isapir commented on code in PR #607: URL: https://github.com/apache/tomcat/pull/607#discussion_r1154792436
########## java/org/apache/catalina/util/TimeBucketCounter.java: ########## @@ -0,0 +1,217 @@ +/* + * 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.catalina.util; + +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.atomic.AtomicInteger; + +/** + * this class maintains a thread safe hash map that has timestamp-based buckets + * followed by a string for a key, and a counter for a value. each time the + * increment() method is called it adds the key if it does not exist, increments + * its value and returns it. + * + * a maintenance thread cleans up keys that are prefixed by previous timestamp + * buckets. + */ +public class TimeBucketCounter { + + /** + * Map to hold the buckets + */ + private final ConcurrentHashMap<String, AtomicInteger> map = new ConcurrentHashMap<>(); + + /** + * Milliseconds bucket size as a Power of 2 for bit shift math, e.g. + * 16 for 65_536ms which is about 1:05 minute + */ + private final int numBits; + + /** + * ratio of actual duration to config duration + */ + private final double ratio; + + /** + * flag for the maintenance thread + */ + volatile boolean isRunning = false; + + /** + * + * @param bucketDuration duration in seconds, e.g. for 1 minute pass 60 + */ + public TimeBucketCounter(int bucketDuration) { + + int durationMillis = bucketDuration * 1000; + + int bits = 0; + int pof2 = nextPowerOf2(durationMillis); + int bitCheck = pof2; + while (bitCheck > 1) { + bitCheck = pof2 >> ++bits; + } + + this.numBits = bits; + + this.ratio = ratioToPowerOf2(durationMillis); + + int cleanupsPerBucketDuration = (durationMillis >= 60_000) ? 6 : 3; + Thread mt = new MaintenanceThread(durationMillis / cleanupsPerBucketDuration); + mt.start(); + } + + /** + * increments the counter for the passed identifier in the current time + * bucket and returns the new value + * + * @param identifier an identifier for which we want to maintain count, e.g. IP Address + * @return the count within the current time bucket + */ + public final int increment(String identifier) { + String key = getCurrentBucketPrefix() + "-" + identifier; + AtomicInteger ai = map.computeIfAbsent(key, v -> new AtomicInteger()); + return ai.incrementAndGet(); Review Comment: One idea that I had was to allow to configure certain paths with a different "weight", rather than configure a different Filter for different path, e.g. while requests to the homepage are counted as 1, a request for a login page might count as 10. That way, you can configure the Filter for 300 requests per minute, for example, which will allow for 300 requests to most of the site, but only 30 requests to the login page, mitigating brute force attacks that try to guess a password. If we do that then `updateAndGet()` might be more applicable, but again, I want to introduce this filter and get some feedback before adding more features to it. Also, we have another thread on the PR about back porting this feature, and if we decide to go all the way back to Tomcat 8.5 then this would be another one of the things that needs to be rewritten to run on Java 7. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: dev-unsubscr...@tomcat.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@tomcat.apache.org For additional commands, e-mail: dev-h...@tomcat.apache.org
