com.espertech.esper.runtime.internal.kernel.updatedispatch.UpdateDispatchFutureSpin Maven / Gradle / Ivy

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/*
 ***************************************************************************************
 *  Copyright (C) 2006 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.runtime.internal.kernel.updatedispatch;

import com.espertech.esper.common.internal.schedule.TimeSourceService;
import com.espertech.esper.common.internal.statement.dispatch.Dispatchable;
import com.espertech.esper.common.internal.statement.dispatch.UpdateDispatchView;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * UpdateDispatchFutureSpin can be added to a dispatch queue that is thread-local. It represents
 * is a stand-in for a future dispatching of a statement result to statement listeners.
 * 
 * UpdateDispatchFutureSpin is aware of future and past dispatches:
 * (newest) DF3   <-->   DF2  <-->  DF1  (oldest), and uses a spin lock to block if required
 */
public class UpdateDispatchFutureSpin implements Dispatchable {
    private static final Logger log = LoggerFactory.getLogger(UpdateDispatchFutureSpin.class);
    private UpdateDispatchViewBlockingSpin view;
    private UpdateDispatchFutureSpin earlier;
    private volatile boolean isCompleted;
    private long msecTimeout;
    private TimeSourceService timeSourceService;

    /**
     * Ctor.
     *
     * @param view              is the blocking dispatch view through which to execute a dispatch
     * @param earlier           is the older future
     * @param msecTimeout       is the timeout period to wait for listeners to complete a prior dispatch
     * @param timeSourceService time source provider
     */
    public UpdateDispatchFutureSpin(UpdateDispatchViewBlockingSpin view, UpdateDispatchFutureSpin earlier, long msecTimeout, TimeSourceService timeSourceService) {
        this.view = view;
        this.earlier = earlier;
        this.msecTimeout = msecTimeout;
        this.timeSourceService = timeSourceService;
    }

    /**
     * Ctor - use for the first future to indicate completion.
     *
     * @param timeSourceService time source provider
     */
    public UpdateDispatchFutureSpin(TimeSourceService timeSourceService) {
        isCompleted = true;
        this.timeSourceService = timeSourceService;
    }

    /**
     * Returns true if the dispatch completed for this future.
     *
     * @return true for completed, false if not
     */
    public boolean isCompleted() {
        return isCompleted;
    }

    public void execute() {
        if (!earlier.isCompleted) {
            long spinStartTime = timeSourceService.getTimeMillis();

            while (!earlier.isCompleted) {
                Thread.yield();

                long spinDelta = timeSourceService.getTimeMillis() - spinStartTime;
                if (spinDelta > msecTimeout) {
                    log.info("Spin wait timeout exceeded in listener dispatch for statement '" + view.getStatementResultService().getStatementName() + "'");
                    break;
                }
            }
        }

        view.execute();

        completed();
    }

    public UpdateDispatchView getView() {
        return view;
    }

    public void cancelled() {
        completed();
    }

    private void completed() {
        isCompleted = true;
        earlier = null;
    }
}