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https://issues.apache.org/jira/browse/KAFKA-17726?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Lianet Magrans resolved KAFKA-17726.
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Reviewer: Lianet Magrans
Resolution: Fixed
> New consumer subscribe/subscribeFromPattern in background thread
> ----------------------------------------------------------------
>
> Key: KAFKA-17726
> URL: https://issues.apache.org/jira/browse/KAFKA-17726
> Project: Kafka
> Issue Type: Bug
> Components: clients, consumer
> Reporter: Lianet Magrans
> Assignee: PoAn Yang
> Priority: Major
> Labels: consumer-threading-refactor, kip-848-client-support
> Fix For: 4.0.0
>
>
> There are still some calls to change the subscriptionState subscription in
> the app thread, that could lead to race-conditions given that the
> subscription state object is shared between the background and app thread and
> is mostly updated in the background. We should consider moving the
> subscriptionState.subscribe() and subscribeFromPattern calls to the
> background.
> [https://github.com/apache/kafka/blob/5624bc7c7e43339eb64e18491ac5039324e50678/clients/src/main/java/org/apache/kafka/clients/consumer/internals/AsyncKafkaConsumer.java#L1465]
> [https://github.com/apache/kafka/blob/5624bc7c7e43339eb64e18491ac5039324e50678/clients/src/main/java/org/apache/kafka/clients/consumer/internals/AsyncKafkaConsumer.java#L1703]
> [https://github.com/apache/kafka/blob/5624bc7c7e43339eb64e18491ac5039324e50678/clients/src/main/java/org/apache/kafka/clients/consumer/internals/AsyncKafkaConsumer.java#L1736]
> One option would be to use the existing SubscriptionChangeEvent, perform the
> subscription (and metadata) changes in the AppEventProcessor (where
> unsubscribe already takes place).
> Note that these calls are closely related to metadata object calls, to
> request metadata for new topics and "maybeUpdateSubscriptionMetadata". We
> should maybe consider moving them together to the background (where the
> metadata object is also updated).
> [https://github.com/apache/kafka/blob/5624bc7c7e43339eb64e18491ac5039324e50678/clients/src/main/java/org/apache/kafka/clients/consumer/internals/AsyncKafkaConsumer.java#L1703-L1705]
>
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