[Remote Segment Store] Make metadata file immutable

server/src/internalClusterTest/java/org/opensearch/indices/replication/SegmentReplicationIT.java

@@ -800,6 +800,7 @@ public void testReplicaHasDiffFilesThanPrimary() throws Exception {
     public void testPressureServiceStats() throws Exception {
         final String primaryNode = internalCluster().startDataOnlyNode();
         createIndex(INDEX_NAME);
+        ensureYellow(INDEX_NAME);
         final String replicaNode = internalCluster().startDataOnlyNode();
         ensureGreen(INDEX_NAME);
 

server/src/internalClusterTest/java/org/opensearch/remotestore/RemoteStoreIT.java

@@ -320,6 +320,6 @@ public void testStaleCommitDeletionWithoutInvokeFlush() throws Exception {
             .get()
             .getSetting(INDEX_NAME, IndexMetadata.SETTING_INDEX_UUID);
         Path indexPath = Path.of(String.valueOf(absolutePath), indexUUID, "/0/segments/metadata");
-        assertEquals(1, getFileCount(indexPath));
+        assertEquals(numberOfIterations, getFileCount(indexPath));
     }
 }

server/src/main/java/org/opensearch/index/shard/RemoteStoreRefreshListener.java

@@ -349,11 +349,13 @@ void uploadMetadata(Collection<String> localSegmentsPostRefresh, SegmentInfos se
         userData.put(SequenceNumbers.MAX_SEQ_NO, Long.toString(maxSeqNo));
         segmentInfosSnapshot.setUserData(userData, false);
 
+        long translogGeneration = indexShard.getEngine().translogManager().getTranslogGeneration().translogFileGeneration;
         remoteDirectory.uploadMetadata(
             localSegmentsPostRefresh,
             segmentInfosSnapshot,
             storeDirectory,
-            indexShard.getOperationPrimaryTerm()
+            indexShard.getOperationPrimaryTerm(),
+            translogGeneration
         );
     }
 

server/src/main/java/org/opensearch/index/store/RemoteDirectory.java

@@ -13,17 +13,24 @@
 import org.apache.lucene.store.IndexInput;
 import org.apache.lucene.store.IndexOutput;
 import org.apache.lucene.store.Lock;
+import org.opensearch.action.ActionListener;
+import org.opensearch.action.LatchedActionListener;
 import org.opensearch.common.blobstore.BlobContainer;
 import org.opensearch.common.blobstore.BlobMetadata;
 
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.file.NoSuchFileException;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.stream.Collectors;
 
 /**
  * A {@code RemoteDirectory} provides an abstraction layer for storing a list of files to a remote store.
@@ -61,6 +68,40 @@ public Collection<String> listFilesByPrefix(String filenamePrefix) throws IOExce
         return blobContainer.listBlobsByPrefix(filenamePrefix).keySet();
     }
 
+    public List<String> listFilesByPrefixInLexicographicOrder(String filenamePrefix, int limit) throws IOException {
+        List<String> sortedBlobList = new ArrayList<>();
+        AtomicReference<Exception> exception = new AtomicReference<>();
+        final CountDownLatch latch = new CountDownLatch(1);
+        LatchedActionListener<List<BlobMetadata>> actionListener = new LatchedActionListener<>(new ActionListener<>() {
+            @Override
+            public void onResponse(List<BlobMetadata> blobMetadata) {
+                sortedBlobList.addAll(blobMetadata.stream().map(BlobMetadata::name).collect(Collectors.toList()));
+            }
+
+            @Override
+            public void onFailure(Exception e) {
+                exception.set(e);
+            }
+        }, latch);
+
+        try {
+            blobContainer.listBlobsByPrefixInSortedOrder(
+                filenamePrefix,
+                limit,
+                BlobContainer.BlobNameSortOrder.LEXICOGRAPHIC,
+                actionListener
+            );
+            latch.await();
+        } catch (InterruptedException e) {
+            throw new IOException("Exception in listFilesByPrefixInLexicographicOrder with prefix: " + filenamePrefix, e);
+        }
+        if (exception.get() != null) {
+            throw new IOException(exception.get());
+        } else {
+            return sortedBlobList;
+        }
+    }
+
     /**
      * Removes an existing file in the directory.
      *