EvictionPolicy (Storm 2.7.1 API)

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 class EvictionPolicy.Action
The action to be taken when evict(Event) is invoked.

Method Summary

All Methods Instance Methods Abstract Methods
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 Detail
  - 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