Adds REINDEX_PIT_SEARCH_ENABLED Feature Flag

modules/reindex-management/src/main/java/org/elasticsearch/reindex/management/ReindexManagementFeatures.java

@@ -13,6 +13,7 @@
 import org.elasticsearch.features.NodeFeature;
 import org.elasticsearch.reindex.ReindexPlugin;
 
+import java.util.HashSet;
 import java.util.Set;
 
 public class ReindexManagementFeatures implements FeatureSpecification {
@@ -21,9 +22,17 @@ public class ReindexManagementFeatures implements FeatureSpecification {
 
     @Override
     public Set<NodeFeature> getFeatures() {
-        // TODO: Before we release this functionality by removing the REINDEX_RESILIENCE_ENABLED checks, we should see whether we can
+        final Set<NodeFeature> features = new HashSet<>();
+        // TODO: Before we release any functionality behind FeatureFlags, we should see whether we can
         // consolidate the node features. These are a constrained resource, so we should combine the features for anything that is being
         // released at the same time while we still can.
-        return ReindexPlugin.REINDEX_RESILIENCE_ENABLED ? Set.of(NEW_ENDPOINTS, ReindexPlugin.RELOCATE_ON_SHUTDOWN_NODE_FEATURE) : Set.of();
+        if (ReindexPlugin.REINDEX_RESILIENCE_ENABLED) {
+            features.add(NEW_ENDPOINTS);
+            features.add(ReindexPlugin.RELOCATE_ON_SHUTDOWN_NODE_FEATURE);
+        }
+        if (ReindexPlugin.REINDEX_PIT_SEARCH_ENABLED) {
+            features.add(ReindexPlugin.REINDEX_PIT_SEARCH_FEATURE);
+        }
+        return Set.copyOf(features);
     }
 }

modules/reindex/src/main/java/org/elasticsearch/reindex/ReindexPlugin.java

@@ -49,17 +49,23 @@ public class ReindexPlugin extends Plugin implements ActionPlugin, ExtensiblePlu
 
     public static final ActionType<ListTasksResponse> RETHROTTLE_ACTION = new ActionType<>("cluster:admin/reindex/rethrottle");
 
-    // N.B. We declare this in the reindex module, so that we can check whether the feature is available on the cluster here - but we
-    // register it via a FeatureSpecification in the reindex-management module, to work around build problems caused by doing it here.
+    // N.B. We declare these in the reindex module, so that we can check whether the features are available on the cluster here - but we
+    // register them via a FeatureSpecification in the reindex-management module, to work around build problems caused by doing it here.
     // (The enrich plugin depends on this module, and registering features leads to either duplicate feature or JAR hell errors.)
     // (This approach means that the functionality requires both reindex and reindex-management modules to be present and enabled.)
     public static final NodeFeature RELOCATE_ON_SHUTDOWN_NODE_FEATURE = new NodeFeature("reindex_relocate_on_shutdown");
+    public static final NodeFeature REINDEX_PIT_SEARCH_FEATURE = new NodeFeature("reindex_pit_search");
 
     /**
      * Whether the feature flag to guard the work to make reindex more resilient while it is under development.
      */
     public static final boolean REINDEX_RESILIENCE_ENABLED = new FeatureFlag("reindex_resilience").isEnabled();
 
+    /**
+     * Guards the development work to change reindexing to use point in time (PIT) searching
+     */
+    public static final boolean REINDEX_PIT_SEARCH_ENABLED = new FeatureFlag("reindex_pit_search").isEnabled();
+
     @Override
     public List<ActionHandler> getActions() {
         return Arrays.asList(