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https://issues.apache.org/jira/browse/KAFKA-3310?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15173223#comment-15173223
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Aditya Auradkar commented on KAFKA-3310:
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[~junrao] - Just making sure, you observe that the response is still delayed
right? The throttle time sensor is the last thing that is recorded and the
element has been added to the delay queue, so the fetchResponseCallback should
fire after the throttle time.
> fetch requests can trigger repeated NPE when quota is enabled
> -------------------------------------------------------------
>
> Key: KAFKA-3310
> URL: https://issues.apache.org/jira/browse/KAFKA-3310
> Project: Kafka
> Issue Type: Bug
> Affects Versions: 0.9.0.1
> Reporter: Jun Rao
>
> We saw the following NPE when consumer quota is enabled. NPE is triggered on
> every fetch request from the client.
> java.lang.NullPointerException
> at
> kafka.server.ClientQuotaManager.recordAndMaybeThrottle(ClientQuotaManager.scala:122)
> at
> kafka.server.KafkaApis.kafka$server$KafkaApis$$sendResponseCallback$3(KafkaApis.scala:419)
> at
> kafka.server.KafkaApis$$anonfun$handleFetchRequest$1.apply(KafkaApis.scala:436)
> at
> kafka.server.KafkaApis$$anonfun$handleFetchRequest$1.apply(KafkaApis.scala:436)
> at kafka.server.ReplicaManager.fetchMessages(ReplicaManager.scala:481)
> at kafka.server.KafkaApis.handleFetchRequest(KafkaApis.scala:431)
> at kafka.server.KafkaApis.handle(KafkaApis.scala:69)
> at kafka.server.KafkaRequestHandler.run(KafkaRequestHandler.scala:60)
> at java.lang.Thread.run(Thread.java:745)
> One possible cause of this is the logic of removing inactive sensors.
> Currently, in ClientQuotaManager, we create two sensors per clientId: a
> throttleTimeSensor and a quotaSensor. Each sensor expires if it's not
> actively updated for 1 hour. What can happen is that initially, the quota is
> not exceeded. So, quotaSensor is being updated actively, but
> throttleTimeSensor is not. At some point, throttleTimeSensor is removed by
> the expiring thread. Now, we are in a situation that quotaSensor is
> registered, but throttleTimeSensor is not. Later on, if the quota is
> exceeded, we will hit the above NPE when trying to update throttleTimeSensor.
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