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

Class MultiTriggerPolicy<DATA>

java.lang.Object

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

Type Parameters:

DATA - the data type handled by this policy

All Implemented Interfaces:

Serializable, ActiveTriggerPolicy<DATA>, TriggerPolicy<DATA>

Direct Known Subclasses:

CloneableMultiTriggerPolicy

public class MultiTriggerPolicy<DATA>
extends Object
implements ActiveTriggerPolicy<DATA>

This class allows to use multiple trigger policies at the same time. It allows to use both, active and not active triggers.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
MultiTriggerPolicy(TriggerPolicy<DATA>... policies) This policy allows to use multiple trigger policies at the same time.

Method Summary

Modifier and Type	Method and Description
Runnable	createActiveTriggerRunnable(ActiveTriggerCallback callback) This is the factory method for a runnable.
boolean	notifyTrigger(DATA datapoint) Proves and returns if a new window should be started.
Object[]	preNotifyTrigger(DATA datapoint) Whenever an element arrives at the operator, the ActiveTriggerPolicy.preNotifyTrigger(Object) method gets called first.

Methods inherited from class java.lang.Object

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

Constructor Detail

MultiTriggerPolicy

public MultiTriggerPolicy(TriggerPolicy<DATA>... policies)

This policy allows to use multiple trigger policies at the same time. It allows to use both, active and not active triggers. This policy triggers in case at least one of the nested policies triggered. If active policies are nested all produces fake elements will be returned.

Parameters:

policies - Any active or not active trigger policies. Both types can be used at the same time.

Method Detail

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.

preNotifyTrigger

public Object[] preNotifyTrigger(DATA datapoint)

Description copied from interface: ActiveTriggerPolicy

Whenever an element arrives at the operator, the ActiveTriggerPolicy.preNotifyTrigger(Object) method gets called first. It can return zero ore more fake data points which will be added before the the currently arrived real element gets processed. This allows to handle empty windows in time based windowing with an user defined Timestamp. Triggers are not called on fake datapoints. A fake datapoint is always considered as triggered.

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)

Description copied from interface: ActiveTriggerPolicy

This is the factory method for a runnable. This factory method gets called at the start up of the operator. The returned runnable will be executed in its own thread and can submit fake elements at any time through an ActiveTriggerCallback. This allows to have time based triggers based on any system internal time measure. Triggers are not called on fake datapoints. A fake datapoint is always considered as triggered.

Specified by:

createActiveTriggerRunnable in interface ActiveTriggerPolicy<DATA>

Parameters:

callback - A callback object which allows to add fake elements from within the returned Runnable.

Returns:

The runnable implementation or null in case there is no. In case an ActiveTriggerPolicy is used, it can implement own Runnable classes. Such Runnable classes will be executed as an own thread and can submit fake elements, to the element buffer at any time.