dajac commented on a change in pull request #9114:
URL: https://github.com/apache/kafka/pull/9114#discussion_r465997624



##########
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:
       i have removed the "and this". Does it parse better?




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