Package org.pipecraft.infra.monitoring.sliding

Class SlidingWindow<E,R,Q>

java.lang.Object

org.pipecraft.infra.monitoring.sliding.SlidingWindow<E,R,Q>

Type Parameters:

E - The type of an event to be reported

R - The type of the record stored per time slot. Must be thread safe

Q - The type of query results

Direct Known Subclasses:

AverageSlidingWindow, EventRateSlidingWindow

public abstract class SlidingWindow<E,R,Q>
extends Object

An abstract sliding window. A sliding window object is notified with events as they occur, and supports querying the recently collected data. The data aggregation and the query semantics are implementation dependent.

Author:

Eyal Schneider

Constructor Summary

Constructors

Constructor	Description
SlidingWindow(int slotsCount, int slotTime, TimeUnit slotTimeUnit, ScheduledExecutorService ex)	Constructor

Method Summary

Modifier and Type	Method	Description
protected abstract void	clearRecord(R record)	clears a given record by resetting its data.
protected R	getRecord(int pos)
int	getSlotsCount()
int	getSlotTime()
TimeUnit	getSlotTimeUnit()
long	getWindowTimeSpanMs()
void	newEvent(E event)	Reports a new event
protected abstract void	newEvent(E event, R rec)	Reports a new event to be appended into a given time slot record
protected abstract R	newRecord()
protected abstract R[]	newRecordArray(int size)
Q	query()
Q	query(int lookback)
protected abstract Q	query(R[] records)
void	shutdown()	Terminates the sliding window.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SlidingWindow

public SlidingWindow(int slotsCount,
                     int slotTime,
                     TimeUnit slotTimeUnit,
                     ScheduledExecutorService ex)

Constructor

Parameters:

slotsCount - The number of time slots in the sliding window

slotTime - The time duration represented by one slot

slotTimeUnit - The time unit of slotTime

ex - The executor to run the time-pulse task on.

Method Detail

newEvent

public void newEvent(E event)

Reports a new event

Parameters:

event - The event

newEvent

protected abstract void newEvent(E event,
                                 R rec)

Reports a new event to be appended into a given time slot record

Parameters:

event - The event

rec - The record to be updated

newRecord

protected abstract R newRecord()

Returns:

A new, empty record. Called only during the construction of the sliding window.

newRecordArray

protected abstract R[] newRecordArray(int size)

Parameters:

size - The required size

Returns:

A new, empty record array of the given size.

clearRecord

protected abstract void clearRecord(R record)

clears a given record by resetting its data. It is up to the implementation to decide how to deal with data consistency in case of a concurrent query that inspects that record. It is highly unlikely that an event is registered in the record during this operation.

query

public Q query()

Returns:

The query result, relevant for the complete time period covered by the sliding window.

query

public Q query(int lookback)

Parameters:

lookback - The number of time slots to look back on (must be between 1 and the number of slots defined in the constructor)

Returns:

The query result, relevant for the time period covered by the given lookback.

query

protected abstract Q query(R[] records)

Parameters:

records - the array of records to inspect. Ordered from oldest to newest.

Returns:

The query result, relevant for the time period covered by the given lookback.

shutdown

public void shutdown()

Terminates the sliding window. Note: subsequent queries may return undefined results!

getSlotTime

public int getSlotTime()

Returns:

The time duration represented by a single slot

getSlotTimeUnit

public TimeUnit getSlotTimeUnit()

Returns:

The time unit by which getSlotTime() is measured

getWindowTimeSpanMs

public long getWindowTimeSpanMs()

Returns:

The total time covered by this sliding window, in milliseconds

getSlotsCount

public int getSlotsCount()

Returns:

The number of slots in this sliding window

getRecord

protected R getRecord(int pos)

Parameters:

pos - A position in the cyclic array

Returns:

The record in the given position