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https://issues.apache.org/jira/browse/KAFKA-13448?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jun Rao resolved KAFKA-13448.
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Fix Version/s: 3.2.0
Assignee: Philip Nee
Resolution: Fixed
merged [https://github.com/apache/kafka/pull/11689] and a followup fix
[https://github.com/apache/kafka/pull/12064] to trunk and 3.2 branch.
> Kafka Producer Client Callback behaviour does not align with Javadoc
> --------------------------------------------------------------------
>
> Key: KAFKA-13448
> URL: https://issues.apache.org/jira/browse/KAFKA-13448
> Project: Kafka
> Issue Type: Bug
> Components: clients
> Affects Versions: 1.1.0
> Reporter: Seamus O Ceanainn
> Assignee: Philip Nee
> Priority: Minor
> Fix For: 3.2.0
>
>
> In PR [#4188|https://github.com/apache/kafka/pull/4188] as part of
> KAFKA-6180, a breaking change was accidentally introduced in the behaviour of
> Callbacks for the producer client.
> Previously, whenever an exception was thrown when producing an event, the
> value for 'metadata' passed to the Callback.onCompletion method was always
> null. In PR [#4188|https://github.com/apache/kafka/pull/4188], in one part of
> the code where Callback.onCompletion is called, the behaviour was changed so
> that instead of passing a null value for metadata, a 'placeholder' value was
> provided instead (see
> [here|https://github.com/apache/kafka/pull/4188/files#diff-42d8f5166459ee28f201ff9cec0080fc7845544a0089ac9e8f3e16864cc1193eR1196]
> and
> [here|https://github.com/apache/kafka/pull/4188/files#diff-42d8f5166459ee28f201ff9cec0080fc7845544a0089ac9e8f3e16864cc1193eR1199]).
> This placeholder contained only topic and partition information, and with
> all other fields set to '-1'.
> This change only impacted a subset of exceptions, so that in the case of
> ApiExceptions metadata would still be null (see
> [here|https://github.com/apache/kafka/commit/aa42a11dfd99ee9ab24d2e9a7521ef1c97ae1ff4#diff-42d8f5166459ee28f201ff9cec0080fc7845544a0089ac9e8f3e16864cc1193eR843]),
> but for all other exceptions the placeholder value would be used. The
> behaviour at the time of writing remains the same.
> This issue was first reported in KAFKA-7412 when a user first noticed the
> difference between the documented behaviour of Callback.onCompletion and the
> implemented behaviour.
> At the time it was assumed that the behaviour when errors occur was to always
> provide a placeholder metadata value to Callback.onCompletion, and the
> documentation was updated at that time to reflect this assumption in [PR
> #5798|https://github.com/apache/kafka/pull/5798]. The documentation now
> states that when an exception occurs that the method will be called with an
> empty metadata value (see
> [here|https://github.com/apache/kafka/blob/3.1/clients/src/main/java/org/apache/kafka/clients/producer/Callback.java#L30-L31]).
> However, there is still one case where Callback.onCompletion is called with
> a null value for metadata (see
> [here|https://github.com/apache/kafka/blob/3.1/clients/src/main/java/org/apache/kafka/clients/producer/KafkaProducer.java#L1002]),
> so there is still a discrepancy between the documented behaviour and the
> implementation of Callback.onCompletion.
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