junrao commented on a change in pull request #9114: URL: https://github.com/apache/kafka/pull/9114#discussion_r465989800
########## File path: clients/src/main/java/org/apache/kafka/common/metrics/stats/TokenBucket.java ########## @@ -0,0 +1,101 @@ +/* + * 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.kafka.common.metrics.stats; + +import java.util.concurrent.TimeUnit; +import org.apache.kafka.common.metrics.MeasurableStat; +import org.apache.kafka.common.metrics.MetricConfig; +import org.apache.kafka.common.metrics.Quota; + +import static org.apache.kafka.common.metrics.internals.MetricsUtils.convert; + +/** + * The {@link TokenBucket} is a {@link MeasurableStat} implementing a token bucket algorithm + * that is usable within a {@link org.apache.kafka.common.metrics.Sensor}. + * + * The {@link Quota#bound()} defined the refill rate of the bucket while the maximum burst or + * the maximum number of credits of the bucket is defined by + * {@link MetricConfig#samples() * MetricConfig#timeWindowMs() * Quota#bound()}. + * + * The quota is considered as exhausted when the amount of remaining credits in the bucket + * is below zero. The enforcement is done by the {@link org.apache.kafka.common.metrics.Sensor}. + * + * Token Bucket vs Rate based Quota: + * The current sampled rate based quota does not cope well with bursty workloads. The issue is + * that a unique and large sample can hold the average above the quota and this until it is Review comment: "this until it is" doesn't quite parse. ########## File path: clients/src/main/java/org/apache/kafka/common/metrics/stats/TokenBucket.java ########## @@ -0,0 +1,101 @@ +/* + * 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.kafka.common.metrics.stats; + +import java.util.concurrent.TimeUnit; +import org.apache.kafka.common.metrics.MeasurableStat; +import org.apache.kafka.common.metrics.MetricConfig; +import org.apache.kafka.common.metrics.Quota; + +import static org.apache.kafka.common.metrics.internals.MetricsUtils.convert; + +/** + * The {@link TokenBucket} is a {@link MeasurableStat} implementing a token bucket algorithm + * that is usable within a {@link org.apache.kafka.common.metrics.Sensor}. + * + * The {@link Quota#bound()} defined the refill rate of the bucket while the maximum burst or + * the maximum number of credits of the bucket is defined by + * {@link MetricConfig#samples() * MetricConfig#timeWindowMs() * Quota#bound()}. + * + * The quota is considered as exhausted when the amount of remaining credits in the bucket + * is below zero. The enforcement is done by the {@link org.apache.kafka.common.metrics.Sensor}. + * + * Token Bucket vs Rate based Quota: + * The current sampled rate based quota does not cope well with bursty workloads. The issue is + * that a unique and large sample can hold the average above the quota and this until it is + * discarded. Practically, when this happens, one must wait until the sample is expired to + * bring the rate below the quota even though less time would be theoretically required. As an + * examples, let's imagine that we have: + * - Quota (Q) = 5 + * - Samples (S) = 100 + * - Window (W) = 1s + * A burst of 560 brings the average rate (R) to 5.6 (560 / 100). The throttle time is computed as Review comment: "The throttle time " : I guess this is the expected throttle time? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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