/**************************************************************************************
* 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.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.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;
/**
* A data view that aggregates events in a stream and releases them in one batch at every specified time interval.
* The view works similar to a time_window but in not continuous.
* The view releases the batched events after the interval as new data to child views. The prior batch if
* not empty is released as old data to child view. The view doesn't release intervals with no old or new data.
* It also does not collect old data published by a parent view.
*
* For example, we want to calculate the average of IBM stock every hour, for the last hour.
* The view accepts 2 parameter combinations.
* (1) A time interval is supplied with a reference point - based on this point the intervals are set.
* (1) A time interval is supplied but no reference point - the reference point is set when the first event arrives.
*
* If there are no events in the current and prior batch, the view will not invoke the update method of child views.
* In that case also, no next callback is scheduled with the scheduling service until the next event arrives.
*/
public class TimeBatchView extends ViewSupport implements CloneableView, StoppableView, StopCallback, DataWindowView {
// View parameters
private final TimeBatchViewFactory timeBatchViewFactory;
protected final AgentInstanceViewFactoryChainContext agentInstanceContext;
protected final long msecIntervalSize;
protected final Long initialReferencePoint;
protected final boolean isForceOutput;
protected final boolean isStartEager;
protected final ViewUpdatedCollection viewUpdatedCollection;
protected final ScheduleSlot scheduleSlot;
protected EPStatementHandleCallback handle;
// Current running parameters
protected Long currentReferencePoint;
protected ArrayDeque<EventBean> lastBatch = null;
protected ArrayDeque<EventBean> currentBatch = new ArrayDeque<EventBean>();
protected boolean isCallbackScheduled;
/**
* Constructor.
* @param msecIntervalSize is the number of milliseconds to batch events for
* @param referencePoint is the reference point onto which to base intervals, or null if
* there is no such reference point supplied
* @param viewUpdatedCollection is a collection that the view must update when receiving events
* @param timeBatchViewFactory for copying this view in a group-by
* @param forceOutput is true if the batch should produce empty output if there is no value to output following time intervals
* @param isStartEager is true for start-eager
*/
public TimeBatchView(TimeBatchViewFactory timeBatchViewFactory,
AgentInstanceViewFactoryChainContext agentInstanceContext,
long msecIntervalSize,
Long referencePoint,
boolean forceOutput,
boolean isStartEager,
ViewUpdatedCollection viewUpdatedCollection)
{
this.agentInstanceContext = agentInstanceContext;
this.timeBatchViewFactory = timeBatchViewFactory;
this.msecIntervalSize = msecIntervalSize;
this.initialReferencePoint = referencePoint;
this.isStartEager = isStartEager;
this.viewUpdatedCollection = viewUpdatedCollection;
this.isForceOutput = forceOutput;
this.scheduleSlot = agentInstanceContext.getStatementContext().getScheduleBucket().allocateSlot();
// schedule the first callback
if (isStartEager)
{
if (currentReferencePoint == null)
{
currentReferencePoint = agentInstanceContext.getStatementContext().getSchedulingService().getTime();
}
scheduleCallback();
isCallbackScheduled = true;
}
agentInstanceContext.addTerminationCallback(this);
}
public View cloneView()
{
return timeBatchViewFactory.makeView(agentInstanceContext);
}
/**
* Returns the interval size in milliseconds.
* @return batch size
*/
public final long getMsecIntervalSize()
{
return msecIntervalSize;
}
/**
* Gets the reference point to use to anchor interval start and end dates to.
* @return is the millisecond reference point.
*/
public final Long getInitialReferencePoint()
{
return initialReferencePoint;
}
/**
* True for force-output.
* @return indicates force-output
*/
public boolean isForceOutput()
{
return isForceOutput;
}
/**
* True for start-eager.
* @return indicates start-eager
*/
public boolean isStartEager()
{
return isStartEager;
}
public final EventType getEventType()
{
return parent.getEventType();
}
public void update(EventBean[] newData, EventBean[] oldData)
{
// we don't care about removed data from a prior view
if ((newData == null) || (newData.length == 0))
{
return;
}
// If we have an empty window about to be filled for the first time, schedule a callback
if (currentBatch.isEmpty())
{
if (currentReferencePoint == null)
{
currentReferencePoint = initialReferencePoint;
if (currentReferencePoint == null)
{
currentReferencePoint = agentInstanceContext.getStatementContext().getSchedulingService().getTime();
}
}
// Schedule the next callback if there is none currently scheduled
if (!isCallbackScheduled)
{
scheduleCallback();
isCallbackScheduled = true;
}
}
// add data points to the timeWindow
for (EventBean newEvent : newData) {
currentBatch.add(newEvent);
}
// We do not update child views, since we batch the events.
}
/**
* This method updates child views and clears the batch of events.
* We schedule a new callback at this time if there were events in the batch.
*/
protected void sendBatch()
{
isCallbackScheduled = false;
// If there are child views and the batch was filled, fireStatementStopped update method
if (this.hasViews())
{
// Convert to object arrays
EventBean[] newData = null;
EventBean[] oldData = null;
if (!currentBatch.isEmpty())
{
newData = currentBatch.toArray(new EventBean[currentBatch.size()]);
}
if ((lastBatch != null) && (!lastBatch.isEmpty()))
{
oldData = lastBatch.toArray(new EventBean[lastBatch.size()]);
}
// Post new data (current batch) and old data (prior batch)
if (viewUpdatedCollection != null)
{
viewUpdatedCollection.update(newData, oldData);
}
if ((newData != null) || (oldData != null) || (isForceOutput))
{
updateChildren(newData, oldData);
}
}
// Only if forceOutput is enabled or
// there have been any events in this or the last interval do we schedule a callback,
// such as to not waste resources when no events arrive.
if ((!currentBatch.isEmpty()) || ((lastBatch != null) && (!lastBatch.isEmpty()))
||
(isForceOutput))
{
scheduleCallback();
isCallbackScheduled = true;
}
lastBatch = currentBatch;
currentBatch = new ArrayDeque<EventBean>();
}
/**
* Returns true if the window is empty, or false if not empty.
* @return true if empty
*/
public boolean isEmpty()
{
if (lastBatch != null)
{
if (!lastBatch.isEmpty())
{
return false;
}
}
return currentBatch.isEmpty();
}
public final Iterator<EventBean> iterator()
{
return currentBatch.iterator();
}
public final String toString()
{
return this.getClass().getName() +
" msecIntervalSize=" + msecIntervalSize +
" initialReferencePoint=" + initialReferencePoint;
}
protected void scheduleCallback()
{
long current = agentInstanceContext.getStatementContext().getSchedulingService().getTime();
long afterMSec = computeWaitMSec(current, this.currentReferencePoint, this.msecIntervalSize);
ScheduleHandleCallback callback = new ScheduleHandleCallback() {
public void scheduledTrigger(ExtensionServicesContext extensionServicesContext)
{
TimeBatchView.this.sendBatch();
}
};
handle = new EPStatementHandleCallback(agentInstanceContext.getEpStatementAgentInstanceHandle(), callback);
agentInstanceContext.getStatementContext().getSchedulingService().add(afterMSec, handle, scheduleSlot);
}
/**
* Given a current time and a reference time and an interval size, compute the amount of
* milliseconds till the next interval.
* @param current is the current time
* @param reference is the reference point
* @param interval is the interval size
* @return milliseconds after current time that marks the end of the current interval
*/
protected static long computeWaitMSec(long current, long reference, long interval)
{
// Example: current c=2300, reference r=1000, interval i=500, solution s=200
//
// int n = ((2300 - 1000) / 500) = 2
// r + (n + 1) * i - c = 200
//
// Negative example: current c=2300, reference r=4200, interval i=500, solution s=400
// int n = ((2300 - 4200) / 500) = -3
// r + (n + 1) * i - c = 4200 - 3*500 - 2300 = 400
//
long n = (current - reference) / interval;
if (reference > current) // References in the future need to deduct one window
{
n--;
}
long solution = reference + (n + 1) * interval - current;
if (solution == 0)
{
return interval;
}
return solution;
}
public void stopView() {
stopSchedule();
agentInstanceContext.removeTerminationCallback(this);
}
public void stop() {
stopSchedule();
}
public void stopSchedule() {
if (handle != null) {
agentInstanceContext.getStatementContext().getSchedulingService().remove(handle, scheduleSlot);
}
}
private static final Log log = LogFactory.getLog(TimeBatchView.class);
}