Jun Rao created KAFKA-3310:
------------------------------
Summary: 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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