| /** |
| * 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.hadoop.util; |
| |
| /** |
| * CacheableIPList loads a list of subnets from a file. |
| * The list is cached and the cache can be refreshed by specifying cache timeout. |
| * A negative value of cache timeout disables any caching. |
| * |
| * Thread safe. |
| */ |
| |
| public class CacheableIPList implements IPList { |
| private final long cacheTimeout; |
| private volatile long cacheExpiryTimeStamp; |
| private volatile FileBasedIPList ipList; |
| |
| public CacheableIPList(FileBasedIPList ipList, long cacheTimeout) { |
| this.cacheTimeout = cacheTimeout; |
| this.ipList = ipList; |
| updateCacheExpiryTime(); |
| } |
| |
| /** |
| * Reloads the ip list |
| */ |
| private void reset() { |
| ipList = ipList.reload(); |
| updateCacheExpiryTime(); |
| } |
| |
| private void updateCacheExpiryTime() { |
| if (cacheTimeout < 0) { |
| cacheExpiryTimeStamp = -1; // no automatic cache expiry. |
| }else { |
| cacheExpiryTimeStamp = System.currentTimeMillis() + cacheTimeout; |
| } |
| } |
| |
| /** |
| * Refreshes the ip list |
| */ |
| public void refresh () { |
| cacheExpiryTimeStamp = 0; |
| } |
| |
| @Override |
| public boolean isIn(String ipAddress) { |
| //is cache expired |
| //Uses Double Checked Locking using volatile |
| if (cacheExpiryTimeStamp >= 0 && cacheExpiryTimeStamp < System.currentTimeMillis()) { |
| synchronized(this) { |
| //check if cache expired again |
| if (cacheExpiryTimeStamp < System.currentTimeMillis()) { |
| reset(); |
| } |
| } |
| } |
| return ipList.isIn(ipAddress); |
| } |
| } |