org.apache.flink.streaming.api.windowing.policy

Class TimeTriggerPolicy<DATA>

java.lang.Object

org.apache.flink.streaming.api.windowing.policy.TimeTriggerPolicy<DATA>

Type Parameters:

DATA - The type of the incoming data points which are processed by this policy.

All Implemented Interfaces:

Serializable, Cloneable, ActiveTriggerPolicy<DATA>, CentralActiveTrigger<DATA>, CloneableTriggerPolicy<DATA>, TriggerPolicy<DATA>

public class TimeTriggerPolicy<DATA>
extends Object
implements ActiveTriggerPolicy<DATA>, CloneableTriggerPolicy<DATA>, CentralActiveTrigger<DATA>

This trigger policy triggers with regard to the time. The is measured using a given Timestamp implementation. A point in time is always represented as long. Therefore, parameters such as granularity and delay can be set as long value as well.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
long	granularity
protected long	startTime
TimestampWrapper<DATA>	timestampWrapper

Constructor Summary

Constructors

Constructor and Description
TimeTriggerPolicy(long granularity, TimestampWrapper<DATA> timestampWrapper) This is mostly the same as TimeTriggerPolicy(long, TimestampWrapper).

Method Summary

Modifier and Type	Method and Description
Object	activeFakeElementEmission(ActiveTriggerCallback callback) This method is only called in case the runnable triggers a window end according to the SystemTimestamp.
TimeTriggerPolicy<DATA>	clone() This method should return an exact copy of the object it belongs to including the current object state.
Runnable	createActiveTriggerRunnable(ActiveTriggerCallback callback) In case SystemTimestamp is used, a runnable is returned which triggers based on the current system time.
boolean	equals(Object other)
long	getSlideSize()
TimestampWrapper<DATA>	getTimeStampWrapper()
Object[]	notifyOnLastGlobalElement(DATA datapoint) This method is called to broadcast information about the last globally seen data point to all triggers.
boolean	notifyTrigger(DATA datapoint) Proves and returns if a new window should be started.
Object[]	preNotifyTrigger(DATA datapoint) This method checks if we missed a window end.
String	toString()

Methods inherited from class java.lang.Object

finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

startTime

protected long startTime

granularity

public long granularity

timestampWrapper

public TimestampWrapper<DATA> timestampWrapper

Constructor Detail

TimeTriggerPolicy

public TimeTriggerPolicy(long granularity,
                         TimestampWrapper<DATA> timestampWrapper)

This is mostly the same as TimeTriggerPolicy(long, TimestampWrapper). In addition to granularity and timestamp a delay can be specified for the first trigger. If the start time given by the timestamp is x, the delay is y, and the granularity is z, the first trigger will happen at x+y+z.

Parameters:

granularity - The granularity of the trigger. If this value is set to 2 the policy will trigger at every second time point

timestampWrapper - The TimestampWrapper to measure the time with. This can be either user defined of provided by the API.

Method Detail

preNotifyTrigger

public Object[] preNotifyTrigger(DATA datapoint)

This method checks if we missed a window end. If this is the case we trigger the missed windows using fake elements.

Specified by:

preNotifyTrigger in interface ActiveTriggerPolicy<DATA>

Parameters:

datapoint - the data point which arrived at the operator

Returns:

zero ore more fake data points which will be added before the the currently arrived real element gets processed.

createActiveTriggerRunnable

public Runnable createActiveTriggerRunnable(ActiveTriggerCallback callback)

In case SystemTimestamp is used, a runnable is returned which triggers based on the current system time. If any other time measure is used the method returns null.

Specified by:

createActiveTriggerRunnable in interface ActiveTriggerPolicy<DATA>

Parameters:

callback - The object which is takes the callbacks for adding fake elements out of the runnable.

Returns:

A runnable is returned which triggers based on the current system time. If any other time measure is used the method return null.

activeFakeElementEmission

public Object activeFakeElementEmission(ActiveTriggerCallback callback)

This method is only called in case the runnable triggers a window end according to the SystemTimestamp.

Parameters:

callback - The callback object.

notifyTrigger

public boolean notifyTrigger(DATA datapoint)

Description copied from interface: TriggerPolicy

Proves and returns if a new window should be started. In case the trigger occurs (return value true) the UDF will be executed on the current element buffer without the last added element which is provided as parameter. This element will be added to the buffer after the execution of the UDF. There are possibly different strategies for eviction and triggering: 1) including last data point: Better/faster for count eviction 2) excluding last data point: Essentially required for time based eviction and delta rules As 2) is required for some policies and the benefit of using 1) is small for the others, policies are implemented according to 2).

Specified by:

notifyTrigger in interface TriggerPolicy<DATA>

Parameters:

datapoint - the data point which arrived

Returns:

true if the current windows should be closed, otherwise false. In true case the given data point will be part of the next window and will not be included in the current one.

clone

public TimeTriggerPolicy<DATA> clone()

Description copied from interface: CloneableTriggerPolicy

This method should return an exact copy of the object it belongs to including the current object state.

Specified by:

clone in interface CloneableTriggerPolicy<DATA>

Overrides:

clone in class Object

Returns:

a copy of this object

equals

public boolean equals(Object other)

Overrides:

equals in class Object

getSlideSize

public long getSlideSize()

toString

public String toString()

Overrides:

toString in class Object

getTimeStampWrapper

public TimestampWrapper<DATA> getTimeStampWrapper()

notifyOnLastGlobalElement

public Object[] notifyOnLastGlobalElement(DATA datapoint)

Description copied from interface: CentralActiveTrigger

This method is called to broadcast information about the last globally seen data point to all triggers. The number of elements returned in the array will determine the number of triggers at that point, while the elements themselves are used only for active eviction.

Specified by:

notifyOnLastGlobalElement in interface CentralActiveTrigger<DATA>

Parameters:

datapoint - The last globally seen data

Returns:

An object of fake elements. If returned null or empty list, no triggers will occur.