/*
* 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 an 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 final int bucketDuration;
/**
* Creates a new TimeBucketCounter with the specified lifetime.
*
* @param bucketDuration duration in seconds, e.g. for 1 minute pass 60
* @param executorService the executor service that will be used to run the maintenance task
*
* @throws NullPointerException if executorService is <code>null</code>.
*/
public TimeBucketCounterBase(int bucketDuration, ScheduledExecutorService executorService) {
Objects.requireNonNull(executorService);
this.executorService = executorService;
this.bucketDuration = bucketDuration;
int cleanupsPerBucketDuration = (bucketDuration >= 60) ? 6 : 3;
sleeptime = bucketDuration * 1000L / 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
*/
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.
*
* @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
*/
public 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
*/
public abstract long getMillisUntilNextBucket();
/**
* Stops threads created by this object and cleans up resources.
*/
public void destroy() {
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() {
/*
* The implementation of this method assumes that the time taken for eviction is less than 1 bucket duration. It
* is possible that the eviction process starts in one bucket but finishes in another. Therefore, keys for the
* current bucket and the next bucket when the eviction process starts are excluded from eviction.
*/
long currentBucketIndex = getCurrentBucketPrefix();
String currentBucketPrefix = String.valueOf(currentBucketIndex);
String nextBucketPrefix = String.valueOf(currentBucketIndex + 1);
ConcurrentHashMap.KeySetView<String,AtomicInteger> keys = map.keySet();
// remove obsolete keys
keys.removeIf(k -> !k.startsWith(currentBucketPrefix) && !k.startsWith(nextBucketPrefix));
}
private class Maintenance implements Runnable {
@Override
public void run() {
periodicEvict();
}
}
private class MaintenanceMonitor implements Runnable {
@Override
public void run() {
if (sleeptime > 0 && (maintenanceFuture == null || maintenanceFuture.isDone())) {
if (maintenanceFuture != null && maintenanceFuture.isDone()) {
// There was an error executing the scheduled task, get it and log it
try {
maintenanceFuture.get();
} catch (InterruptedException | ExecutionException e) {
log.error(sm.getString("timebucket.maintenance.error"), e);
}
}
maintenanceFuture = executorService.scheduleWithFixedDelay(new Maintenance(), sleeptime, sleeptime,
TimeUnit.MILLISECONDS);
}
}
}
}