TimeWindowView.java

/**************************************************************************************
 * Copyright (C) 2008 EsperTech, Inc. All rights reserved.                            *
 * http://esper.codehaus.org                                                          *
 * 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.view.window;

import com.espertech.esper.client.EventBean;
import com.espertech.esper.client.EventType;
import com.espertech.esper.collection.TimeWindow;
import com.espertech.esper.collection.ViewUpdatedCollection;
import com.espertech.esper.core.context.util.AgentInstanceViewFactoryChainContext;
import com.espertech.esper.core.service.EPStatementHandleCallback;
import com.espertech.esper.core.service.ExtensionServicesContext;
import com.espertech.esper.schedule.ScheduleAdjustmentCallback;
import com.espertech.esper.schedule.ScheduleHandleCallback;
import com.espertech.esper.schedule.ScheduleSlot;
import com.espertech.esper.util.StopCallback;
import com.espertech.esper.view.*;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.util.ArrayDeque;
import java.util.Iterator;

/**
 * This view is a moving timeWindow extending the specified amount of milliseconds into the past.
 * The view bases the timeWindow on the time obtained from the scheduling service.
 * All incoming events receive a timestamp and are placed in a sorted map by timestamp.
 * The view does not care about old data published by the parent view to this view.
 *
 * Events leave or expire from the time timeWindow by means of a scheduled callback registered with the
 * scheduling service. Thus child views receive updates containing old data only asynchronously
 * as the system-time-based timeWindow moves on. However child views receive updates containing new data
 * as soon as the new data arrives.
 */
public class TimeWindowView extends ViewSupport implements CloneableView, DataWindowView, ScheduleAdjustmentCallback, StoppableView, StopCallback
{
    private final TimeWindowViewFactory timeWindowViewFactory;
    private final long millisecondsBeforeExpiry;
    protected final TimeWindow timeWindow;
    private final ViewUpdatedCollection viewUpdatedCollection;
    protected final AgentInstanceViewFactoryChainContext agentInstanceContext;
    private final ScheduleSlot scheduleSlot;
    private final EPStatementHandleCallback handle;

    /**
     * Constructor.
     * @param millisecondsBeforeExpiry is the number of milliseconds before events gets pushed
     * out of the timeWindow as oldData in the update method.
     * @param viewUpdatedCollection is a collection the view must update when receiving events
     * @param timeWindowViewFactory for copying the view in a group-by
     */
    public TimeWindowView(AgentInstanceViewFactoryChainContext agentInstanceContext, TimeWindowViewFactory timeWindowViewFactory, long millisecondsBeforeExpiry, ViewUpdatedCollection viewUpdatedCollection)
    {
        this.agentInstanceContext = agentInstanceContext;
        this.timeWindowViewFactory = timeWindowViewFactory;
        this.millisecondsBeforeExpiry = millisecondsBeforeExpiry;
        this.viewUpdatedCollection = viewUpdatedCollection;
        this.scheduleSlot = agentInstanceContext.getStatementContext().getScheduleBucket().allocateSlot();
        this.timeWindow = new TimeWindow(agentInstanceContext.isRemoveStream());

        ScheduleHandleCallback callback = new ScheduleHandleCallback() {
            public void scheduledTrigger(ExtensionServicesContext extensionServicesContext)
            {
                TimeWindowView.this.expire();
            }
        };
        this.handle = new EPStatementHandleCallback(agentInstanceContext.getEpStatementAgentInstanceHandle(), callback);

        agentInstanceContext.getStatementContext().getScheduleAdjustmentService().addCallback(this);
        agentInstanceContext.getTerminationCallbacks().add(this);
    }

    public void adjust(long delta)
    {
        timeWindow.adjust(delta);
    }

    public View cloneView()
    {
        return timeWindowViewFactory.makeView(agentInstanceContext);
    }

    /**
     * Returns the size of the time window in millisecond.
     * @return size of window
     */
    public final long getMillisecondsBeforeExpiry()
    {
        return millisecondsBeforeExpiry;
    }

    /**
     * Returns the (optional) collection handling random access to window contents for prior or previous events.
     * @return buffer for events
     */
    public ViewUpdatedCollection getViewUpdatedCollection()
    {
        return viewUpdatedCollection;
    }

    public final EventType getEventType()
    {
        return parent.getEventType();
    }

    public final void update(EventBean[] newData, EventBean[] oldData)
    {
        long timestamp = agentInstanceContext.getStatementContext().getSchedulingService().getTime();

        if (oldData != null)
        {
            for (int i = 0; i < oldData.length; i++)
            {
                timeWindow.remove(oldData[i]);
            }
        }

        // we don't care about removed data from a prior view
        if ((newData != null) && (newData.length > 0))
        {
            // If we have an empty window about to be filled for the first time, schedule a callback
            // for now plus millisecondsBeforeExpiry
            if (timeWindow.isEmpty())
            {
                scheduleCallback(millisecondsBeforeExpiry);
            }

            // add data points to the timeWindow
            for (int i = 0; i < newData.length; i++)
            {
                timeWindow.add(timestamp, newData[i]);
            }

            if (viewUpdatedCollection != null)
            {
                viewUpdatedCollection.update(newData, null);
            }
        }

        // update child views
        if (this.hasViews())
        {
            updateChildren(newData, oldData);
        }
    }

    /**
     * This method removes (expires) objects from the window and schedules a new callback for the
     * time when the next oldest message would expire from the window.
     */
    protected final void expire()
    {
        long expireBeforeTimestamp = agentInstanceContext.getStatementContext().getSchedulingService().getTime() - millisecondsBeforeExpiry + 1;

        // Remove from the timeWindow any events that have an older or timestamp then the given timestamp
        // The window extends from X to (X - millisecondsBeforeExpiry + 1)
        ArrayDeque<EventBean> expired = timeWindow.expireEvents(expireBeforeTimestamp);

        // If there are child views, fireStatementStopped update method
        if (this.hasViews())
        {
            if ((expired != null) && (!expired.isEmpty()))
            {
                EventBean[] oldEvents = expired.toArray(new EventBean[expired.size()]);
                if (viewUpdatedCollection != null)
                {
                    viewUpdatedCollection.update(null, oldEvents);
                }
                updateChildren(null, oldEvents);
            }
        }

        scheduleExpiryCallback();
    }

    protected void scheduleExpiryCallback() {
        // If we still have events in the window, schedule new callback
        if (timeWindow.isEmpty())
        {
            return;
        }
        Long oldestTimestamp = timeWindow.getOldestTimestamp();
        long currentTimestamp = agentInstanceContext.getStatementContext().getSchedulingService().getTime();
        long scheduleMillisec = millisecondsBeforeExpiry - (currentTimestamp - oldestTimestamp);
        scheduleCallback(scheduleMillisec);
    }

    private void scheduleCallback(long msecAfterCurrentTime)
    {
        agentInstanceContext.getStatementContext().getSchedulingService().add(msecAfterCurrentTime, handle, scheduleSlot);
    }

    public final Iterator<EventBean> iterator()
    {
        return timeWindow.iterator();
    }

    public final String toString()
    {
        return this.getClass().getName() +
                " millisecondsBeforeExpiry=" + millisecondsBeforeExpiry;
    }

    /**
     * Returns true if the window is empty, or false if not empty.
     * @return true if empty
     */
    public boolean isEmpty()
    {
        return timeWindow.isEmpty();
    }

    public void stopView() {
        stopSchedule();
        agentInstanceContext.getTerminationCallbacks().remove(this);
    }

    public void stop() {
        stopSchedule();
    }

    public void stopSchedule() {
        if (handle != null) {
            agentInstanceContext.getStatementContext().getSchedulingService().remove(handle, scheduleSlot);
        }
        agentInstanceContext.getStatementContext().getScheduleAdjustmentService().removeCallback(this);
    }

    private static final Log log = LogFactory.getLog(TimeWindowView.class);
}