SNAPSHOT - Shell of functionality, ready to slot in read only check

Author: lukewhiting

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

@@ -20,11 +20,16 @@ public class DeprecatedIndexPredicate {
 
     public static final IndexVersion MINIMUM_WRITEABLE_VERSION_AFTER_UPGRADE = IndexVersions.UPGRADE_TO_LUCENE_10_0_0;
 
-    /*
+    /**
      * This predicate allows through only indices that were created with a previous lucene version, meaning that they need to be reindexed
-     * in order to be writable in the _next_ lucene version.
+     * in order to be writable in the _next_ lucene version. It excludes searchable snapshots as they are not writable.
      *
      * It ignores searchable snapshots as they are not writable.
+     *
+     * @param metadata the cluster metadata
+     * @param filterToBlockedStatus if true, only indices that are write blocked will be returned,
+     *                              if false, only those without a block are returned
+     * @return a predicate that returns true for indices that need to be reindexed
      */
     public static Predicate<Index> getReindexRequiredPredicate(Metadata metadata, boolean filterToBlockedStatus) {
         return index -> {
@@ -33,6 +38,15 @@ public static Predicate<Index> getReindexRequiredPredicate(Metadata metadata, bo
         };
     }
 
+    /**
+     * This method check if the indices that were created with a previous lucene version, meaning that they need to be reindexed
+     * in order to be writable in the _next_ lucene version. It excludes searchable snapshots as they are not writable.
+     *
+     * @param indexMetadata the index metadata
+     * @param filterToBlockedStatus if true, only indices that are write blocked will be returned,
+     *                              if false, only those without a block are returned
+     * @return a predicate that returns true for indices that need to be reindexed
+     */
     public static boolean reindexRequired(IndexMetadata indexMetadata, boolean filterToBlockedStatus) {
         return creationVersionBeforeMinimumWritableVersion(indexMetadata)
             && isNotSearchableSnapshot(indexMetadata)

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

@@ -48,7 +48,7 @@ static DeprecationIssue oldIndicesCheck(DataStream dataStream, ClusterState clus
     static DeprecationIssue ignoredOldIndicesCheck(DataStream dataStream, ClusterState clusterState) {
         List<Index> backingIndices = dataStream.getIndices();
 
-        Set<String> ignoredIndices = getReIndexRequiredIndices(backingIndices, clusterState, false);
+        Set<String> ignoredIndices = getReIndexRequiredIndices(backingIndices, clusterState, true);
 
         if (ignoredIndices.isEmpty() == false) {
             return new DeprecationIssue(