.settings.Settings.readSettingsFromStream;
 import static org.elasticsearch.common.settings.Settings.writeSettingsToStream;
 import static org.elasticsearch.common.xcontent.support.XContentMapValues.nodeBooleanValue;
@@ -70,7 +69,7 @@ public class CreateSnapshotRequest extends MasterNodeRequest<CreateSnapshotReque
 
     private boolean partial = false;
 
-    private Settings settings = EMPTY_SETTINGS;
+    private Settings settings = Settings.EMPTY;
 
     private boolean includeGlobalState = true;
 

server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/restore/RestoreSnapshotRequest.java

@@ -31,7 +31,6 @@ import java.util.Map;
 import java.util.Objects;
 
 import static org.elasticsearch.action.ValidateActions.addValidationError;
-import static org.elasticsearch.common.settings.Settings.Builder.EMPTY_SETTINGS;
 import static org.elasticsearch.common.settings.Settings.readSettingsFromStream;
 import static org.elasticsearch.common.settings.Settings.writeSettingsToStream;
 import static org.elasticsearch.common.xcontent.support.XContentMapValues.nodeBooleanValue;
@@ -55,7 +54,7 @@ public class RestoreSnapshotRequest extends MasterNodeRequest<RestoreSnapshotReq
     private boolean includeGlobalState = false;
     private boolean partial = false;
     private boolean includeAliases = true;
-    private Settings indexSettings = EMPTY_SETTINGS;
+    private Settings indexSettings = Settings.EMPTY;
     private String[] ignoreIndexSettings = Strings.EMPTY_ARRAY;
 
     // This field does not get serialised (except toString for debugging purpose) because it is always set locally by authz

server/src/main/java/org/elasticsearch/action/admin/indices/create/CreateIndexClusterStateUpdateRequest.java

@@ -38,7 +38,7 @@ public class CreateIndexClusterStateUpdateRequest extends ClusterStateUpdateRequ
     private boolean copySettings;
     private SystemDataStreamDescriptor systemDataStreamDescriptor;
 
-    private Settings settings = Settings.Builder.EMPTY_SETTINGS;
+    private Settings settings = Settings.EMPTY;
 
     private final Map<String, String> mappings = new HashMap<>();
 

server/src/main/java/org/elasticsearch/action/admin/indices/create/CreateIndexRequest.java

@@ -45,7 +45,6 @@ import java.util.Objects;
 import java.util.Set;
 
 import static org.elasticsearch.action.ValidateActions.addValidationError;
-import static org.elasticsearch.common.settings.Settings.Builder.EMPTY_SETTINGS;
 import static org.elasticsearch.common.settings.Settings.readSettingsFromStream;
 import static org.elasticsearch.common.settings.Settings.writeSettingsToStream;
 
@@ -68,7 +67,7 @@ public class CreateIndexRequest extends AcknowledgedRequest<CreateIndexRequest>
 
     private String index;
 
-    private Settings settings = EMPTY_SETTINGS;
+    private Settings settings = Settings.EMPTY;
 
     private final Map<String, String> mappings = new HashMap<>();
 
@@ -127,7 +126,7 @@ public class CreateIndexRequest extends AcknowledgedRequest<CreateIndexRequest>
      * @param index the name of the index
      */
     public CreateIndexRequest(String index) {
-        this(index, EMPTY_SETTINGS);
+        this(index, Settings.EMPTY);
     }
 
     /**

server/src/main/java/org/elasticsearch/action/admin/indices/rollover/MetadataRolloverService.java

@@ -55,6 +55,8 @@ public class MetadataRolloverService {
     private static final Pattern INDEX_NAME_PATTERN = Pattern.compile("^.*-\\d+$");
     private static final List<IndexAbstraction.Type> VALID_ROLLOVER_TARGETS = org.elasticsearch.core.List.of(ALIAS, DATA_STREAM);
 
+    public static final Settings HIDDEN_INDEX_SETTINGS = Settings.builder().put(IndexMetadata.SETTING_INDEX_HIDDEN, true).build();
+
     private final ThreadPool threadPool;
     private final MetadataCreateIndexService createIndexService;
     private final MetadataIndexAliasesService indexAliasesService;
@@ -276,7 +278,7 @@ public class MetadataRolloverService {
                                                                                     final String targetIndexName,
                                                                                     CreateIndexRequest createIndexRequest,
                                                                                     final SystemDataStreamDescriptor descriptor) {
-        Settings settings = descriptor != null ? Settings.EMPTY : Settings.builder().put("index.hidden", true).build();
+        Settings settings = descriptor != null ? Settings.EMPTY : HIDDEN_INDEX_SETTINGS;
         return prepareCreateIndexRequest(targetIndexName, targetIndexName, "rollover_data_stream", createIndexRequest, settings)
             .dataStreamName(dataStreamName)
             .systemDataStreamDescriptor(descriptor);

server/src/main/java/org/elasticsearch/action/admin/indices/settings/put/UpdateSettingsRequest.java

@@ -31,7 +31,6 @@ import java.util.Objects;
 import static org.elasticsearch.action.ValidateActions.addValidationError;
 import static org.elasticsearch.common.settings.Settings.readSettingsFromStream;
 import static org.elasticsearch.common.settings.Settings.writeSettingsToStream;
-import static org.elasticsearch.common.settings.Settings.Builder.EMPTY_SETTINGS;
 
 /**
  * Request for an update index settings action
@@ -43,7 +42,7 @@ public class UpdateSettingsRequest extends AcknowledgedRequest<UpdateSettingsReq
 
     private String[] indices;
     private IndicesOptions indicesOptions = DEFAULT_INDICES_OPTIONS;
-    private Settings settings = EMPTY_SETTINGS;
+    private Settings settings = Settings.EMPTY;
     private boolean preserveExisting = false;
     private String origin = "";
 

server/src/main/java/org/elasticsearch/action/admin/indices/template/put/PutIndexTemplateRequest.java

@@ -48,7 +48,6 @@ import java.util.Set;
 import java.util.stream.Collectors;
 
 import static org.elasticsearch.action.ValidateActions.addValidationError;
-import static org.elasticsearch.common.settings.Settings.Builder.EMPTY_SETTINGS;
 import static org.elasticsearch.common.settings.Settings.readSettingsFromStream;
 import static org.elasticsearch.common.settings.Settings.writeSettingsToStream;
 
@@ -69,7 +68,7 @@ public class PutIndexTemplateRequest extends MasterNodeRequest<PutIndexTemplateR
 
     private boolean create;
 
-    private Settings settings = EMPTY_SETTINGS;
+    private Settings settings = Settings.EMPTY;
 
     private Map<String, String> mappings = new HashMap<>();
 

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

@@ -1069,7 +1069,7 @@ public class IndexMetadata implements Diffable<IndexMetadata>, ToXContentFragmen
         private long settingsVersion = 1;
         private long aliasesVersion = 1;
         private long[] primaryTerms = null;
-        private Settings settings = Settings.Builder.EMPTY_SETTINGS;
+        private Settings settings = Settings.EMPTY;
         private final ImmutableOpenMap.Builder<String, MappingMetadata> mappings;
         private final ImmutableOpenMap.Builder<String, AliasMetadata> aliases;
         private final ImmutableOpenMap.Builder<String, DiffableStringMap> customMetadata;

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

@@ -254,7 +254,7 @@ public class IndexTemplateMetadata extends AbstractDiffable<IndexTemplateMetadat
 
         private List<String> indexPatterns;
 
-        private Settings settings = Settings.Builder.EMPTY_SETTINGS;
+        private Settings settings = Settings.EMPTY;
 
         private final ImmutableOpenMap.Builder<String, CompressedXContent> mappings;
 

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

@@ -1151,8 +1151,8 @@ public class Metadata implements Iterable<IndexMetadata>, Diffable<Metadata>, To
         private long version;
 
         private CoordinationMetadata coordinationMetadata = CoordinationMetadata.EMPTY_METADATA;
-        private Settings transientSettings = Settings.Builder.EMPTY_SETTINGS;
+        private Settings transientSettings = Settings.EMPTY;
-        private Settings persistentSettings = Settings.Builder.EMPTY_SETTINGS;
+        private Settings persistentSettings = Settings.EMPTY;
         private DiffableStringMap hashesOfConsistentSettings = DiffableStringMap.EMPTY;
 
         private final ImmutableOpenMap.Builder<String, IndexMetadata> indices;

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

@@ -14,6 +14,7 @@ import org.elasticsearch.ResourceAlreadyExistsException;
 import org.elasticsearch.Version;
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.action.admin.indices.create.CreateIndexClusterStateUpdateRequest;
+import org.elasticsearch.action.admin.indices.rollover.MetadataRolloverService;
 import org.elasticsearch.action.support.ActiveShardCount;
 import org.elasticsearch.action.support.ActiveShardsObserver;
 import org.elasticsearch.action.support.master.AcknowledgedResponse;
@@ -23,7 +24,6 @@ import org.elasticsearch.cluster.ack.ClusterStateUpdateRequest;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.Priority;
 import org.elasticsearch.common.Strings;
-import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.index.Index;
 import org.elasticsearch.index.mapper.DataStreamTimestampFieldMapper;
@@ -202,7 +202,7 @@ public class MetadataCreateDataStreamService {
                     .systemDataStreamDescriptor(systemDataStreamDescriptor);
 
             if (isSystem == false) {
-                createIndexRequest.settings(Settings.builder().put("index.hidden", true).build());
+                createIndexRequest.settings(MetadataRolloverService.HIDDEN_INDEX_SETTINGS);
             }
 
             try {

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

@@ -1417,7 +1417,7 @@ public class MetadataIndexTemplateService {
         int order;
         Integer version;
         List<String> indexPatterns;
-        Settings settings = Settings.Builder.EMPTY_SETTINGS;
+        Settings settings = Settings.EMPTY;
         Map<String, String> mappings = new HashMap<>();
         List<Alias> aliases = new ArrayList<>();
 

server/src/main/java/org/elasticsearch/cluster/routing/allocation/DataTier.java

@@ -21,12 +21,12 @@ import org.elasticsearch.index.shard.IndexSettingProvider;
 import org.elasticsearch.snapshots.SearchableSnapshotsSettings;
 
 import java.util.Collection;
+import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.function.Function;
-import java.util.stream.Collectors;
 
 /**
  * The {@code DataTier} class encapsulates the formalization of the "content",
@@ -49,6 +49,12 @@ public class DataTier {
 
     public static final Setting.Validator<String> DATA_TIER_SETTING_VALIDATOR = new DataTierSettingValidator();
 
+    private static final Settings DATA_CONTENT_TIER_PREFERENCE_SETTINGS = Settings.builder().put(TIER_PREFERENCE, DATA_CONTENT).build();
+
+    private static final Settings DATA_HOT_TIER_PREFERENCE_SETTINGS = Settings.builder().put(TIER_PREFERENCE, DATA_HOT).build();
+
+    private static final Settings NULL_TIER_PREFERENCE_SETTINGS = Settings.builder().putNull(TIER_PREFERENCE).build();
+
     public static final Setting<String> TIER_PREFERENCE_SETTING = new Setting<>(
         new Setting.SimpleKey(TIER_PREFERENCE),
         DataTierSettingValidator::getDefaultTierPreference,
@@ -70,6 +76,24 @@ public class DataTier {
     private static final List<String> ORDERED_FROZEN_TO_HOT_TIERS =
         org.elasticsearch.core.List.of(DATA_FROZEN, DATA_COLD, DATA_WARM, DATA_HOT);
 
+    private static final Map<String, String> PREFERENCE_TIER_CONFIGURATIONS;
+
+    private static final Map<String, Settings> PREFERENCE_TIER_CONFIGURATION_SETTINGS;
+
+    static {
+        final Map<String, String> tmp = new HashMap<>();
+        final Map<String, Settings> tmpSettings = new HashMap<>();
+        for (int i = 0, ordered_frozen_to_hot_tiersSize = ORDERED_FROZEN_TO_HOT_TIERS.size(); i < ordered_frozen_to_hot_tiersSize; i++) {
+            String tier = ORDERED_FROZEN_TO_HOT_TIERS.get(i);
+            final String prefTierString =
+                String.join(",", ORDERED_FROZEN_TO_HOT_TIERS.subList(i, ORDERED_FROZEN_TO_HOT_TIERS.size())).intern();
+            tmp.put(tier, prefTierString);
+            tmpSettings.put(tier, Settings.builder().put(DataTier.TIER_PREFERENCE, prefTierString).build());
+        }
+        PREFERENCE_TIER_CONFIGURATIONS = org.elasticsearch.core.Map.copyOf(tmp);
+        PREFERENCE_TIER_CONFIGURATION_SETTINGS = org.elasticsearch.core.Map.copyOf(tmpSettings);
+    }
+
     /**
      * Returns true if the given tier name is a valid tier
      */
@@ -83,11 +107,19 @@ public class DataTier {
      * This is usually used in conjunction with {@link #TIER_PREFERENCE_SETTING}.
      */
     public static String getPreferredTiersConfiguration(String targetTier) {
-        int indexOfTargetTier = ORDERED_FROZEN_TO_HOT_TIERS.indexOf(targetTier);
+        final String res = PREFERENCE_TIER_CONFIGURATIONS.get(targetTier);
-        if (indexOfTargetTier == -1) {
+        if (res == null) {
             throw new IllegalArgumentException("invalid data tier [" + targetTier + "]");
         }
-        return ORDERED_FROZEN_TO_HOT_TIERS.stream().skip(indexOfTargetTier).collect(Collectors.joining(","));
+        return res;
+    }
+
+    public static Settings getPreferredTiersConfigurationSettings(String targetTier) {
+        final Settings res = PREFERENCE_TIER_CONFIGURATION_SETTINGS.get(targetTier);
+        if (res == null) {
+            throw new IllegalArgumentException("invalid data tier [" + targetTier + "]");
+        }
+        return res;
     }
 
     /**
@@ -157,7 +189,7 @@ public class DataTier {
             Set<String> settings = indexSettings.keySet();
             if (settings.contains(TIER_PREFERENCE)) {
                 // just a marker -- this null value will be removed or overridden by the template/request settings
-                return Settings.builder().putNull(TIER_PREFERENCE).build();
+                return NULL_TIER_PREFERENCE_SETTINGS;
             } else if (settings.stream().anyMatch(s -> s.startsWith(IndexMetadata.INDEX_ROUTING_REQUIRE_GROUP_PREFIX + ".")) ||
                 settings.stream().anyMatch(s -> s.startsWith(IndexMetadata.INDEX_ROUTING_EXCLUDE_GROUP_PREFIX + ".")) ||
                 settings.stream().anyMatch(s -> s.startsWith(IndexMetadata.INDEX_ROUTING_INCLUDE_GROUP_PREFIX + "."))) {
@@ -169,9 +201,9 @@ public class DataTier {
                 // tier if the index is part of a data stream, the "content"
                 // tier if it is not.
                 if (isDataStreamIndex) {
-                    return Settings.builder().put(TIER_PREFERENCE, DATA_HOT).build();
+                    return DATA_HOT_TIER_PREFERENCE_SETTINGS;
                 } else {
-                    return Settings.builder().put(TIER_PREFERENCE, DATA_CONTENT).build();
+                    return DATA_CONTENT_TIER_PREFERENCE_SETTINGS;
                 }
             }
         }

server/src/main/java/org/elasticsearch/cluster/routing/allocation/DiskThresholdMonitor.java

@@ -59,6 +59,12 @@ public class DiskThresholdMonitor {
 
     private static final Logger logger = LogManager.getLogger(DiskThresholdMonitor.class);
 
+    private static final Settings READ_ONLY_ALLOW_DELETE_SETTINGS = Settings.builder()
+        .put(IndexMetadata.SETTING_READ_ONLY_ALLOW_DELETE, Boolean.TRUE.toString()).build();
+
+    private static final Settings NOT_READ_ONLY_ALLOW_DELETE_SETTINGS =
+        Settings.builder().putNull(IndexMetadata.SETTING_READ_ONLY_ALLOW_DELETE).build();
+
     private final DiskThresholdSettings diskThresholdSettings;
     private final Client client;
     private final Supplier<ClusterState> clusterStateSupplier;
@@ -378,9 +384,7 @@ public class DiskThresholdMonitor {
             setLastRunTimeMillis();
             listener.onFailure(e);
         });
-        Settings readOnlySettings = readOnly ? Settings.builder()
+        Settings readOnlySettings = readOnly ? READ_ONLY_ALLOW_DELETE_SETTINGS : NOT_READ_ONLY_ALLOW_DELETE_SETTINGS;
-            .put(IndexMetadata.SETTING_READ_ONLY_ALLOW_DELETE, Boolean.TRUE.toString()).build() :
-            Settings.builder().putNull(IndexMetadata.SETTING_READ_ONLY_ALLOW_DELETE).build();
         client.admin().indices().prepareUpdateSettings(indicesToUpdate.toArray(Strings.EMPTY_ARRAY))
             .setSettings(readOnlySettings)
             .execute(wrappedListener.map(r -> null));

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

@@ -762,8 +762,6 @@ public final class Settings implements ToXContentFragment {
      */
     public static class Builder {
 
-        public static final Settings EMPTY_SETTINGS = new Builder().build();
-
         // we use a sorted map for consistent serialization when using getAsMap()
         private final Map<String, Object> map = new TreeMap<>();
 

server/src/main/java/org/elasticsearch/index/analysis/AnalysisRegistry.java

@@ -538,7 +538,7 @@ public final class AnalysisRegistry implements Closeable {
         if (analyzers.containsKey(DEFAULT_ANALYZER_NAME) == false) {
             analyzers.put(DEFAULT_ANALYZER_NAME,
                     produceAnalyzer(DEFAULT_ANALYZER_NAME,
-                            new StandardAnalyzerProvider(indexSettings, null, DEFAULT_ANALYZER_NAME, Settings.Builder.EMPTY_SETTINGS),
+                            new StandardAnalyzerProvider(indexSettings, null, DEFAULT_ANALYZER_NAME, Settings.EMPTY),
                             tokenFilterFactoryFactories, charFilterFactoryFactories, tokenizerFactoryFactories));
         }
         NamedAnalyzer defaultAnalyzer = analyzers.get(DEFAULT_ANALYZER_NAME);

server/src/main/java/org/elasticsearch/plugins/Plugin.java

@@ -125,7 +125,7 @@ public abstract class Plugin implements Closeable {
      * overwritten with the additional settings. These settings added if they don't exist.
      */
     public Settings additionalSettings() {
-        return Settings.Builder.EMPTY_SETTINGS;
+        return Settings.EMPTY;
     }
 
     /**

server/src/test/java/org/elasticsearch/cluster/routing/allocation/BalanceConfigurationTests.java

@@ -264,7 +264,7 @@ public class BalanceConfigurationTests extends ESAllocationTestCase {
     public void testNoRebalanceOnPrimaryOverload() {
         Settings.Builder settings = Settings.builder();
         AllocationService strategy = new AllocationService(randomAllocationDeciders(settings.build(),
-                new ClusterSettings(Settings.Builder.EMPTY_SETTINGS, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS), random()),
+                new ClusterSettings(Settings.EMPTY, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS), random()),
                 new TestGatewayAllocator(), new ShardsAllocator() {
             /*
              *  // this allocator tries to rebuild this scenario where a rebalance is

server/src/test/java/org/elasticsearch/index/IndexSortSettingsTests.java

@@ -28,7 +28,6 @@ import org.elasticsearch.test.ESTestCase;
 import java.util.Collections;
 import java.util.function.Supplier;
 
-import static org.elasticsearch.common.settings.Settings.Builder.EMPTY_SETTINGS;
 import static org.elasticsearch.index.IndexSettingsTests.newIndexMeta;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
@@ -40,7 +39,7 @@ public class IndexSortSettingsTests extends ESTestCase {
     }
 
     public void testNoIndexSort() {
-        IndexSettings indexSettings = indexSettings(EMPTY_SETTINGS);
+        IndexSettings indexSettings = indexSettings(Settings.EMPTY);
         assertFalse(indexSettings.getIndexSortConfig().hasIndexSort());
     }
 

server/src/test/java/org/elasticsearch/index/MergePolicySettingsTests.java

@@ -16,7 +16,6 @@ import org.elasticsearch.test.ESTestCase;
 
 import java.io.IOException;
 
-import static org.elasticsearch.common.settings.Settings.Builder.EMPTY_SETTINGS;
 import static org.elasticsearch.index.IndexSettingsTests.newIndexMeta;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
@@ -54,7 +53,7 @@ public class MergePolicySettingsTests extends ESTestCase {
     }
 
     public void testUpdateSettings() throws IOException {
-        IndexSettings indexSettings = indexSettings(EMPTY_SETTINGS);
+        IndexSettings indexSettings = indexSettings(Settings.EMPTY);
         assertThat(indexSettings.getMergePolicy().getNoCFSRatio(), equalTo(0.1));
         indexSettings = indexSettings(build(0.9));
         assertThat((indexSettings.getMergePolicy()).getNoCFSRatio(), equalTo(0.9));
@@ -131,7 +130,7 @@ public class MergePolicySettingsTests extends ESTestCase {
                 Settings.builder().put(MergePolicyConfig.INDEX_MERGE_POLICY_DELETES_PCT_ALLOWED_SETTING.getKey(), 53).build())));
         final Throwable cause = exc.getCause();
         assertThat(cause.getMessage(), containsString("must be <= 50.0"));
-        indexSettings.updateIndexMetadata(newIndexMeta("index", EMPTY_SETTINGS)); // see if defaults are restored
+        indexSettings.updateIndexMetadata(newIndexMeta("index", Settings.EMPTY)); // see if defaults are restored
         assertEquals(((EsTieredMergePolicy) indexSettings.getMergePolicy()).getForceMergeDeletesPctAllowed(),
             MergePolicyConfig.DEFAULT_EXPUNGE_DELETES_ALLOWED, 0.0d);
         assertEquals(((EsTieredMergePolicy) indexSettings.getMergePolicy()).getFloorSegmentMB(),

test/framework/src/main/java/org/elasticsearch/cluster/ESAllocationTestCase.java

@@ -60,7 +60,7 @@ public abstract class ESAllocationTestCase extends ESTestCase {
     };
 
     public static MockAllocationService createAllocationService() {
-        return createAllocationService(Settings.Builder.EMPTY_SETTINGS);
+        return createAllocationService(Settings.EMPTY);
     }
 
     public static MockAllocationService createAllocationService(Settings settings) {

test/framework/src/main/java/org/elasticsearch/index/analysis/MyFilterTokenFilterFactory.java

@@ -17,7 +17,7 @@ import org.elasticsearch.index.IndexSettings;
 public class MyFilterTokenFilterFactory extends AbstractTokenFilterFactory {
 
     public MyFilterTokenFilterFactory(IndexSettings indexSettings, Environment env, String name, Settings settings) {
-        super(indexSettings, name, Settings.Builder.EMPTY_SETTINGS);
+        super(indexSettings, name, Settings.EMPTY);
     }
 
     @Override

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/ForceMergeAction.java

@@ -36,6 +36,11 @@ import java.util.Objects;
 public class ForceMergeAction implements LifecycleAction {
     private static final Logger logger = LogManager.getLogger(ForceMergeAction.class);
 
+    private static final Settings READ_ONLY_SETTINGS = Settings.builder().put(IndexMetadata.SETTING_BLOCKS_WRITE, true).build();
+
+    private static final Settings BEST_COMPRESSION_SETTINGS =
+        Settings.builder().put(EngineConfig.INDEX_CODEC_SETTING.getKey(), CodecService.BEST_COMPRESSION_CODEC).build();
+
     public static final String NAME = "forcemerge";
     public static final ParseField MAX_NUM_SEGMENTS_FIELD = new ParseField("max_num_segments");
     public static final ParseField CODEC = new ParseField("index_codec");
@@ -120,10 +125,6 @@ public class ForceMergeAction implements LifecycleAction {
 
     @Override
     public List<Step> toSteps(Client client, String phase, Step.StepKey nextStepKey) {
-        Settings readOnlySettings = Settings.builder().put(IndexMetadata.SETTING_BLOCKS_WRITE, true).build();
-        Settings bestCompressionSettings = Settings.builder()
-            .put(EngineConfig.INDEX_CODEC_SETTING.getKey(), CodecService.BEST_COMPRESSION_CODEC).build();
-
         final boolean codecChange = codec != null && codec.equals(CodecService.BEST_COMPRESSION_CODEC);
 
         StepKey preForceMergeBranchingKey = new StepKey(phase, NAME, CONDITIONAL_SKIP_FORCE_MERGE_STEP);
@@ -153,11 +154,11 @@ public class ForceMergeAction implements LifecycleAction {
         CheckNotDataStreamWriteIndexStep checkNotWriteIndexStep = new CheckNotDataStreamWriteIndexStep(checkNotWriteIndex,
             readOnlyKey);
         UpdateSettingsStep readOnlyStep =
-            new UpdateSettingsStep(readOnlyKey, codecChange ? closeKey : forceMergeKey, client, readOnlySettings);
+            new UpdateSettingsStep(readOnlyKey, codecChange ? closeKey : forceMergeKey, client, READ_ONLY_SETTINGS);
 
         CloseIndexStep closeIndexStep = new CloseIndexStep(closeKey, updateCompressionKey, client);
         UpdateSettingsStep updateBestCompressionSettings = new UpdateSettingsStep(updateCompressionKey,
-            openKey, client, bestCompressionSettings);
+            openKey, client, BEST_COMPRESSION_SETTINGS);
         OpenIndexStep openIndexStep = new OpenIndexStep(openKey, waitForGreenIndexKey, client);
         WaitForIndexColorStep waitForIndexGreenStep = new WaitForIndexColorStep(waitForGreenIndexKey,
             forceMergeKey, ClusterHealthStatus.GREEN);

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/MigrateAction.java

@@ -25,7 +25,7 @@ import java.io.IOException;
 import java.util.List;
 import java.util.Objects;
 
-import static org.elasticsearch.cluster.routing.allocation.DataTier.getPreferredTiersConfiguration;
+import static org.elasticsearch.cluster.routing.allocation.DataTier.getPreferredTiersConfigurationSettings;
 
 /**
  * A {@link LifecycleAction} which enables or disables the automatic migration of data between
@@ -115,9 +115,7 @@ public class MigrateAction implements LifecycleAction {
                     return false;
                 });
             UpdateSettingsStep updateMigrationSettingStep = new UpdateSettingsStep(migrationKey, migrationRoutedKey, client,
-                Settings.builder()
+                getPreferredTiersConfigurationSettings(targetTier));
-                    .put(DataTier.TIER_PREFERENCE, getPreferredTiersConfiguration(targetTier))
-                    .build());
             DataTierMigrationRoutedStep migrationRoutedStep = new DataTierMigrationRoutedStep(migrationRoutedKey, nextStepKey);
             return org.elasticsearch.core.List.of(conditionalSkipActionStep, updateMigrationSettingStep, migrationRoutedStep);
         } else {

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/RolloverAction.java

@@ -42,6 +42,8 @@ public class RolloverAction implements LifecycleAction {
     public static final Setting<String> LIFECYCLE_ROLLOVER_ALIAS_SETTING = Setting.simpleString(LIFECYCLE_ROLLOVER_ALIAS,
         Setting.Property.Dynamic, Setting.Property.IndexScope);
 
+    private static final Settings INDEXING_COMPLETE = Settings.builder().put(LifecycleSettings.LIFECYCLE_INDEXING_COMPLETE, true).build();
+
     private static final ConstructingObjectParser<RolloverAction, Void> PARSER = new ConstructingObjectParser<>(NAME,
         a -> new RolloverAction((ByteSizeValue) a[0], (ByteSizeValue) a[1], (TimeValue) a[2], (Long) a[3]));
 
@@ -168,8 +170,6 @@ public class RolloverAction implements LifecycleAction {
 
     @Override
     public List<Step> toSteps(Client client, String phase, Step.StepKey nextStepKey) {
-        Settings indexingComplete = Settings.builder().put(LifecycleSettings.LIFECYCLE_INDEXING_COMPLETE, true).build();
-
         StepKey waitForRolloverReadyStepKey = new StepKey(phase, NAME, WaitForRolloverReadyStep.NAME);
         StepKey rolloverStepKey = new StepKey(phase, NAME, RolloverStep.NAME);
         StepKey waitForActiveShardsKey = new StepKey(phase, NAME, WaitForActiveShardsStep.NAME);
@@ -183,7 +183,7 @@ public class RolloverAction implements LifecycleAction {
         UpdateRolloverLifecycleDateStep updateDateStep = new UpdateRolloverLifecycleDateStep(updateDateStepKey, setIndexingCompleteStepKey,
             System::currentTimeMillis);
         UpdateSettingsStep setIndexingCompleteStep = new UpdateSettingsStep(setIndexingCompleteStepKey, nextStepKey,
-            client, indexingComplete);
+            client, INDEXING_COMPLETE);
         return Arrays.asList(waitForRolloverReadyStep, rolloverStep, waitForActiveShardsStep, updateDateStep, setIndexingCompleteStep);
     }
 

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/SetPriorityAction.java

@@ -35,6 +35,9 @@ public class SetPriorityAction implements LifecycleAction {
     private static final ConstructingObjectParser<SetPriorityAction, Void> PARSER = new ConstructingObjectParser<>(NAME,
         a -> new SetPriorityAction((Integer) a[0]));
 
+    private static final Settings NULL_PRIORITY_SETTINGS =
+        Settings.builder().putNull(IndexMetadata.INDEX_PRIORITY_SETTING.getKey()).build();
+
     //package private for testing
     final Integer recoveryPriority;
 
@@ -90,7 +93,7 @@ public class SetPriorityAction implements LifecycleAction {
     public List<Step> toSteps(Client client, String phase, StepKey nextStepKey) {
         StepKey key = new StepKey(phase, NAME, NAME);
         Settings indexPriority = recoveryPriority == null ?
-            Settings.builder().putNull(IndexMetadata.INDEX_PRIORITY_SETTING.getKey()).build()
+                NULL_PRIORITY_SETTINGS
             : Settings.builder().put(IndexMetadata.INDEX_PRIORITY_SETTING.getKey(), recoveryPriority).build();
         return Collections.singletonList(new UpdateSettingsStep(key, nextStepKey, client, indexPriority));
     }

x-pack/plugin/rollup/src/main/java/org/elasticsearch/xpack/rollup/v2/TransportRollupAction.java

@@ -13,6 +13,7 @@ import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.action.admin.indices.create.CreateIndexClusterStateUpdateRequest;
 import org.elasticsearch.action.admin.indices.create.CreateIndexRequest;
 import org.elasticsearch.action.admin.indices.delete.DeleteIndexRequest;
+import org.elasticsearch.action.admin.indices.rollover.MetadataRolloverService;
 import org.elasticsearch.action.admin.indices.settings.put.UpdateSettingsRequest;
 import org.elasticsearch.action.admin.indices.shrink.ResizeRequest;
 import org.elasticsearch.action.admin.indices.shrink.ResizeType;
@@ -71,6 +72,9 @@ public class TransportRollupAction extends AcknowledgedTransportMasterNodeAction
 
     private static final Logger logger = LogManager.getLogger(TransportRollupAction.class);
 
+    private static final Settings VISIBLE_INDEX_SETTINGS = Settings.builder().put(IndexMetadata.SETTING_INDEX_HIDDEN, false).build();
+    private static final Settings WRITE_BLOCKED_SETTINGS = Settings.builder().put(IndexMetadata.SETTING_BLOCKS_WRITE, true).build();
+
     private final Client client;
     private final ClusterService clusterService;
     private final MetadataCreateIndexService metadataCreateIndexService;
@@ -152,16 +156,13 @@ public class TransportRollupAction extends AcknowledgedTransportMasterNodeAction
             "rollup",
             tmpIndexName,
             tmpIndexName
-        ).settings(Settings.builder().put(IndexMetadata.SETTING_INDEX_HIDDEN, true).build()).mappings(mappingAsMap);
+        ).settings(MetadataRolloverService.HIDDEN_INDEX_SETTINGS).mappings(mappingAsMap);
 
         RollupIndexerAction.Request rollupIndexerRequest = new RollupIndexerAction.Request(request);
         ResizeRequest resizeRequest = new ResizeRequest(request.getRollupIndex(), tmpIndexName);
         resizeRequest.setResizeType(ResizeType.CLONE);
-        resizeRequest.getTargetIndexRequest().settings(Settings.builder().put(IndexMetadata.SETTING_INDEX_HIDDEN, false).build());
+        resizeRequest.getTargetIndexRequest().settings(VISIBLE_INDEX_SETTINGS);
-        UpdateSettingsRequest updateSettingsReq = new UpdateSettingsRequest(
+        UpdateSettingsRequest updateSettingsReq = new UpdateSettingsRequest(WRITE_BLOCKED_SETTINGS, tmpIndexName);
-            Settings.builder().put(IndexMetadata.SETTING_BLOCKS_WRITE, true).build(),
-            tmpIndexName
-        );
 
         // 1. validate Rollup Config against Field Caps
         // 2. create hidden temporary index