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https://issues.apache.org/jira/browse/BEAM-1573?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15896989#comment-15896989
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Eugene Kirpichov commented on BEAM-1573:
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At a conference right now, but quick comment: yes, as Raghu said, we're getting
rid of Coder's as a general parsing mechanism. Use of coders for the purpose
for which KafkaIO currently uses them is explicitly forbidden by the Beam
PTransform Style Guide
https://beam.apache.org/contribute/ptransform-style-guide/#coders .
We should replace that with having KafkaIO return byte[] and having convenience
utilities for deserializing these byte[] using Kafka deserializers, e.g. by
wrapping the code Raghu posted as a utility in the kafka module (packaged, say,
as a SerializableFunction).
Raghu or @peay, perhaps consider sending a PR to fix this? It seems like it
should be rather easy. Though it would merit a short discussion on
[email protected] first.
> KafkaIO does not allow using Kafka serializers and deserializers
> ----------------------------------------------------------------
>
> Key: BEAM-1573
> URL: https://issues.apache.org/jira/browse/BEAM-1573
> Project: Beam
> Issue Type: Bug
> Components: sdk-java-extensions
> Affects Versions: 0.4.0, 0.5.0
> Reporter: peay
> Assignee: Raghu Angadi
> Priority: Minor
>
> KafkaIO does not allow to override the serializer and deserializer settings
> of the Kafka consumer and producers it uses internally. Instead, it allows to
> set a `Coder`, and has a simple Kafka serializer/deserializer wrapper class
> that calls the coder.
> I appreciate that allowing to use Beam coders is good and consistent with the
> rest of the system. However, is there a reason to completely disallow to use
> custom Kafka serializers instead?
> This is a limitation when working with an Avro schema registry for instance,
> which requires custom serializers. One can write a `Coder` that wraps a
> custom Kafka serializer, but that means two levels of un-necessary wrapping.
> In addition, the `Coder` abstraction is not equivalent to Kafka's
> `Serializer` which gets the topic name as input. Using a `Coder` wrapper
> would require duplicating the output topic setting in the argument to
> `KafkaIO` and when building the wrapper, which is not elegant and error prone.
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