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/*
* 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.ScheduledExecutorService;
/**
* A RateLimiter that compromises efficiency for accuracy in order to provide exact rate limiting.
*/
public class ExactRateLimiter extends RateLimiterBase {
@Override
protected String getDefaultPolicyName() {
return "exact";
}
@Override
protected TimeBucketCounterBase newCounterInstance(int duration, ScheduledExecutorService executorService) {
return new ExactTimeBucketCounter(duration, executorService);
}
/**
* An accurate counter with exact bucket index, but slightly less efficient than another fast counter provided with
* the {@link FastRateLimiter}.
*/
static class ExactTimeBucketCounter extends TimeBucketCounterBase {
ExactTimeBucketCounter(int bucketDuration, ScheduledExecutorService executorService) {
super(bucketDuration, executorService);
}
@Override
public long getBucketIndex(long timestamp) {
return (timestamp / 1000) / getBucketDuration();
}
@Override
public double getRatio() {
// Actual value is exactly the same as declared
return 1.0d;
}
@Override
public long getMillisUntilNextBucket() {
long millis = System.currentTimeMillis();
long nextTimeBucketMillis = (getBucketIndex(millis) + 1) * getBucketDuration() * 1000;
return nextTimeBucketMillis - millis;
}
}
}
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