/*
* Copyright 2004 Sun Microsystems, Inc.
*
* Licensed 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.roller.util;
import java.util.HashMap;
import java.util.Map;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.roller.util.cache.Cache;
import org.apache.roller.util.cache.CacheManager;
import org.apache.roller.util.cache.ExpiringCacheEntry;
/**
* A tool used to provide throttling support.
*
* The basic idea is that if the # of hits from a client within a certain
* interval of time is greater than the threshold value then the client is
* considered to be abusive.
*/
public class GenericThrottle {
private static Log log = LogFactory.getLog(GenericThrottle.class);
// threshold and interval to determine who is abusive
private int threshold = 1;
private int interval = 0;
// a cache to maintain the data
Cache clientHistoryCache = null;
public GenericThrottle(int thresh, int inter, int maxEntries) {
// threshold can't be negative, that would mean everyone is abusive
if(thresh > -1) {
this.threshold = thresh;
}
// interval must be a positive value
if(inter > 0) {
this.interval = inter;
}
// max entries must be a positive value
if(maxEntries < 0) {
maxEntries = 1;
}
// cache props
Map cacheProps = new HashMap();
cacheProps.put("id", "throttle");
cacheProps.put("size", ""+maxEntries);
cacheProps.put("timeout", ""+this.interval);
// get cache instance. handler is null cuz we don't want to register it
this.clientHistoryCache = CacheManager.constructCache(null, cacheProps);
}
/**
* Process a new hit from the client.
*
* Each call to this method increments the hit count for the client and
* then returns a boolean value indicating if the hit has pushed the client
* over the threshold.
*
* @retuns true if client is abusive, false otherwise
*/
public boolean processHit(String clientId) {
if(clientId == null) {
return false;
}
// see if we have any info about this client yet
ClientInfo client = null;
ExpiringCacheEntry cacheEntry = (ExpiringCacheEntry) this.clientHistoryCache.get(clientId);
if(cacheEntry != null) {
log.debug("HIT "+clientId);
client = (ClientInfo) cacheEntry.getValue();
// this means entry had expired
if(client == null) {
log.debug("EXPIRED "+clientId);
this.clientHistoryCache.remove(clientId);
}
}
// if we already know this client then update their hit count and
// see if they have surpassed the threshold
if(client != null) {
client.hits++;
log.debug("STATUS "+clientId+" - "+client.hits+" hits since "+client.start);
// abusive client
if(client.hits > this.threshold) {
return true;
}
} else {
log.debug("NEW "+clientId);
// first timer
ClientInfo newClient = new ClientInfo();
newClient.hits = 1;
newClient.id = clientId;
ExpiringCacheEntry newEntry = new ExpiringCacheEntry(newClient, this.interval);
this.clientHistoryCache.put(clientId, newEntry);
}
return false;
}
/**
* Check the current status of a client.
*
* A client is considered abusive if the number of hits from the client
* within the configured interval is greater than the set threshold.
*
* @returns true if client is abusive, false otherwise.
*/
public boolean isAbusive(String clientId) {
if(clientId == null) {
return false;
}
// see if we have any info about this client
ClientInfo client = null;
ExpiringCacheEntry cacheEntry = (ExpiringCacheEntry) this.clientHistoryCache.get(clientId);
if(cacheEntry != null) {
log.debug("HIT "+clientId);
client = (ClientInfo) cacheEntry.getValue();
// this means entry had expired
if(client == null) {
log.debug("EXPIRED "+clientId);
this.clientHistoryCache.remove(clientId);
}
}
if(client != null) {
return (client.hits > this.threshold);
} else {
return false;
}
}
// just something to keep a few properties in
private class ClientInfo {
public String id = null;
public int hits = 0;
public java.util.Date start = new java.util.Date();
}
}