add yet another test

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

@@ -556,7 +556,7 @@ public class IndexShard extends AbstractIndexShardComponent {
     /** Writes all indexing changes to disk and opens a new searcher reflecting all changes.  This can throw {@link EngineClosedException}. */
     public void refresh(String source) {
         verifyNotClosed();
-//        if (getEngine().refreshNeeded()) {
+        if (getEngine().refreshNeeded()) {
             if (canIndex()) {
                 long bytes = getEngine().getIndexBufferRAMBytesUsed();
                 writingBytes.addAndGet(bytes);
@@ -575,7 +575,7 @@ public class IndexShard extends AbstractIndexShardComponent {
                 getEngine().refresh(source);
                 refreshMetric.inc(System.nanoTime() - time);
             }
-//        }
+        }
     }
 
     /** Returns how many bytes we are currently moving from heap to disk */

core/src/test/java/org/elasticsearch/index/IndexServiceTests.java

@@ -322,6 +322,13 @@ public class IndexServiceTests extends ESSingleNodeTestCase {
         assertBusy(() -> {
             assertFalse(shard.getTranslog().syncNeeded());
         });
+    }
 
+    public void testNoFsyncTaskIfDisabled() {
+        Settings settings = Settings.builder()
+            .put(IndexSettings.INDEX_TRANSLOG_SYNC_INTERVAL, "0ms") // disable
+            .build();
+        IndexService indexService = createIndex("test", settings);
+        assertNull(indexService.getFsyncTask());
     }
 }