Kafka

KIP Implementation

• KIP is the source of truth — config names, default values, descriptions, and behavior must match the KIP exactly
• Always cross-check config defaults, types, and valid values against the KIP before implementing

Config Deprecation

• When marking @Deprecated, check all related constants (_CONFIG, _DOC, _DEFAULT), not just some
• After adding @Deprecated(forRemoval = true), check all Java files referencing the constant for build warnings; add @SuppressWarnings("removal") where needed
• Guard deprecation warning messages with doLog to avoid duplicate output during broker startup

Code Review

• Packages with package-info.java are public API — pay extra attention to backward compatibility (e.g. removing configs, constructors, or method signatures)
• Commit messages can be brief — PRs are squash-merged in Apache Kafka

Coding Conventions

• Scala constants use LikeThis, not LIKE_THIS
• Log messages: complete sentences, no class names or internal variable names
• Wrap DEBUG/TRACE logging with isDebugEnabled/isTraceEnabled
• Config values should reflect the user's mental model, not internal implementation details
• Streams API: use final on class members, local variables, loop variables, and method parameters
• Streams API: test methods follow shouldXxx() naming (e.g. shouldNotAcceptNullAsTopicName())

Testing

• Never use sleep() — use injected kafka.utils.Time and advance the clock programmatically
• Never hard-code ports — use TestUtils.choosePort() for free port allocation

Apache Mailing List

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• Use the Pony Mail API instead: thread.lua?id=<id> and email.lua?id=<mid> at lists.apache.org/api/