add test verifying that refresh does not block closing

Author: dnhatn

server/src/test/java/org/elasticsearch/index/engine/InternalEngineTests.java

@@ -136,6 +136,7 @@
 import org.elasticsearch.indices.breaker.NoneCircuitBreakerService;
 import org.elasticsearch.test.IndexSettingsModule;
 import org.elasticsearch.test.VersionUtils;
+import org.elasticsearch.threadpool.ThreadPool;
 import org.hamcrest.MatcherAssert;
 
 import java.io.Closeable;
@@ -6137,4 +6138,41 @@ public void afterRefresh(boolean didRefresh) {
             }
         }
     }
+
+    public void testRefreshDoesNotBlockClosing() throws Exception {
+        final CountDownLatch refreshStarted = new CountDownLatch(1);
+        final CountDownLatch engineClosed = new CountDownLatch(1);
+        final ReferenceManager.RefreshListener refreshListener = new ReferenceManager.RefreshListener() {
+
+            @Override
+            public void beforeRefresh() {
+                refreshStarted.countDown();
+                try {
+                    engineClosed.await();
+                } catch (InterruptedException e) {
+                    throw new AssertionError(e);
+                }
+            }
+
+            @Override
+            public void afterRefresh(boolean didRefresh) {
+                assertFalse(didRefresh);
+            }
+        };
+        try (Store store = createStore()) {
+            final EngineConfig config = config(defaultSettings, store, createTempDir(), newMergePolicy(), null,
+                refreshListener, null, null, engine.config().getCircuitBreakerService());
+            try (InternalEngine engine = createEngine(config)) {
+                if (randomBoolean()) {
+                    engine.index(indexForDoc(createParsedDoc("id", null)));
+                }
+                threadPool.executor(ThreadPool.Names.REFRESH).execute(() ->
+                    expectThrows(AlreadyClosedException.class,
+                        () -> engine.refresh("test", randomFrom(Engine.SearcherScope.values()), true)));
+                refreshStarted.await();
+                engine.close();
+                engineClosed.countDown();
+            }
+        }
+    }
 }