org.apache.pulsar.functions.windowing.EvictionPolicy Maven / Gradle / Ivy
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.pulsar.functions.windowing;
/**
* Eviction policy tracks events and decides whether
* an event should be evicted from the window or not.
*
* @param the type of event that is tracked.
* @param the type of state that is used
*/
public interface EvictionPolicy {
/**
* The action to be taken when {@link EvictionPolicy#evict(Event)} is invoked.
*/
enum Action {
/**
* expire the event and remove it from the queue.
*/
EXPIRE,
/**
* process the event in the current window of events.
*/
PROCESS,
/**
* don't include in the current window but keep the event
* in the queue for evaluating as a part of future windows.
*/
KEEP,
/**
* stop processing the queue, there cannot be anymore events
* satisfying the eviction policy.
*/
STOP
}
/**
* Decides if an event should be expired from the window, processed in the current
* window or kept for later processing.
*
* @param event the input event
* @return the {@link EvictionPolicy.Action} to be taken based on the input event
*/
Action evict(Event event);
/**
* Tracks the event to later decide whether
* {@link EvictionPolicy#evict(Event)} should evict it or not.
*
* @param event the input event to be tracked
*/
void track(Event event);
/**
* 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.
*
* @param context the eviction context
*/
void setContext(EvictionContext context);
/**
* Returns the current context that is part of this eviction policy.
*
* @return the eviction context
*/
EvictionContext getContext();
/**
* Resets the eviction policy.
*/
void reset();
/**
* Return runtime state to be checkpointed by the framework for restoring the eviction policy
* in case of failures.
*
* @return the state
*/
S getState();
/**
* Restore the eviction policy from the state that was earlier checkpointed by the framework.
*
* @param state the state
*/
void restoreState(S state);
}