| /** |
| * 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; |
| |
| /** |
| * An eviction policy that evicts events based on time duration taking watermark time and event lag into account. |
| */ |
| public class WatermarkTimeEvictionPolicy<T> extends TimeEvictionPolicy<T> { |
| private final int lag; |
| |
| /** |
| * Constructs a WatermarkTimeEvictionPolicy that evicts events older than the given window length in millis. |
| * |
| * @param windowLength the window length in milliseconds |
| */ |
| public WatermarkTimeEvictionPolicy(int windowLength) { |
| this(windowLength, Integer.MAX_VALUE); |
| } |
| |
| /** |
| * Constructs a WatermarkTimeEvictionPolicy that evicts events older than the given window length in millis. The lag parameter can be |
| * used in the case of event based ts to break the queue scan early. |
| * |
| * @param windowLength the window length in milliseconds |
| * @param lag the max event lag in milliseconds |
| */ |
| public WatermarkTimeEvictionPolicy(int windowLength, int lag) { |
| super(windowLength); |
| this.lag = lag; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * <p/> |
| * Keeps events with future ts in the queue for processing in the next window. If the ts difference is more than the lag, stops scanning |
| * the queue for the current window. |
| */ |
| @Override |
| public Action evict(Event<T> event) { |
| if (evictionContext == null) { |
| //It is possible to get asked about eviction before we have a context, due to WindowManager.compactWindow. |
| //In this case we should hold on to all the events. When the first watermark is received, the context will be set, |
| //and the events will be reevaluated for eviction |
| return Action.STOP; |
| } |
| |
| long referenceTime = evictionContext.getReferenceTime(); |
| long diff = referenceTime - event.getTimestamp(); |
| if (diff < -lag) { |
| return Action.STOP; |
| } else if (diff < 0) { |
| return Action.KEEP; |
| } else { |
| return super.evict(event); |
| } |
| } |
| |
| @Override |
| public String toString() { |
| return "WatermarkTimeEvictionPolicy{" |
| + "lag=" + lag |
| + "} " |
| + super.toString(); |
| } |
| |
| } |