Package org.apache.storm.windowing

Interface EvictionPolicy<T,S>

Type Parameters:

T - the type of event that is tracked.

All Known Implementing Classes:

CountEvictionPolicy, TimeEvictionPolicy, WatermarkCountEvictionPolicy, WatermarkTimeEvictionPolicy

public interface EvictionPolicy<T,S>

Eviction policy tracks events and decides whether an event should be evicted from the window or not.

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static enum	EvictionPolicy.Action	The action to be taken when evict(Event) is invoked.

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.
S	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(S 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.
void	track(Event<T> event)	Tracks the event to later decide whether evict(Event) should evict it or not.

Method Details

evict

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.

Parameters:

event - the input event

Returns:

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

track

void track(Event<T> event)

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

Parameters:

event - the input event to be tracked

getContext

EvictionContext getContext()

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

Returns:

the eviction context

setContext

void setContext(EvictionContext context)

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.

Parameters:

context - the eviction context

reset

void reset()

Resets the eviction policy.

getState

S getState()

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

Returns:

the state

restoreState

void restoreState(S state)

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

Parameters:

state - the state