Use withEngine in IndexShard#seqNoStats

Author: tlrx

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

@@ -1386,7 +1386,7 @@ public CommitStats commitStats() {
      * @throws AlreadyClosedException if shard is closed
      */
     public SeqNoStats seqNoStats() {
-        return getEngine().getSeqNoStats(replicationTracker.getGlobalCheckpoint());
+        return withEngine(engine -> engine.getSeqNoStats(getLastKnownGlobalCheckpoint()));
     }
 
     public IndexingStats indexingStats() {

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/action/ShardChangesAction.java

@@ -403,13 +403,13 @@ protected void asyncShardOperation(final Request request, final ShardId shardId,
             throws IOException {
             final IndexService indexService = indicesService.indexServiceSafe(request.getShard().getIndex());
             final IndexShard indexShard = indexService.getShard(request.getShard().id());
-            final SeqNoStats seqNoStats = indexShard.seqNoStats();
+            final long lastKnownGlobalCheckpoint = indexShard.getLastKnownGlobalCheckpoint();
 
-            if (request.getFromSeqNo() > seqNoStats.getGlobalCheckpoint()) {
+            if (request.getFromSeqNo() > lastKnownGlobalCheckpoint) {
                 logger.trace(
                     "{} waiting for global checkpoint advancement from [{}] to [{}]",
                     shardId,
-                    seqNoStats.getGlobalCheckpoint(),
+                    lastKnownGlobalCheckpoint,
                     request.getFromSeqNo()
                 );
                 indexShard.addGlobalCheckpointListener(request.getFromSeqNo(), new GlobalCheckpointListeners.GlobalCheckpointListener() {