Add a shutdown hook to executor service in JerseySupport (#2505)

* Add a shutdown hook to executor service JerseySupport. This should prevent threads in this executor to attempt reads/writes after Netty's executor is also down.

Signed-off-by: Santiago Pericasgeertsen <santiago.pericasgeertsen@oracle.com>

* Use shutdownNow instead.

Signed-off-by: Santiago Pericasgeertsen <santiago.pericasgeertsen@oracle.com>

webserver/jersey/src/main/java/io/helidon/webserver/jersey/JerseySupport.java

@@ -106,6 +106,7 @@ public class JerseySupport implements Service {
     private final ExecutorService service;
     private final JerseyHandler handler = new JerseyHandler();
     private final HelidonJerseyContainer container;
+    private final Thread serviceShutdownHook;
 
     /**
      * Creates a Jersey Support based on the provided JAX-RS application.
@@ -121,6 +122,10 @@ public class JerseySupport implements Service {
                 : getDefaultThreadPool(builder.config);
         this.service = Contexts.wrap(executorService);
 
+        // Prevents reads/writes after Netty event loops are shutdown
+        serviceShutdownHook = new Thread(service::shutdownNow);
+        Runtime.getRuntime().addShutdownHook(serviceShutdownHook);
+
         // make sure we have a wrapped async executor as well
         if (builder.asyncExecutorService == null) {
             // create a new one from configuration
@@ -140,6 +145,15 @@ public class JerseySupport implements Service {
         appHandler.onStartup(container);
     }
 
+    /**
+     * Returns registered shutdown hook for testing purposes.
+     *
+     * @return service shutdown hook
+     */
+    Thread serviceShutdownHook() {
+        return serviceShutdownHook;
+    }
+
     private static synchronized ExecutorService getDefaultThreadPool(Config config) {
         if (DEFAULT_THREAD_POOL.get() == null) {
             Config executorConfig = config.get("executor-service");

webserver/jersey/src/test/java/io/helidon/webserver/jersey/JerseySupportShutdownTest.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2020 Oracle and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.helidon.webserver.jersey;
+
+import org.junit.jupiter.api.Test;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.CoreMatchers.notNullValue;
+
+public class JerseySupportShutdownTest {
+
+    @Test
+    public void shutdownHook() {
+        JerseySupport jerseySupport = JerseySupport.builder().build();
+        assertThat(jerseySupport.serviceShutdownHook(), notNullValue());
+        boolean exists = Runtime.getRuntime().removeShutdownHook(jerseySupport.serviceShutdownHook());
+        assertThat(exists, is(true));
+    }
+}