Acquire seacher on closing engine should throw AlreadyClosedException

Closes elastic#33330

Author: dnhatn

server/src/main/java/org/elasticsearch/index/engine/InternalEngine.java

@@ -1994,12 +1994,14 @@ protected final void closeNoLock(String reason, CountDownLatch closedLatch) {
 
     @Override
     public Searcher acquireSearcher(String source, SearcherScope scope) {
-        /* Acquire order here is store -> manager since we need
-         * to make sure that the store is not closed before
-         * the searcher is acquired. */
-        store.incRef();
-        Releasable releasable = store::decRef;
+        ensureOpen();
+        Releasable releasable = null;
         try {
+            /* Acquire order here is store -> manager since we need
+             * to make sure that the store is not closed before
+             * the searcher is acquired. */
+            store.incRef();
+            releasable = store::decRef;
             final ReferenceManager<IndexSearcher> referenceManager;
             switch (scope) {
                 case INTERNAL:

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

@@ -5020,6 +5020,11 @@ public void testLastRefreshCheckpoint() throws Exception {
         assertThat(engine.lastRefreshedCheckpoint(), equalTo(engine.getLocalCheckpoint()));
     }
 
+    public void testAcquireSearcherOnClosingEngine() throws Exception {
+        engine.close();
+        expectThrows(AlreadyClosedException.class, () -> engine.acquireSearcher("test"));
+    }
+
     private static void trimUnsafeCommits(EngineConfig config) throws IOException {
         final Store store = config.getStore();
         final TranslogConfig translogConfig = config.getTranslogConfig();