Add missing logic in untangle engine ctor backport

This commit adds missing logic during backporting the untangle engine
constructor PR (#28245). These minor logic helps to handle an old indices
which do not have all 6.x commit tags such as max_unsafe_autoid_timestamp
or historyUUID or sequence numbers.

Author: dnhatn

server/src/main/java/org/elasticsearch/index/shard/LocalShardSnapshot.java

@@ -34,6 +34,7 @@
 import java.io.Closeable;
 import java.io.IOException;
 import java.util.Collection;
+import java.util.Map;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 final class LocalShardSnapshot implements Closeable {
@@ -66,7 +67,8 @@ long maxSeqNo() {
     }
 
     long maxUnsafeAutoIdTimestamp() {
-        return Long.parseLong(shard.getEngine().commitStats().getUserData().get(InternalEngine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID));
+        final Map<String, String> commitUserData = shard.getEngine().commitStats().getUserData();
+        return Long.parseLong(commitUserData.getOrDefault(InternalEngine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID, "-1"));
     }
 
     Directory getSnapshotDirectory() {

server/src/main/java/org/elasticsearch/index/shard/StoreRecovery.java

@@ -396,10 +396,12 @@ private void internalRecoverFromStore(IndexShard indexShard) throws IndexShardRe
                 final String translogUUID = Translog.createEmptyTranslog(indexShard.shardPath().resolveTranslog(), maxSeqNo, shardId);
                 store.associateIndexWithNewTranslog(translogUUID);
             } else if (indexShouldExists) {
-                // since we recover from local, just fill the files and size
                 if (indexShard.indexSettings().getIndexVersionCreated().before(Version.V_6_0_0_rc1)) {
-                    store.ensureIndexHasHistoryUUIDAndSeqNo();
+                    if (store.ensureIndexHasHistoryUUIDAndSeqNo()) {
+                        si = store.readLastCommittedSegmentsInfo(); // new commit is flushed - refresh SegmentInfo.
+                    }
                 }
+                // since we recover from local, just fill the files and size
                 try {
                     final RecoveryState.Index index = recoveryState.getIndex();
                     if (si != null) {

server/src/main/java/org/elasticsearch/index/store/Store.java

@@ -1517,13 +1517,14 @@ public void associateIndexWithNewTranslog(final String translogUUID) throws IOEx
         }
     }
 
-
     /**
-     * A 5.x index does not have either historyUUDID or sequence number markers as both markers are introduced in 6.0+.
+     * A 5.x index does not have either historyUUDID or sequence number markers as these markers are introduced in 6.0+.
      * This method should be called only in local store recovery or file-based recovery to ensure an index has proper
      * historyUUID and sequence number markers before opening an engine.
+     *
+     * @return <code>true</code> if a new commit is flushed, otherwise return false
      */
-    public void ensureIndexHasHistoryUUIDAndSeqNo() throws IOException {
+    public boolean ensureIndexHasHistoryUUIDAndSeqNo() throws IOException {
         metadataLock.writeLock().lock();
         try (IndexWriter writer = newIndexWriter(IndexWriterConfig.OpenMode.APPEND, directory, null)) {
             final Map<String, String> userData = getUserData(writer);
@@ -1539,10 +1540,12 @@ public void ensureIndexHasHistoryUUIDAndSeqNo() throws IOException {
             }
             if (maps.isEmpty() == false) {
                 updateCommitData(writer, maps);
+                return true;
             }
         } finally {
             metadataLock.writeLock().unlock();
         }
+        return false;
     }
 
     /**