Java tutorial
/* * Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved. * * This program and the accompanying materials are made available under the * terms of the Eclipse Public License v1.0 which accompanies this distribution, * and is available at http://www.eclipse.org/legal/epl-v10.html */ package org.opendaylight.controller.sal.binding.codegen.impl; import com.google.common.util.concurrent.ForwardingBlockingQueue; import com.google.common.util.concurrent.ListeningExecutorService; import com.google.common.util.concurrent.MoreExecutors; import com.google.common.util.concurrent.ThreadFactoryBuilder; import java.util.concurrent.BlockingQueue; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.LinkedBlockingQueue; import java.util.concurrent.RejectedExecutionException; import java.util.concurrent.RejectedExecutionHandler; import java.util.concurrent.ThreadFactory; import java.util.concurrent.ThreadPoolExecutor; import java.util.concurrent.TimeUnit; import javassist.ClassPool; import org.apache.commons.lang3.StringUtils; import org.opendaylight.yangtools.sal.binding.generator.util.JavassistUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; public class SingletonHolder { private static final Logger logger = LoggerFactory.getLogger(SingletonHolder.class); public static final ClassPool CLASS_POOL = ClassPool.getDefault(); public static final JavassistUtils JAVASSIST = JavassistUtils.forClassPool(CLASS_POOL); public static final int CORE_NOTIFICATION_THREADS = 4; public static final int MAX_NOTIFICATION_THREADS = 32; // block caller thread after MAX_NOTIFICATION_THREADS + MAX_NOTIFICATION_QUEUE_SIZE pending notifications public static final int MAX_NOTIFICATION_QUEUE_SIZE = 1000; public static final int NOTIFICATION_THREAD_LIFE = 15; private static final String NOTIFICATION_QUEUE_SIZE_PROPERTY = "mdsal.notificationqueue.size"; private static ListeningExecutorService NOTIFICATION_EXECUTOR = null; private static ListeningExecutorService COMMIT_EXECUTOR = null; private static ListeningExecutorService CHANGE_EVENT_EXECUTOR = null; /** * @deprecated This method is only used from configuration modules and thus callers of it * should use service injection to make the executor configurable. */ @Deprecated public static synchronized ListeningExecutorService getDefaultNotificationExecutor() { if (NOTIFICATION_EXECUTOR == null) { int queueSize = MAX_NOTIFICATION_QUEUE_SIZE; final String queueValue = System.getProperty(NOTIFICATION_QUEUE_SIZE_PROPERTY); if (StringUtils.isNotBlank(queueValue)) { try { queueSize = Integer.parseInt(queueValue); logger.trace("Queue size was set to {}", queueSize); } catch (final NumberFormatException e) { logger.warn("Cannot parse {} as set by {}, using default {}", queueValue, NOTIFICATION_QUEUE_SIZE_PROPERTY, queueSize); } } // Overriding the queue: // ThreadPoolExecutor would not create new threads if the queue is not full, thus adding // occurs in RejectedExecutionHandler. // This impl saturates threadpool first, then queue. When both are full caller will get blocked. final BlockingQueue<Runnable> delegate = new LinkedBlockingQueue<>(queueSize); final BlockingQueue<Runnable> queue = new ForwardingBlockingQueue<Runnable>() { @Override protected BlockingQueue<Runnable> delegate() { return delegate; } @Override public boolean offer(final Runnable r) { // ThreadPoolExecutor will spawn a new thread after core size is reached only // if the queue.offer returns false. return false; } }; final ThreadFactory factory = new ThreadFactoryBuilder().setDaemon(true) .setNameFormat("md-sal-binding-notification-%d").build(); final ThreadPoolExecutor executor = new ThreadPoolExecutor(CORE_NOTIFICATION_THREADS, MAX_NOTIFICATION_THREADS, NOTIFICATION_THREAD_LIFE, TimeUnit.SECONDS, queue, factory, new RejectedExecutionHandler() { // if the max threads are met, then it will raise a rejectedExecution. We then push to the queue. @Override public void rejectedExecution(final Runnable r, final ThreadPoolExecutor executor) { try { executor.getQueue().put(r); } catch (final InterruptedException e) { throw new RejectedExecutionException("Interrupted while waiting on the queue", e); } } }); NOTIFICATION_EXECUTOR = MoreExecutors.listeningDecorator(executor); } return NOTIFICATION_EXECUTOR; } /** * @deprecated This method is only used from configuration modules and thus callers of it * should use service injection to make the executor configurable. */ @Deprecated public static synchronized ListeningExecutorService getDefaultCommitExecutor() { if (COMMIT_EXECUTOR == null) { final ThreadFactory factory = new ThreadFactoryBuilder().setDaemon(true) .setNameFormat("md-sal-binding-commit-%d").build(); /* * FIXME: this used to be newCacheThreadPool(), but MD-SAL does not have transaction * ordering guarantees, which means that using a concurrent threadpool results * in application data being committed in random order, potentially resulting * in inconsistent data being present. Once proper primitives are introduced, * concurrency can be reintroduced. */ final ExecutorService executor = Executors.newSingleThreadExecutor(factory); COMMIT_EXECUTOR = MoreExecutors.listeningDecorator(executor); } return COMMIT_EXECUTOR; } public static ExecutorService getDefaultChangeEventExecutor() { if (CHANGE_EVENT_EXECUTOR == null) { final ThreadFactory factory = new ThreadFactoryBuilder().setDaemon(true) .setNameFormat("md-sal-binding-change-%d").build(); /* * FIXME: this used to be newCacheThreadPool(), but MD-SAL does not have transaction * ordering guarantees, which means that using a concurrent threadpool results * in application data being committed in random order, potentially resulting * in inconsistent data being present. Once proper primitives are introduced, * concurrency can be reintroduced. */ final ExecutorService executor = Executors.newSingleThreadExecutor(factory); CHANGE_EVENT_EXECUTOR = MoreExecutors.listeningDecorator(executor); } return CHANGE_EVENT_EXECUTOR; } }