Java tutorial
/************************************************************************************** * Copyright (C) 2006-2015 EsperTech Inc. All rights reserved. * * http://www.espertech.com/esper * * http://www.espertech.com * * ---------------------------------------------------------------------------------- * * The software in this package is published under the terms of the GPL license * * a copy of which has been included with this distribution in the license.txt file. * **************************************************************************************/ package com.espertech.esper.epl.named; import com.espertech.esper.core.context.util.EPStatementAgentInstanceHandle; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import java.util.List; import java.util.Map; /** * A spin-locking implementation of a latch for use in guaranteeing delivery between * a delta stream produced by a named window and consumable by another statement. */ public class NamedWindowConsumerLatchSpin extends NamedWindowConsumerLatch { private static final Log log = LogFactory.getLog(NamedWindowConsumerLatchSpin.class); // The earlier latch is the latch generated before this latch private NamedWindowConsumerLatchFactory factory; private NamedWindowConsumerLatchSpin earlier; private Thread currentThread; private volatile boolean isCompleted; /** * Ctor. * @param earlier the latch before this latch that this latch should be waiting for */ public NamedWindowConsumerLatchSpin(NamedWindowDeltaData deltaData, Map<EPStatementAgentInstanceHandle, List<NamedWindowConsumerView>> dispatchTo, NamedWindowConsumerLatchFactory factory, NamedWindowConsumerLatchSpin earlier) { super(deltaData, dispatchTo); this.factory = factory; this.earlier = earlier; } /** * Ctor - use for the first and unused latch to indicate completion. */ public NamedWindowConsumerLatchSpin(NamedWindowConsumerLatchFactory factory) { super(null, null); this.factory = factory; isCompleted = true; earlier = null; } /** * Returns true if the dispatch completed for this future. * @return true for completed, false if not */ public boolean isCompleted() { return isCompleted; } /** * Blocking call that returns only when the earlier latch completed. * @return unit of the latch */ public void await() { if (earlier.isCompleted) { currentThread = Thread.currentThread(); return; } if (earlier.getCurrentThread() == Thread.currentThread()) { currentThread = Thread.currentThread(); return; } long spinStartTime = factory.getTimeSourceService().getTimeMillis(); while (!earlier.isCompleted) { Thread.yield(); long spinDelta = factory.getTimeSourceService().getTimeMillis() - spinStartTime; if (spinDelta > factory.getMsecWait()) { log.info("Spin wait timeout exceeded in named window '" + factory.getName() + "' consumer dispatch at " + factory.getMsecWait() + "ms for " + factory.getName() + ", consider disabling named window consumer dispatch latching for better performance"); break; } } } public Thread getCurrentThread() { return currentThread; } /** * Called to indicate that the latch completed and a later latch can start. */ public void done() { isCompleted = true; earlier = null; } }