Package org.apache.storm.windowing

Class TimeEvictionPolicy<T>

java.lang.Object

org.apache.storm.windowing.TimeEvictionPolicy<T>

All Implemented Interfaces:

EvictionPolicy<T,EvictionContext>

Direct Known Subclasses:

WatermarkTimeEvictionPolicy

public class TimeEvictionPolicy<T>
extends Object
implements EvictionPolicy<T,EvictionContext>

Eviction policy that evicts events based on time duration.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.storm.windowing.EvictionPolicy

EvictionPolicy.Action

Field Summary

Fields

Modifier and Type	Field	Description
protected EvictionContext	evictionContext

Constructor Summary

Constructors

Constructor	Description
TimeEvictionPolicy(int windowLength)	Constructs a TimeEvictionPolicy that evicts events older than the given window length in millis.

Method Summary

Modifier and Type	Method	Description
EvictionPolicy.Action	evict(Event<T> event)	Decides if an event should be expired from the window, processed in the current window or kept for later processing.
EvictionContext	getContext()	Returns the current context that is part of this eviction policy.
EvictionContext	getState()	Return runtime state to be checkpointed by the framework for restoring the eviction policy in case of failures.
void	reset()	Resets the eviction policy.
void	restoreState(EvictionContext state)	Restore the eviction policy from the state that was earlier checkpointed by the framework.
void	setContext(EvictionContext context)	Sets a context in the eviction policy that can be used while evicting the events.
String	toString()
void	track(Event<T> event)	Tracks the event to later decide whether EvictionPolicy.evict(Event) should evict it or not.

Methods inherited from class java.lang.Object

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

Field Details

evictionContext

protected volatile EvictionContext evictionContext

Constructor Details

TimeEvictionPolicy

public TimeEvictionPolicy(int windowLength)

Constructs a TimeEvictionPolicy that evicts events older than the given window length in millis.

Parameters:

windowLength - the duration in milliseconds

Method Details

evict

public EvictionPolicy.Action evict(Event<T> event)

Decides if an event should be expired from the window, processed in the current window or kept for later processing.

Specified by:

evict in interface EvictionPolicy<T,EvictionContext>

Parameters:

event - the input event

Returns:

the EvictionPolicy.Action to be taken based on the input event

track

public void track(Event<T> event)

Description copied from interface: EvictionPolicy

Tracks the event to later decide whether EvictionPolicy.evict(Event) should evict it or not.

Specified by:

track in interface EvictionPolicy<T,EvictionContext>

Parameters:

event - the input event to be tracked

getContext

public EvictionContext getContext()

Description copied from interface: EvictionPolicy

Returns the current context that is part of this eviction policy.

Specified by:

getContext in interface EvictionPolicy<T,EvictionContext>

Returns:

the eviction context

setContext

public void setContext(EvictionContext context)

Description copied from interface: EvictionPolicy

Sets a context in the eviction policy that can be used while evicting the events. E.g. For TimeEvictionPolicy, this could be used to set the reference timestamp.

Specified by:

setContext in interface EvictionPolicy<T,EvictionContext>

Parameters:

context - the eviction context

reset

public void reset()

Description copied from interface: EvictionPolicy

Resets the eviction policy.

Specified by:

reset in interface EvictionPolicy<T,EvictionContext>

getState

public EvictionContext getState()

Description copied from interface: EvictionPolicy

Return runtime state to be checkpointed by the framework for restoring the eviction policy in case of failures.

Specified by:

getState in interface EvictionPolicy<T,EvictionContext>

Returns:

the state

restoreState

public void restoreState(EvictionContext state)

Description copied from interface: EvictionPolicy

Restore the eviction policy from the state that was earlier checkpointed by the framework.

Specified by:

restoreState in interface EvictionPolicy<T,EvictionContext>

Parameters:

state - the state

toString

public String toString()

Overrides:

toString in class Object