Java tutorial
/* * Copyright (C) 2007-2016 Peter Monks. * 2012 Alain Sahli - Fix for issue 109: http://code.google.com/p/alfresco-bulk-filesystem-import/issues/detail?id=109. * * 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. * * This file is part of an unsupported extension to Alfresco. * */ package org.alfresco.extension.bulkimport.impl; import java.util.concurrent.*; import org.alfresco.extension.bulkimport.util.ThreadPauser; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import static org.alfresco.extension.bulkimport.util.LogUtils.*; /** * This class provides a simplified <code>ThreadPoolExecutor</code> * that uses sensible defaults for the bulk import tool. Note that calls to * <code>execute</code> and <code>submit</code> can block. * * @author Peter Monks (pmonks@gmail.com) */ public class BulkImportThreadPoolExecutor extends ThreadPoolExecutor { private final static Log log = LogFactory.getLog(BulkImportThreadPoolExecutor.class); private final static int DEFAULT_THREAD_POOL_SIZE = Runtime.getRuntime().availableProcessors() * 4; private final static long DEFAULT_KEEP_ALIVE_TIME = 10L; private final static TimeUnit DEFAULT_KEEP_ALIVE_TIME_UNIT = TimeUnit.MINUTES; private final static int DEFAULT_QUEUE_CAPACITY = 100; // Batches private final int queueCapacity; private final ThreadPauser pauser; private final Semaphore queueSemaphore; public BulkImportThreadPoolExecutor(final ThreadPauser pauser, final int threadPoolSize, final int queueCapacity, final long keepAliveTime, final TimeUnit keepAliveTimeUnit) { super(threadPoolSize <= 0 ? DEFAULT_THREAD_POOL_SIZE : threadPoolSize, // Core pool size threadPoolSize <= 0 ? DEFAULT_THREAD_POOL_SIZE : threadPoolSize, // Max pool size (same as core pool size) keepAliveTime <= 0 ? DEFAULT_KEEP_ALIVE_TIME : keepAliveTime, // Keep alive keepAliveTimeUnit == null ? DEFAULT_KEEP_ALIVE_TIME_UNIT : keepAliveTimeUnit, // Keep alive units new LinkedBlockingQueue<Runnable>(), // Queue of maximum size new BulkImportThreadFactory(), // Thread factory new ThreadPoolExecutor.AbortPolicy()); // Rejection handler (shouldn't ever be called, due to the use of a semaphone before task submission) this.queueCapacity = queueCapacity; this.pauser = pauser; final int queuePlusPoolSize = (queueCapacity <= 0 ? DEFAULT_QUEUE_CAPACITY : queueCapacity) + (threadPoolSize <= 0 ? DEFAULT_THREAD_POOL_SIZE : threadPoolSize); this.queueSemaphore = new Semaphore(queuePlusPoolSize); if (debug(log)) debug(log, "Created new bulk import thread pool." + " Thread Pool Size=" + (threadPoolSize <= 0 ? DEFAULT_THREAD_POOL_SIZE : threadPoolSize) + ", Queue Capacity=" + ((queueCapacity <= 0 ? DEFAULT_QUEUE_CAPACITY : queueCapacity) + 2) + ", Keep Alive Time=" + (keepAliveTime <= 0 ? DEFAULT_KEEP_ALIVE_TIME : keepAliveTime) + " " + String.valueOf(keepAliveTimeUnit == null ? DEFAULT_KEEP_ALIVE_TIME_UNIT : keepAliveTimeUnit)); } /** * @see {@link ThreadPoolExecutor#beforeExecute(Thread, Runnable)} */ @Override protected void beforeExecute(final Thread thread, final Runnable runnable) { super.beforeExecute(thread, runnable); try { pauser.blockIfPaused(); } catch (final InterruptedException ie) // Curse you checked exceptions!!!! { Thread.currentThread().interrupt(); throw new RuntimeException(ie); } } /** * @see {@link ThreadPoolExecutor#execute(Runnable)} */ @Override public void execute(final Runnable command) { try { if (debug(log) && queueSemaphore.availablePermits() <= 0) debug(log, "Worker threads are saturated, scanning will block."); queueSemaphore.acquire(); } catch (final InterruptedException ie) { Thread.currentThread().interrupt(); throw new RuntimeException(ie); // Checked exceptions are the bane of my existence... } try { if (super.isTerminating() || super.isShutdown() || super.isTerminated()) { if (debug(log)) debug(log, "New work submitted during shutdown - ignoring new work."); } else { super.execute(new Runnable() { @Override public void run() { try { command.run(); } finally { // Note: queueSemaphore must be released by the worker thread, not the scanner thread! queueSemaphore.release(); } } }); } } catch (final RejectedExecutionException ree) { // If this triggers, it's a bug in the back-pressure logic queueSemaphore.release(); throw new IllegalStateException("Worker threads were saturated (available permits = " + String.valueOf(queueSemaphore.availablePermits()) + "), " + "but scanning didn't block, resulting in a RejectedExecutionException. " + "This is probably a bug in the bulk import tool - please raise an issue at https://github.com/pmonks/alfresco-bulk-import/issues/, including this full stack trace (and all \"caused by\" stack traces).", ree); } } /** * @return The current size (number of items) on the queue. */ public int getQueueSize() { return (getQueue().size()); } /** * @return The maximum possible capacity of the queue. */ public int getQueueCapacity() { return (queueCapacity); } /** * @return Is the work queue for this thread pool empty? */ public boolean isQueueEmpty() { return (getQueue().isEmpty()); } }