Make NodeEnvironment.indexPaths singular

[rjernst]

This commit renames the indexPaths method to be singular and return a
single Path instead of an array. This is done in isolation from other
NodeEnvironment methods to make it reviewable.

relates #71205

[elasticmachine]

Pinging @elastic/es-core-infra (Team:Core/Infra)

[DaveCTurner]

LGTM, one optional suggestion which could be done in a followup instead.

[DaveCTurner]

It'd be nice to make this listener a Consumer<Path> too to get rid of this subscript (or else assert listener.get().length == 1 maybe?). It's actually only used in this one place, all other consumers just ignore it:

diff --git a/server/src/internalClusterTest/java/org/elasticsearch/plugins/IndexFoldersDeletionListenerIT.java b/server/src/internalClusterTest/java/org/elasticsearch/plugins/IndexFoldersDeletionListenerIT.java
index 7f44fe47a19..8490e0d6c47 100644
--- a/server/src/internalClusterTest/java/org/elasticsearch/plugins/IndexFoldersDeletionListenerIT.java
+++ b/server/src/internalClusterTest/java/org/elasticsearch/plugins/IndexFoldersDeletionListenerIT.java
@@ -325,7 +325,7 @@ public class IndexFoldersDeletionListenerIT extends ESIntegTestCase {
         public List<IndexFoldersDeletionListener> getIndexFoldersDeletionListeners() {
             return List.of(new IndexFoldersDeletionListener() {
                 @Override
-                public void beforeIndexFoldersDeleted(Index index, IndexSettings indexSettings, Path[] indexPaths) {
+                public void beforeIndexFoldersDeleted(Index index, IndexSettings indexSettings) {
                     deletedIndices.add(index);
                 }
 
diff --git a/server/src/main/java/org/elasticsearch/env/NodeEnvironment.java b/server/src/main/java/org/elasticsearch/env/NodeEnvironment.java
index b0686adf8cc..d970fe138e7 100644
--- a/server/src/main/java/org/elasticsearch/env/NodeEnvironment.java
+++ b/server/src/main/java/org/elasticsearch/env/NodeEnvironment.java
@@ -670,7 +670,7 @@ public final class NodeEnvironment  implements Closeable {
         Index index,
         long lockTimeoutMS,
         IndexSettings indexSettings,
-        Consumer<Path[]> listener
+        Consumer<Path> listener
     ) throws IOException, ShardLockObtainFailedException {
         final List<ShardLock> locks = lockAllForIndex(index, indexSettings, "deleting index directory", lockTimeoutMS);
         try {
@@ -687,15 +687,15 @@ public final class NodeEnvironment  implements Closeable {
      * @param index the index to delete
      * @param indexSettings settings for the index being deleted
      */
-    public void deleteIndexDirectoryUnderLock(Index index, IndexSettings indexSettings, Consumer<Path[]> listener) throws IOException {
+    public void deleteIndexDirectoryUnderLock(Index index, IndexSettings indexSettings, Consumer<Path> listener) throws IOException {
         final Path indexPath = indexPath(index);
         logger.trace("deleting index {} directory: [{}]", index, indexPath);
-        listener.accept(new Path[] { indexPath });
+        listener.accept(indexPath);
         IOUtils.rm(indexPath);
         if (indexSettings.hasCustomDataPath()) {
             Path customLocation = resolveIndexCustomLocation(indexSettings.customDataPath(), index.getUUID());
             logger.trace("deleting custom index {} directory [{}]", index, customLocation);
-            listener.accept(new Path[]{customLocation});
+            listener.accept(customLocation);
             IOUtils.rm(customLocation);
         }
     }
diff --git a/server/src/main/java/org/elasticsearch/indices/IndicesService.java b/server/src/main/java/org/elasticsearch/indices/IndicesService.java
index 786db1990a0..0e0f19bc49b 100644
--- a/server/src/main/java/org/elasticsearch/indices/IndicesService.java
+++ b/server/src/main/java/org/elasticsearch/indices/IndicesService.java
@@ -921,7 +921,7 @@ public class IndicesService extends AbstractLifecycleComponent
             if (predicate.apply(index, indexSettings)) {
                 // its safe to delete all index metadata and shard data
                 nodeEnv.deleteIndexDirectorySafe(index, 0, indexSettings,
-                    paths -> indexFoldersDeletionListeners.beforeIndexFoldersDeleted(index, indexSettings, paths));
+                    paths -> indexFoldersDeletionListeners.beforeIndexFoldersDeleted(index, indexSettings));
             }
             success = true;
         } catch (ShardLockObtainFailedException ex) {
@@ -1216,7 +1216,7 @@ public class IndicesService extends AbstractLifecycleComponent
                             logger.debug("{} deleting index store reason [{}]", index, "pending delete");
                             try {
                                 nodeEnv.deleteIndexDirectoryUnderLock(index, indexSettings,
-                                    paths -> indexFoldersDeletionListeners.beforeIndexFoldersDeleted(index, indexSettings, paths));
+                                    paths -> indexFoldersDeletionListeners.beforeIndexFoldersDeleted(index, indexSettings));
                                 iterator.remove();
                             } catch (IOException ex) {
                                 logger.debug(() -> new ParameterizedMessage("{} retry pending delete", index), ex);
diff --git a/server/src/main/java/org/elasticsearch/indices/store/CompositeIndexFoldersDeletionListener.java b/server/src/main/java/org/elasticsearch/indices/store/CompositeIndexFoldersDeletionListener.java
index 16ea2601e48..7d9142db8c1 100644
--- a/server/src/main/java/org/elasticsearch/indices/store/CompositeIndexFoldersDeletionListener.java
+++ b/server/src/main/java/org/elasticsearch/indices/store/CompositeIndexFoldersDeletionListener.java
@@ -30,10 +30,10 @@ public class CompositeIndexFoldersDeletionListener implements IndexStorePlugin.I
     }
 
     @Override
-    public void beforeIndexFoldersDeleted(Index index, IndexSettings indexSettings, Path[] indexPaths) {
+    public void beforeIndexFoldersDeleted(Index index, IndexSettings indexSettings) {
         for (IndexStorePlugin.IndexFoldersDeletionListener listener : listeners) {
             try {
-                listener.beforeIndexFoldersDeleted(index, indexSettings, indexPaths);
+                listener.beforeIndexFoldersDeleted(index, indexSettings);
             } catch (Exception e) {
                 assert false : new AssertionError(e);
                 throw e;
diff --git a/server/src/main/java/org/elasticsearch/plugins/IndexStorePlugin.java b/server/src/main/java/org/elasticsearch/plugins/IndexStorePlugin.java
index 36b644b882f..f116a9a833b 100644
--- a/server/src/main/java/org/elasticsearch/plugins/IndexStorePlugin.java
+++ b/server/src/main/java/org/elasticsearch/plugins/IndexStorePlugin.java
@@ -88,9 +88,8 @@ public interface IndexStorePlugin {
          *
          * @param index         the {@link Index} of the index whose folders are going to be deleted
          * @param indexSettings settings for the index whose folders are going to be deleted
-         * @param indexPaths    the paths of the folders that are going to be deleted
          */
-        void beforeIndexFoldersDeleted(Index index, IndexSettings indexSettings, Path[] indexPaths);
+        void beforeIndexFoldersDeleted(Index index, IndexSettings indexSettings);
 
         /**
          * Invoked before the folders of a shard are deleted from disk. The list of folders contains {@link Path}s that may or may not
diff --git a/server/src/test/java/org/elasticsearch/env/NodeEnvironmentTests.java b/server/src/test/java/org/elasticsearch/env/NodeEnvironmentTests.java
index d8a10232420..44ed1e95ff3 100644
--- a/server/src/test/java/org/elasticsearch/env/NodeEnvironmentTests.java
+++ b/server/src/test/java/org/elasticsearch/env/NodeEnvironmentTests.java
@@ -263,9 +263,9 @@ public class NodeEnvironmentTests extends ESTestCase {
         start.countDown();
         blockLatch.await();
 
-        final SetOnce<Path[]> listener = new SetOnce<>();
+        final SetOnce<Path> listener = new SetOnce<>();
         env.deleteIndexDirectorySafe(index, 5000, idxSettings, listener::set);
-        assertThat(listener.get()[0], equalTo(env.indexPath(index)));
+        assertThat(listener.get(), equalTo(env.indexPath(index)));
         assertNull(threadException.get());
 
         path = env.indexPath(index);
diff --git a/server/src/test/java/org/elasticsearch/index/IndexModuleTests.java b/server/src/test/java/org/elasticsearch/index/IndexModuleTests.java
index 879943ad8cf..b46b46a9b5e 100644
--- a/server/src/test/java/org/elasticsearch/index/IndexModuleTests.java
+++ b/server/src/test/java/org/elasticsearch/index/IndexModuleTests.java
@@ -122,7 +122,7 @@ public class IndexModuleTests extends ESTestCase {
 
     private IndexStorePlugin.IndexFoldersDeletionListener indexDeletionListener = new IndexStorePlugin.IndexFoldersDeletionListener() {
         @Override
-        public void beforeIndexFoldersDeleted(Index index, IndexSettings indexSettings, Path[] indexPaths) {
+        public void beforeIndexFoldersDeleted(Index index, IndexSettings indexSettings) {
         }
 
         @Override
diff --git a/x-pack/plugin/searchable-snapshots/src/main/java/org/elasticsearch/xpack/searchablesnapshots/allocation/SearchableSnapshotIndexFoldersDeletionListener.java b/x-pack/plugin/searchable-snapshots/src/main/java/org/elasticsearch/xpack/searchablesnapshots/allocation/SearchableSnapshotIndexFoldersDeletionListener.java
index 3833b402364..c8a6762ec42 100644
--- a/x-pack/plugin/searchable-snapshots/src/main/java/org/elasticsearch/xpack/searchablesnapshots/allocation/SearchableSnapshotIndexFoldersDeletionListener.java
+++ b/x-pack/plugin/searchable-snapshots/src/main/java/org/elasticsearch/xpack/searchablesnapshots/allocation/SearchableSnapshotIndexFoldersDeletionListener.java
@@ -45,7 +45,7 @@ public class SearchableSnapshotIndexFoldersDeletionListener implements IndexStor
     }
 
     @Override
-    public void beforeIndexFoldersDeleted(Index index, IndexSettings indexSettings, Path[] indexPaths) {
+    public void beforeIndexFoldersDeleted(Index index, IndexSettings indexSettings) {
         if (SearchableSnapshotsConstants.isSearchableSnapshotStore(indexSettings.getSettings())) {
             for (int shard = 0; shard < indexSettings.getNumberOfShards(); shard++) {
                 markShardAsEvictedInCache(new ShardId(index, shard), indexSettings);

[rjernst]

I plan to change all of these consumers in a followup. There are several similar ones.