Java tutorial
/* * * 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.hadoop.hbase.util; import static org.junit.Assert.assertTrue; import java.util.Map; import java.util.Random; import java.util.concurrent.Callable; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ExecutorCompletionService; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; import java.util.concurrent.TimeUnit; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.hbase.MediumTests; import org.junit.Test; import org.junit.experimental.categories.Category; @Category(MediumTests.class) // Medium as it creates 100 threads; seems better to run it isolated public class TestIdLock { private static final Log LOG = LogFactory.getLog(TestIdLock.class); private static final int NUM_IDS = 16; private static final int NUM_THREADS = 128; private static final int NUM_SECONDS = 15; private IdLock idLock = new IdLock(); private Map<Long, String> idOwner = new ConcurrentHashMap<Long, String>(); private class IdLockTestThread implements Callable<Boolean> { private String clientId; public IdLockTestThread(String clientId) { this.clientId = clientId; } @Override public Boolean call() throws Exception { Thread.currentThread().setName(clientId); Random rand = new Random(); long endTime = System.currentTimeMillis() + NUM_SECONDS * 1000; while (System.currentTimeMillis() < endTime) { long id = rand.nextInt(NUM_IDS); IdLock.Entry lockEntry = idLock.getLockEntry(id); try { int sleepMs = 1 + rand.nextInt(4); String owner = idOwner.get(id); if (owner != null) { LOG.error("Id " + id + " already taken by " + owner + ", " + clientId + " failed"); return false; } idOwner.put(id, clientId); Thread.sleep(sleepMs); idOwner.remove(id); } finally { idLock.releaseLockEntry(lockEntry); } } return true; } } @Test public void testMultipleClients() throws Exception { ExecutorService exec = Executors.newFixedThreadPool(NUM_THREADS); try { ExecutorCompletionService<Boolean> ecs = new ExecutorCompletionService<Boolean>(exec); for (int i = 0; i < NUM_THREADS; ++i) ecs.submit(new IdLockTestThread("client_" + i)); for (int i = 0; i < NUM_THREADS; ++i) { Future<Boolean> result = ecs.take(); assertTrue(result.get()); } idLock.assertMapEmpty(); } finally { exec.shutdown(); exec.awaitTermination(5000, TimeUnit.MILLISECONDS); } } }