Chenjp commented on code in PR #794: URL: https://github.com/apache/tomcat/pull/794#discussion_r1986702168
########## java/org/apache/catalina/util/TimeBucketCounterBase.java: ########## @@ -0,0 +1,214 @@ +/* + * 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.Objects; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ExecutionException; +import java.util.concurrent.ScheduledExecutorService; +import java.util.concurrent.ScheduledFuture; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicInteger; + +import org.apache.juli.logging.Log; +import org.apache.juli.logging.LogFactory; +import org.apache.tomcat.util.res.StringManager; + +/** + * 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 integer value. each time the increment() method is called it adds the key if it does not exist, + * increments its value and returns it. + */ +public abstract class TimeBucketCounterBase { + + private static final Log log = LogFactory.getLog(TimeBucketCounterBase.class); + private static final StringManager sm = StringManager.getManager(TimeBucketCounterBase.class); + + private static final String BUCKET_KEY_DELIMITER = "^"; + /** + * Map to hold the buckets + */ + private final ConcurrentHashMap<String,AtomicInteger> map = new ConcurrentHashMap<>(); + + /** + * /** The future allowing control of the background processor. + */ + private ScheduledFuture<?> maintenanceFuture; + private ScheduledFuture<?> monitorFuture; + private final ScheduledExecutorService executorService; + private final long sleeptime; + private int bucketDuration; + + /** + * Creates a new TimeBucketCounter with the specified lifetime. + * + * @param utilityExecutor the executor that should be used to handle maintenance task. + * @param bucketDuration duration in seconds, e.g. for 1 minute pass 60 + * + * @throws NullPointerException if executorService is <code>null</code>. + */ + public TimeBucketCounterBase(ScheduledExecutorService utilityExecutor, int bucketDuration) { + Objects.requireNonNull(utilityExecutor); + this.executorService = utilityExecutor; + this.bucketDuration = bucketDuration; + + int cleanupsPerBucketDuration = (bucketDuration >= 60) ? 6 : 3; + sleeptime = bucketDuration * 1000 / cleanupsPerBucketDuration; + + // Start our thread + if (sleeptime > 0) { + monitorFuture = executorService.scheduleWithFixedDelay(new MaintenanceMonitor(), 0, 60, TimeUnit.SECONDS); + } + } + + /** + * @return bucketDuration in seconds + */ + public int getBucketDuration() { + return bucketDuration; + } + + /** + * Returns the ratio between the configured duration param and the actual duration. + * @return the ratio between the configured duration param and the actual duration. + */ + public abstract double getRatio(); + + /** + * 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 + * + * @see TimeBucketCounterBase#genKey(String) + */ + public final int increment(String identifier) { + String key = genKey(identifier); + AtomicInteger ai = map.computeIfAbsent(key, v -> new AtomicInteger()); + return ai.incrementAndGet(); + } + + /** + * Generates the key of timeBucket counter maps with the specific identifier, and the timestamp is implicitly + * equivalent to "now". + * + * @param identifier an identifier for which we want to maintain count + * + * @return key of timeBucket counter maps + */ + protected final String genKey(String identifier) { + return genKey(identifier, System.currentTimeMillis()); + } + + /** + * Generates the key of timeBucket counter maps with the specific identifier and timestamp. + * + * @param identifier of target request + * @param timestamp when target request received + * + * @return key of timeBucket counter maps + */ + protected final String genKey(String identifier, long timestamp) { + return getBucketIndex(timestamp) + BUCKET_KEY_DELIMITER + identifier; + } + + /** + * Calculate the bucket index for the specific timestamp, concrete subclass. + * + * @param timestamp the specific timestamp in milliseconds + * + * @return prefix the bucket key prefix for the specific timestamp + */ + protected abstract long getBucketIndex(long timestamp); + + /** + * Returns current bucket prefix + * @return bucket index + */ + protected int getCurrentBucketPrefix() { + return (int)getBucketIndex(System.currentTimeMillis()); + } + /** + * When we want to test a full bucket duration we need to sleep until the next bucket starts. + * <p> + * <strong>WARNING:</strong> This method is used for test purpose. + * + * @return the number of milliseconds until the next bucket + */ + @Deprecated + public abstract long getMillisUntilNextBucket(); + + /** + * Destroy resources + */ + public void destroy() { + this.map.clear(); + if (monitorFuture != null) { + monitorFuture.cancel(true); + monitorFuture = null; + } + if (maintenanceFuture != null) { + maintenanceFuture.cancel(true); + maintenanceFuture = null; + } + } + + /** + * Periodic evict, perform removal of obsolete bucket items. Absence of this operation may result in OOM after a + * long run. + */ + public void periodicEvict() { + final long minBucketIndex = getBucketIndex(System.currentTimeMillis()); + // assume that elapsed time of periodicEvict less than 1x bucketDuration. + // to avoid extreme case: 999999-xxx vs 1000000-xxx + final long maxBucket = minBucketIndex + 2; + + final String minBucketPrefix = minBucketIndex + BUCKET_KEY_DELIMITER; + final String maxBucketPrefix = maxBucket + BUCKET_KEY_DELIMITER; + + // remove obsolete items whose key are less than minBucketPrefix and maxBucketPrefix in same time. + map.keySet().removeIf(k -> k.compareTo(minBucketPrefix) < 0 && k.compareTo(maxBucketPrefix) < 0); + } Review Comment: // assume that elapsed time of periodicEvict less than 1x bucketDuration. t1: last ns of current bucket index range. (bucket index: 999999), scheduler call periodicEvict() 10 ns later... t2: keyset removal start, and current bucket index: 1000000. should not remove keys startswith 1000000. -- 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
