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 java.io.PrintWriter; import java.lang.Thread.UncaughtExceptionHandler; import java.util.concurrent.LinkedBlockingQueue; import java.util.concurrent.ThreadFactory; import java.util.concurrent.ThreadPoolExecutor; import java.util.concurrent.TimeUnit; import java.util.concurrent.atomic.AtomicInteger; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.util.ReflectionUtils; /** * Thread Utility */ @InterfaceAudience.Private public class Threads { protected static final Log LOG = LogFactory.getLog(Threads.class); private static final AtomicInteger poolNumber = new AtomicInteger(1); /** * Utility method that sets name, daemon status and starts passed thread. * @param t thread to run * @return Returns the passed Thread <code>t</code>. */ public static Thread setDaemonThreadRunning(final Thread t) { return setDaemonThreadRunning(t, t.getName()); } /** * Utility method that sets name, daemon status and starts passed thread. * @param t thread to frob * @param name new name * @return Returns the passed Thread <code>t</code>. */ public static Thread setDaemonThreadRunning(final Thread t, final String name) { return setDaemonThreadRunning(t, name, null); } /** * Utility method that sets name, daemon status and starts passed thread. * @param t thread to frob * @param name new name * @param handler A handler to set on the thread. Pass null if want to * use default handler. * @return Returns the passed Thread <code>t</code>. */ public static Thread setDaemonThreadRunning(final Thread t, final String name, final UncaughtExceptionHandler handler) { t.setName(name); if (handler != null) { t.setUncaughtExceptionHandler(handler); } t.setDaemon(true); t.start(); return t; } /** * Shutdown passed thread using isAlive and join. * @param t Thread to shutdown */ public static void shutdown(final Thread t) { shutdown(t, 0); } /** * Shutdown passed thread using isAlive and join. * @param joinwait Pass 0 if we're to wait forever. * @param t Thread to shutdown */ public static void shutdown(final Thread t, final long joinwait) { if (t == null) return; while (t.isAlive()) { try { t.join(joinwait); } catch (InterruptedException e) { LOG.warn(t.getName() + "; joinwait=" + joinwait, e); } } } /** * @param t Waits on the passed thread to die dumping a threaddump every * minute while its up. * @throws InterruptedException */ public static void threadDumpingIsAlive(final Thread t) throws InterruptedException { if (t == null) { return; } while (t.isAlive()) { t.join(60 * 1000); if (t.isAlive()) { ReflectionUtils.printThreadInfo(new PrintWriter(System.out), "Automatic Stack Trace every 60 seconds waiting on " + t.getName()); } } } /** * If interrupted, just prints out the interrupt on STDOUT, resets interrupt and returns * @param millis How long to sleep for in milliseconds. */ public static void sleep(long millis) { try { Thread.sleep(millis); } catch (InterruptedException e) { e.printStackTrace(); Thread.currentThread().interrupt(); } } /** * Sleeps for the given amount of time even if interrupted. Preserves * the interrupt status. * @param msToWait the amount of time to sleep in milliseconds */ public static void sleepWithoutInterrupt(final long msToWait) { long timeMillis = System.currentTimeMillis(); long endTime = timeMillis + msToWait; boolean interrupted = false; while (timeMillis < endTime) { try { Thread.sleep(endTime - timeMillis); } catch (InterruptedException ex) { interrupted = true; } timeMillis = System.currentTimeMillis(); } if (interrupted) { Thread.currentThread().interrupt(); } } /** * Create a new CachedThreadPool with a bounded number as the maximum * thread size in the pool. * * @param maxCachedThread the maximum thread could be created in the pool * @param timeout the maximum time to wait * @param unit the time unit of the timeout argument * @param threadFactory the factory to use when creating new threads * @return threadPoolExecutor the cachedThreadPool with a bounded number * as the maximum thread size in the pool. */ public static ThreadPoolExecutor getBoundedCachedThreadPool(int maxCachedThread, long timeout, TimeUnit unit, ThreadFactory threadFactory) { ThreadPoolExecutor boundedCachedThreadPool = new ThreadPoolExecutor(maxCachedThread, maxCachedThread, timeout, unit, new LinkedBlockingQueue<Runnable>(), threadFactory); // allow the core pool threads timeout and terminate boundedCachedThreadPool.allowCoreThreadTimeOut(true); return boundedCachedThreadPool; } /** * Returns a {@link java.util.concurrent.ThreadFactory} that names each created thread uniquely, * with a common prefix. * @param prefix The prefix of every created Thread's name * @return a {@link java.util.concurrent.ThreadFactory} that names threads */ public static ThreadFactory getNamedThreadFactory(final String prefix) { SecurityManager s = System.getSecurityManager(); final ThreadGroup threadGroup = (s != null) ? s.getThreadGroup() : Thread.currentThread().getThreadGroup(); return new ThreadFactory() { final AtomicInteger threadNumber = new AtomicInteger(1); private final int poolNumber = Threads.poolNumber.getAndIncrement(); final ThreadGroup group = threadGroup; @Override public Thread newThread(Runnable r) { final String name = prefix + "-pool" + poolNumber + "-t" + threadNumber.getAndIncrement(); return new Thread(group, r, name); } }; } /** * Same as {#newDaemonThreadFactory(String, UncaughtExceptionHandler)}, * without setting the exception handler. */ public static ThreadFactory newDaemonThreadFactory(final String prefix) { return newDaemonThreadFactory(prefix, null); } /** * Get a named {@link ThreadFactory} that just builds daemon threads. * @param prefix name prefix for all threads created from the factory * @param handler unhandles exception handler to set for all threads * @return a thread factory that creates named, daemon threads with * the supplied exception handler and normal priority */ public static ThreadFactory newDaemonThreadFactory(final String prefix, final UncaughtExceptionHandler handler) { final ThreadFactory namedFactory = getNamedThreadFactory(prefix); return new ThreadFactory() { @Override public Thread newThread(Runnable r) { Thread t = namedFactory.newThread(r); if (handler != null) { t.setUncaughtExceptionHandler(handler); } if (!t.isDaemon()) { t.setDaemon(true); } if (t.getPriority() != Thread.NORM_PRIORITY) { t.setPriority(Thread.NORM_PRIORITY); } return t; } }; } }