[KAFKA-14848] KafkaConsumer incorrectly passes locally-scoped deserializers to FetchConfig

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.5.0
• Fix Version/s: 3.5.0
• Component/s: clients, consumer
• Labels: consumer-threading-refactor
• Assignee: Kirk True
• Reporter: Kirk True
• Created: 25/Mar/23 23:32
• Updated: 04/Oct/23 16:52
• Resolved: 25/Apr/23 22:08

Description

rayokota found some NullPointerExceptions that originate because of a recently introduced error in the KafkaConsumer constructor. The code was changed to pass the deserializer variables into the FetchConfig constructor. However, this code change incorrectly used the locally-scoped variables, not the instance-scoped variables. Since the locally-scoped variables could be null, this results in the FetchConfig storing null references, leading to downstream breakage.

Suggested change:

- FetchConfig<K, V> fetchConfig = new FetchConfig<>(config, keyDeserializer, valueDeserializer, isolationLevel);
+ FetchConfig<K, V> fetchConfig = new FetchConfig<>(config, this.keyDeserializer, this.valueDeserializer, isolationLevel);

Issue Links

• is caused by: KAFKA-14365 Extract common logic from Fetcher
• links to: GitHub Pull Request #13452