Remove much remaining frozen indices code (#120539)

This removes the transport action and the index setting.

The deprecation check has to go because the setting it uses to detect
frozen indices has gone. We are issueing a critical deprecation
warning in 8.last telling users to unfreeze them.

A lot of integration tests under `x-pack/plugin/sql` also have to go,
because they rely on being able to freeze indices.

ES-9736 #comment Removed the transport action and the index setting and so on in #120539

Author: PeteGillinElastic

x-pack/plugin/core/src/main/java/module-info.java

@@ -66,7 +66,6 @@
     exports org.elasticsearch.xpack.core.esql;
     exports org.elasticsearch.xpack.core.esql.action;
     exports org.elasticsearch.xpack.core.esql.action.internal; // TODO: qualify to esql when modularized
-    exports org.elasticsearch.xpack.core.frozen.action;
     exports org.elasticsearch.xpack.core.frozen;
     exports org.elasticsearch.xpack.core.graph.action;
     exports org.elasticsearch.xpack.core.graph;

x-pack/plugin/core/src/main/java/org/elasticsearch/index/engine/frozen/FrozenEngine.java

@@ -17,7 +17,6 @@
 import org.apache.lucene.store.Directory;
 import org.elasticsearch.common.lucene.Lucene;
 import org.elasticsearch.common.lucene.index.ElasticsearchDirectoryReader;
-import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.core.IOUtils;
 import org.elasticsearch.core.SuppressForbidden;
 import org.elasticsearch.index.engine.Engine;
@@ -55,12 +54,7 @@
  * stats in order to obtain the number of reopens.
  */
 public final class FrozenEngine extends ReadOnlyEngine {
-    public static final Setting<Boolean> INDEX_FROZEN = Setting.boolSetting(
-        "index.frozen",
-        false,
-        Setting.Property.IndexScope,
-        Setting.Property.PrivateIndex
-    );
+
     private final SegmentsStats segmentsStats;
     private final DocsStats docsStats;
     private volatile ElasticsearchDirectoryReader lastOpenedReader;

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/frozen/action/FreezeIndexAction.java

@@ -15,7 +15,6 @@
 import org.elasticsearch.index.IndexModule;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.IndexVersion;
-import org.elasticsearch.index.engine.frozen.FrozenEngine;
 import org.elasticsearch.xpack.core.deprecation.DeprecatedIndexPredicate;
 import org.elasticsearch.xpack.core.deprecation.DeprecationIssue;
 
@@ -71,7 +70,6 @@ private List<BiFunction<IndexMetadata, ClusterState, DeprecationIssue>> indexSet
             IndexDeprecationChecker::translogRetentionSettingCheck,
             IndexDeprecationChecker::checkIndexDataPath,
             IndexDeprecationChecker::storeTypeSettingCheck,
-            IndexDeprecationChecker::frozenIndexSettingCheck,
             IndexDeprecationChecker::deprecatedCamelCasePattern,
             IndexDeprecationChecker::legacyRoutingSettingCheck
         );
@@ -189,24 +187,6 @@ private static DeprecationIssue storeTypeSettingCheck(IndexMetadata indexMetadat
         return null;
     }
 
-    private static DeprecationIssue frozenIndexSettingCheck(IndexMetadata indexMetadata, ClusterState clusterState) {
-        Boolean isIndexFrozen = FrozenEngine.INDEX_FROZEN.get(indexMetadata.getSettings());
-        if (Boolean.TRUE.equals(isIndexFrozen)) {
-            String indexName = indexMetadata.getIndex().getName();
-            return new DeprecationIssue(
-                DeprecationIssue.Level.WARNING,
-                "index ["
-                    + indexName
-                    + "] is a frozen index. The frozen indices feature is deprecated and will be removed in a future version",
-                "https://www.elastic.co/guide/en/elasticsearch/reference/master/frozen-indices.html",
-                "Frozen indices no longer offer any advantages. Consider cold or frozen tiers in place of frozen indices.",
-                false,
-                null
-            );
-        }
-        return null;
-    }
-
     private static DeprecationIssue legacyRoutingSettingCheck(IndexMetadata indexMetadata, ClusterState clusterState) {
         List<String> deprecatedSettings = LegacyTiersDetection.getDeprecatedFilteredAllocationSettings(indexMetadata.getSettings());
         if (deprecatedSettings.isEmpty()) {

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/IndexDeprecationChecker.java

@@ -21,7 +21,6 @@
 import org.elasticsearch.index.IndexMode;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.IndexVersion;
-import org.elasticsearch.index.engine.frozen.FrozenEngine;
 import org.elasticsearch.indices.TestIndexNameExpressionResolver;
 import org.elasticsearch.snapshots.SearchableSnapshotsSettings;
 import org.elasticsearch.test.ESTestCase;
@@ -328,30 +327,6 @@ public void testSimpleFSSetting() {
         );
     }
 
-    public void testFrozenIndex() {
-        Settings.Builder settings = settings(IndexVersion.current());
-        settings.put(FrozenEngine.INDEX_FROZEN.getKey(), true);
-        IndexMetadata indexMetadata = IndexMetadata.builder("test").settings(settings).numberOfShards(1).numberOfReplicas(0).build();
-        ClusterState state = ClusterState.builder(ClusterState.EMPTY_STATE).metadata(Metadata.builder().put(indexMetadata, true)).build();
-        Map<String, List<DeprecationIssue>> issuesByIndex = checker.check(
-            state,
-            new DeprecationInfoAction.Request(TimeValue.THIRTY_SECONDS)
-        );
-        assertThat(
-            issuesByIndex.get("test"),
-            contains(
-                new DeprecationIssue(
-                    DeprecationIssue.Level.WARNING,
-                    "index [test] is a frozen index. The frozen indices feature is deprecated and will be removed in a future version",
-                    "https://www.elastic.co/guide/en/elasticsearch/reference/master/frozen-indices.html",
-                    "Frozen indices no longer offer any advantages. Consider cold or frozen tiers in place of frozen indices.",
-                    false,
-                    null
-                )
-            )
-        );
-    }
-
     public void testCamelCaseDeprecation() {
         String simpleMapping = "{\n\"_doc\": {"
             + "\"properties\" : {\n"

x-pack/plugin/deprecation/src/test/java/org/elasticsearch/xpack/deprecation/IndexDeprecationCheckerTests.java

@@ -8,30 +8,19 @@
 
 import org.elasticsearch.action.ActionRequest;
 import org.elasticsearch.action.ActionResponse;
-import org.elasticsearch.common.settings.Setting;
-import org.elasticsearch.index.engine.frozen.FrozenEngine;
 import org.elasticsearch.plugins.ActionPlugin;
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.xpack.core.action.XPackUsageFeatureAction;
-import org.elasticsearch.xpack.core.frozen.action.FreezeIndexAction;
-import org.elasticsearch.xpack.frozen.action.TransportFreezeIndexAction;
 
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.List;
 
 public class FrozenIndices extends Plugin implements ActionPlugin {
 
-    @Override
-    public List<Setting<?>> getSettings() {
-        return Arrays.asList(FrozenEngine.INDEX_FROZEN);
-    }
-
     @Override
     public List<ActionHandler<? extends ActionRequest, ? extends ActionResponse>> getActions() {
         List<ActionHandler<? extends ActionRequest, ? extends ActionResponse>> actions = new ArrayList<>();
         actions.add(new ActionHandler<>(XPackUsageFeatureAction.FROZEN_INDICES, FrozenIndicesUsageTransportAction.class));
-        actions.add(new ActionHandler<>(FreezeIndexAction.INSTANCE, TransportFreezeIndexAction.class));
         return actions;
     }
 }