Fix flaky test SegmentReplicationWithNodeToNodeIndexShardTests#testRe…

…plicaClosesWhileReplicating_AfterGetCheckpoint (#12695) (#12741)

This fixes a race condition in the test where the primary shard will still have an open file ref while shutting down.
This happens because we are fetching file refs inside the resolveCheckpointInfoResponseListener method right  after calling beforeIndexShardClosed.
BeforeIndexShardClosed will resolve replication listeners immediately and leave a possibility
of the primary attempting shut down before those refs are closed. We can resolve this using latches, but this test really doesn't need to simulate a primary response at all so removed it entirely.


(cherry picked from commit 5e2034c)

Signed-off-by: Marc Handalian <[email protected]>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

server/src/test/java/org/opensearch/index/shard/SegmentReplicationWithNodeToNodeIndexShardTests.java

@@ -110,7 +110,6 @@ public void testReplicaClosesWhileReplicating_AfterGetCheckpoint() throws Except
             IndexShard primary = shards.getPrimary();
             final IndexShard replica = shards.getReplicas().get(0);
 
-            final int numDocs = shards.indexDocs(randomInt(10));
             primary.refresh("Test");
 
             final SegmentReplicationSourceFactory sourceFactory = mock(SegmentReplicationSourceFactory.class);
@@ -124,7 +123,6 @@ public void getCheckpointMetadata(
                 ) {
                     // trigger a cancellation by closing the replica.
                     targetService.beforeIndexShardClosed(replica.shardId, replica, Settings.EMPTY);
-                    resolveCheckpointInfoResponseListener(listener, primary);
                 }
 
                 @Override
@@ -141,7 +139,6 @@ public void getSegmentFiles(
             };
             when(sourceFactory.get(any())).thenReturn(source);
             startReplicationAndAssertCancellation(replica, primary, targetService);
-
             shards.removeReplica(replica);
             closeShards(replica);
         }