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Posted to jira@kafka.apache.org by "Olaf Gottschalk (Jira)" <ji...@apache.org> on 2021/02/05 12:47:00 UTC
[jira] [Created] (KAFKA-12297) Implementation of MockProducer
contradicts documentation of Callback for async send
Olaf Gottschalk created KAFKA-12297:
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Summary: Implementation of MockProducer contradicts documentation of Callback for async send
Key: KAFKA-12297
URL: https://issues.apache.org/jira/browse/KAFKA-12297
Project: Kafka
Issue Type: Bug
Components: producer , unit tests
Affects Versions: 2.7.0
Reporter: Olaf Gottschalk
In Unit tests, a MockProducer is used to imitate a real producer.
Using the errorNext(RuntimeException e) method, it is possible to indicate failures.
BUT: the asynchronous send method with a callback has a clear documentation of that callback interface, stating that Metadata will always be set, and never null.
{{The metadata for the record that was sent (i.e. the partition and offset). An empty metadata with -1 value for all fields except for topicPartition will be returned if an error occurred.}}
The bug is, that in MockProducer's Completion implementation the following happens:
{{if (e == null)}}
{{ callback.onCompletion(metadata, null);}}
{{else}}
{{ callback.onCompletion(null, e);}}
Behaving against the own documentation leads to very subtle bugs: tests that implement the error condition checking metadata != null will be fine, but in real life fail horribly.
A MockProducer should at all times behave exactly like the real thing and adhere to the documentation of the Callback!
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