Lianet Magrans created KAFKA-17726:
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Summary: 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
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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