001/** 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018package org.apache.hadoop.util; 019 020/** 021 * CacheableIPList loads a list of subnets from a file. 022 * The list is cached and the cache can be refreshed by specifying cache timeout. 023 * A negative value of cache timeout disables any caching. 024 * 025 * Thread safe. 026 */ 027 028public class CacheableIPList implements IPList { 029 private final long cacheTimeout; 030 private volatile long cacheExpiryTimeStamp; 031 private volatile FileBasedIPList ipList; 032 033 public CacheableIPList(FileBasedIPList ipList, long cacheTimeout) { 034 this.cacheTimeout = cacheTimeout; 035 this.ipList = ipList; 036 updateCacheExpiryTime(); 037 } 038 039 /** 040 * Reloads the ip list 041 */ 042 private void reset() { 043 ipList = ipList.reload(); 044 updateCacheExpiryTime(); 045 } 046 047 private void updateCacheExpiryTime() { 048 if (cacheTimeout < 0) { 049 cacheExpiryTimeStamp = -1; // no automatic cache expiry. 050 }else { 051 cacheExpiryTimeStamp = System.currentTimeMillis() + cacheTimeout; 052 } 053 } 054 055 /** 056 * Refreshes the ip list 057 */ 058 public void refresh () { 059 cacheExpiryTimeStamp = 0; 060 } 061 062 @Override 063 public boolean isIn(String ipAddress) { 064 //is cache expired 065 //Uses Double Checked Locking using volatile 066 if (cacheExpiryTimeStamp >= 0 && cacheExpiryTimeStamp < System.currentTimeMillis()) { 067 synchronized(this) { 068 //check if cache expired again 069 if (cacheExpiryTimeStamp < System.currentTimeMillis()) { 070 reset(); 071 } 072 } 073 } 074 return ipList.isIn(ipAddress); 075 } 076}