[KafkaIO] Remove build support for Kafka clients before 3.9.2#39284
[KafkaIO] Remove build support for Kafka clients before 3.9.2#39284sjvanrossum wants to merge 7 commits into
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Summary of ChangesHello, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request modernizes the KafkaIO module by standardizing on Kafka client version 3.9.2. By removing support for older client versions, the project reduces maintenance overhead and enables the adoption of newer Kafka features. The changes involve updating Gradle build configurations, removing deprecated sub-projects, and adjusting test infrastructure to align with the updated Kafka server APIs. Highlights
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Code Review
This pull request upgrades the Kafka dependency version from 2.4.1 to 3.9.2, cleans up several legacy Kafka integration test modules, and adapts the codebase to Kafka's updated APIs (such as replacing KafkaServerStartable with KafkaServer and updating consumer close signatures). The reviewer's feedback highlights a critical improvement: instead of using fragile, Scala-compiler-generated default argument methods (like $lessinit$greater$default$2()) directly in Java when initializing KafkaServer, the code should explicitly pass standard Scala/Java instances to ensure stability across compiler versions.
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| KafkaServer server = | ||
| new KafkaServer( | ||
| new KafkaConfig(props), | ||
| KafkaServer.$lessinit$greater$default$2(), | ||
| KafkaServer.$lessinit$greater$default$3(), | ||
| KafkaServer.$lessinit$greater$default$4()); |
There was a problem hiding this comment.
Using Scala compiler-generated default argument methods (like $lessinit$greater$default$2()) directly in Java is fragile and highly discouraged. These synthetic methods are internal implementation details of the Scala compiler and can change across Scala compiler versions or if the constructor parameters are reordered/modified in future Kafka releases.
Instead, pass explicit, standard Scala/Java instances such as org.apache.kafka.common.utils.Time.SYSTEM, scala.Option.empty(), and scala.collection.immutable.List$.MODULE$.empty().
| KafkaServer server = | |
| new KafkaServer( | |
| new KafkaConfig(props), | |
| KafkaServer.$lessinit$greater$default$2(), | |
| KafkaServer.$lessinit$greater$default$3(), | |
| KafkaServer.$lessinit$greater$default$4()); | |
| KafkaServer server = | |
| new KafkaServer( | |
| new KafkaConfig(props), | |
| org.apache.kafka.common.utils.Time.SYSTEM, | |
| scala.Option.empty(), | |
| scala.collection.immutable.List$.MODULE$.empty()); |
There was a problem hiding this comment.
Using Scala compiler-generated default argument methods (like $lessinit$greater$default$2()) directly in Java is fragile and highly discouraged.
Needs citation?
Jokes aside, that last argument is supposed to be a Boolean so this is not exactly the right suggestion.
I don't feel strongly about this, Kafka itself instantiates KafkaServer as follows in main:
new KafkaServer(
config,
Time.SYSTEM,
threadNamePrefix = None,
enableForwarding = enableApiForwarding(config)
)Other than readability I don't see a good reason not to use the generated methods to access default arguments.
If the signature were to change due to argument reordering as mentioned, then the suggested change would break at compile time whereas the generated methods would return the expected type because their definition depends on the signature definition itself.
| server = | ||
| new KafkaServer( | ||
| KafkaConfig.fromProps(kafkaProperties), | ||
| KafkaServer.$lessinit$greater$default$2(), | ||
| KafkaServer.$lessinit$greater$default$3(), | ||
| KafkaServer.$lessinit$greater$default$4()); |
There was a problem hiding this comment.
Using Scala compiler-generated default argument methods (like $lessinit$greater$default$2()) directly in Java is fragile and highly discouraged. These synthetic methods are internal implementation details of the Scala compiler and can change across Scala compiler versions or if the constructor parameters are reordered/modified in future Kafka releases.
Instead, pass explicit, standard Scala/Java instances such as org.apache.kafka.common.utils.Time.SYSTEM, scala.Option.empty(), and scala.collection.immutable.List$.MODULE$.empty().
| server = | |
| new KafkaServer( | |
| KafkaConfig.fromProps(kafkaProperties), | |
| KafkaServer.$lessinit$greater$default$2(), | |
| KafkaServer.$lessinit$greater$default$3(), | |
| KafkaServer.$lessinit$greater$default$4()); | |
| server = | |
| new KafkaServer( | |
| KafkaConfig.fromProps(kafkaProperties), | |
| org.apache.kafka.common.utils.Time.SYSTEM, | |
| scala.Option.empty(), | |
| scala.collection.immutable.List$.MODULE$.empty()); |
There was a problem hiding this comment.
Using Scala compiler-generated default argument methods (like $lessinit$greater$default$2()) directly in Java is fragile and highly discouraged.
Needs citation?
Jokes aside, that last argument is supposed to be a Boolean so this is not exactly the right suggestion.
I don't feel strongly about this, Kafka itself instantiates KafkaServer as follows in main:
new KafkaServer(
config,
Time.SYSTEM,
threadNamePrefix = None,
enableForwarding = enableApiForwarding(config)
)Other than readability I don't see a good reason not to use the generated methods to access default arguments.
If the signature were to change due to argument reordering as mentioned, then the suggested change would break at compile time whereas the generated methods would return the expected type because their definition depends on the signature definition itself.
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Remove build support for legacy Kafka clients. The Kafka protocol implementation in Kafka client version 3.9.2 still allows users to connect to legacy Kafka brokers. See KIP-896 for details on protocol compatibility.
This PR was split from #36834 and enables opportunities to improve KafkaIO performance by leveraging new client features.
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