| /** |
| * 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.storm.windowing; |
| |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * Eviction policy that evicts events based on time duration. |
| */ |
| public class TimeEvictionPolicy<T> implements EvictionPolicy<T, EvictionContext> { |
| private static final Logger LOG = LoggerFactory.getLogger(TimeEvictionPolicy.class); |
| |
| private final int windowLength; |
| protected volatile EvictionContext evictionContext; |
| private long delta; |
| |
| /** |
| * 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 = evictionContext == null ? System.currentTimeMillis() : evictionContext.getReferenceTime(); |
| long diff = now - event.getTimestamp(); |
| if (diff >= (windowLength + delta)) { |
| return Action.EXPIRE; |
| } else if (diff < 0) { // do not process events beyond current ts |
| return Action.KEEP; |
| } |
| return Action.PROCESS; |
| } |
| |
| @Override |
| public void track(Event<T> event) { |
| // NOOP |
| } |
| |
| @Override |
| public EvictionContext getContext() { |
| return evictionContext; |
| } |
| |
| @Override |
| public void setContext(EvictionContext context) { |
| EvictionContext prevContext = evictionContext; |
| evictionContext = context; |
| // compute window length adjustment (delta) to account for time drift |
| if (context.getSlidingInterval() != null) { |
| if (prevContext == null) { |
| delta = Integer.MAX_VALUE; // consider all events for the initial window |
| } else { |
| delta = context.getReferenceTime() - prevContext.getReferenceTime() - context.getSlidingInterval(); |
| if (Math.abs(delta) > 100) { |
| LOG.warn("Possible clock drift or long running computation in window; " |
| + "Previous eviction time: {}, current eviction time: {}", |
| prevContext.getReferenceTime(), |
| context.getReferenceTime()); |
| } |
| } |
| } |
| } |
| |
| @Override |
| public void reset() { |
| // NOOP |
| } |
| |
| @Override |
| public EvictionContext getState() { |
| return evictionContext; |
| } |
| |
| @Override |
| public void restoreState(EvictionContext state) { |
| this.evictionContext = state; |
| } |
| |
| @Override |
| public String toString() { |
| return "TimeEvictionPolicy{" |
| + "windowLength=" + windowLength |
| + ", evictionContext=" + evictionContext |
| + '}'; |
| } |
| } |