test/org/apache/catalina/loader/TestWebappClassLoaderMemoryLeak.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.catalina.loader;

import java.io.IOException;
import java.util.Timer;
import java.util.TimerTask;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import static org.junit.Assert.fail;

import org.junit.Test;

import org.apache.catalina.Context;
import org.apache.catalina.core.StandardContext;
import org.apache.catalina.startup.Tomcat;
import org.apache.catalina.startup.TomcatBaseTest;

public class TestWebappClassLoaderMemoryLeak extends TomcatBaseTest {

    @Test
    public void testTimerThreadLeak() throws Exception {
        Tomcat tomcat = getTomcatInstance();

        // No file system docBase required
        Context ctx = tomcat.addContext("", null);

        if (ctx instanceof StandardContext) {
            ((StandardContext) ctx).setClearReferencesStopTimerThreads(true);
        }

        Tomcat.addServlet(ctx, "taskServlet", new TaskServlet());
        ctx.addServletMappingDecoded("/", "taskServlet");

        tomcat.start();

        // This will trigger the timer & thread creation
        getUrl("http://localhost:" + getPort() + "/");

        // Stop the context
        ctx.stop();

        Thread[] threads = getThreads();
        for (Thread thread : threads) {
            if (thread != null && thread.isAlive() &&
                    TaskServlet.TIMER_THREAD_NAME.equals(thread.getName())) {
                thread.join(5000);
                if (thread.isAlive()) {
                    fail("Timer thread still running");
                }
            }
        }
    }

    /*
     * Get the set of current threads as an array.
     * Copied from WebappClassLoaderBase
     */
    private Thread[] getThreads() {
        // Get the current thread group
        ThreadGroup tg = Thread.currentThread( ).getThreadGroup( );
        // Find the root thread group
        while (tg.getParent() != null) {
            tg = tg.getParent();
        }

        int threadCountGuess = tg.activeCount() + 50;
        Thread[] threads = new Thread[threadCountGuess];
        int threadCountActual = tg.enumerate(threads);
        // Make sure we don't miss any threads
        while (threadCountActual == threadCountGuess) {
            threadCountGuess *=2;
            threads = new Thread[threadCountGuess];
            // Note tg.enumerate(Thread[]) silently ignores any threads that
            // can't fit into the array
            threadCountActual = tg.enumerate(threads);
        }

        return threads;
    }

    private static final class TaskServlet extends HttpServlet {

        private static final long serialVersionUID = 1L;
        private static final String TIMER_THREAD_NAME = "leaked-thread";

        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException {
            Timer timer = new Timer(TIMER_THREAD_NAME);
            timer.schedule(new LocalTask(), 0, 10000);
        }

    }

    private static final class LocalTask extends TimerTask {

        @Override
        public void run() {
            // Doesn't actually need to do anything.
        }

    }
}