/**
* 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 backtype.storm.windowing;
/**
* Eviction policy that evicts events based on time duration.
*/
public class TimeEvictionPolicy<T> implements EvictionPolicy<T> {
private final int windowLength;
/**
* The reference time in millis for window calculations and
* expiring events. If not set it will default to System.currentTimeMillis()
*/
protected Long referenceTime;
/**
* Constructs a TimeEvictionPolicy that evicts events older
* than the given window length in millis
*
* @param windowLength the duration in milliseconds
*/
public TimeEvictionPolicy(int windowLength) {
this.windowLength = windowLength;
}
/**
* {@inheritDoc}
*/
@Override
public Action evict(Event<T> event) {
long now = referenceTime == null ? System.currentTimeMillis() : referenceTime;
long diff = now - event.getTimestamp();
if (diff >= windowLength) {
return Action.EXPIRE;
}
return Action.PROCESS;
}
@Override
public void track(Event<T> event) {
// NOOP
}
@Override
public void setContext(Object context) {
referenceTime = ((Number) context).longValue();
}
@Override
public String toString() {
return "TimeEvictionPolicy{" +
"windowLength=" + windowLength +
", referenceTime=" + referenceTime +
'}';
}
}