[jira] [Assigned] (KAFKA-5600) Group loading regression causing stale metadata/offsets cache

["Ismael Juma (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-5600?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ismael Juma reassigned KAFKA-5600:
----------------------------------

    Assignee: Jan Burkhardt

> Group loading regression causing stale metadata/offsets cache
> -------------------------------------------------------------
>
>                 Key: KAFKA-5600
>                 URL: https://issues.apache.org/jira/browse/KAFKA-5600
>             Project: Kafka
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 0.10.2.1, 0.11.0.0
>         Environment: any
>            Reporter: Jan Burkhardt
>            Assignee: Jan Burkhardt
>            Priority: Critical
>              Labels: regression, reliability
>             Fix For: 0.11.0.1, 0.11.1.0
>
>         Attachments: KafkaErrorConsumer.java, KafkaErrorProducer.java
>
>
> After long investigation we found a Problem in Kafka.
> When a __consumer_offsets partition gets segmented and Kafka is restarted and needs to reload offsets, consumers will start at a wrong position when metadata and offset events are in both segments.
> Reproduction:
> 1.) Start zookeeper and kafka as is from the archive
> {code}
> KAFKA_HEAP_OPTS="-Xmx256M -Xms256M" bin/zookeeper-server-start.sh config/zookeeper.properties
> KAFKA_HEAP_OPTS="-Xmx256M -Xms256M" bin/kafka-server-start.sh config/server.properties
> {code}
> 2.) Start [^KafkaErrorProducer.java] which adds 1M log entries to the topic test
> 3.) Start [^KafkaErrorConsumer.java] which starts a consumer, reads 100 entries one by one and then closes the consumer. This leads to a 2nd segment in /tmp/kafka-logs/__consumer_offsets-27. This step takes some time (around 5mins). The close of the consumer is needed to have metadata events in the segments too.
> 4.) Stop and restart the Kafka broker
> 5.) Start any consumer on topic test and group testgroup
> {code}
> bin/kafka-console-consumer.sh --from-beginning --bootstrap-server localhost:9092 --topic test --consumer-property group.id=testgroup
> {code}
> Is:
> the consumer starts at the segmentation boundary
> Expected:
> the consumer starts at the end
> The Reason for this behavior is the closing brace of the while loop in GroupMetadataManager#loadGroupsAndOffsets at a wrong position introduced with commit https://github.com/apache/kafka/commit/5bd06f1d542e6b588a1d402d059bc24690017d32
> I will prepare a pull request.
> *Edit*: The issue can happen if there are multiple reads from the same segment, see https://github.com/apache/kafka/pull/3538#discussion_r127759694



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