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https://issues.apache.org/jira/browse/KAFKA-5244?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16010820#comment-16010820
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Ismael Juma commented on KAFKA-5244:
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Good find [~rsivaram]. Note that in https://github.com/apache/kafka/pull/2983,
I changed `BrokerTopicStats` to be a class. The underlying metrics are still a
singleton, but it means that we would recreate them on start-up of KafkaServer.
Maybe that fixes this issue?
> Tests which delete singleton metrics break subsequent metrics tests
> -------------------------------------------------------------------
>
> Key: KAFKA-5244
> URL: https://issues.apache.org/jira/browse/KAFKA-5244
> Project: Kafka
> Issue Type: Bug
> Components: core
> Reporter: Rajini Sivaram
> Assignee: Rajini Sivaram
> Fix For: 0.11.0.0
>
>
> Static metrics like {{BrokerTopicStats.ReplicationBytesInPerSec}} are created
> in a singleton, resulting in one metric being created in a JVM. Some tests
> like {{MetricsDuringTopicCreationDeletionTest}} delete all metrics from the
> static metrics registry. The singleton metrics don't get recreated and
> subsequent tests relying on these metrics may fail.
> Singleton metrics make testing hard - we have no idea what metrics are being
> tested. Not sure we want to change that though since there is a lot of code
> that relies on this. But we have to fix tests to ensure that metrics are left
> in a good state.
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