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https://issues.apache.org/jira/browse/KAFKA-17103?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17864380#comment-17864380
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Greg Harris commented on KAFKA-17103:
-------------------------------------
Also it's possible that there's an existing mechanism in MockClient for
performing this sort of thing, or an existing method that can be modified. I'm
not sure exactly why these particular tests have this flaw, as it seems like
providing metadata updates would be a fairly natural thing to mock out.
> MockClient tight loops when no metadata is present in KafkaProducerTest
> -----------------------------------------------------------------------
>
> Key: KAFKA-17103
> URL: https://issues.apache.org/jira/browse/KAFKA-17103
> Project: Kafka
> Issue Type: Test
> Components: clients
> Reporter: Greg Harris
> Priority: Minor
> Labels: newbie
>
> MockClient can throw this exception:
> {noformat}
> [2024-07-09 13:19:33,574] ERROR [Producer clientId=producer-1] Uncaught error
> in kafka producer I/O thread:
> (org.apache.kafka.clients.producer.internals.Sender:253)
> java.lang.IllegalStateException: No previous metadata update to use
> at
> org.apache.kafka.clients.MockClient$DefaultMockMetadataUpdater.updateWithCurrentMetadata(MockClient.java:700)
> at org.apache.kafka.clients.MockClient.poll(MockClient.java:323)
> at
> org.apache.kafka.clients.producer.internals.Sender.runOnce(Sender.java:349)
> at org.apache.kafka.clients.producer.internals.Sender.run(Sender.java:251)
> at java.base/java.lang.Thread.run(Thread.java:829){noformat}
> This happens whenever the MockClient.DefaultMockMetadataUpdater#lastUpdate
> variable is null, which is the case whenever there has not been any mock
> metadata update.
> In practice, this appears to happen in
> KafkaProducerTest#testTopicExpiryInMetadata,
> KafkaProducerTest#testTopicRefreshInMetadata,
> KafkaProducerTest#testTopicNotExistingInMetadata. These three tests also use
> busy-waiting to have another thread wait for the metadata update request and
> then provide the metadata update.
> We should find some mechanism to allow mocking these metadata updates that
> avoids this busy waiting/tight looping pattern, as it introduces an
> opportunity for nondeterminism and wastes CPU cycles.
> The solution should remove any usage of Thread.sleep/Utils.sleep/Time.SYSTEM.
> Ideally the solution wouldn't require an additional test thread, but this is
> optional.
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