This document provides guidance on contributing code to the Apache Kafka open source project. It discusses finding issues to work on, the development workflow including writing code and tests and opening pull requests, and the Kafka Improvement Proposal (KIP) process for proposing and discussing larger changes. The presenters are long-time Kafka contributors who provide their backgrounds and experiences. Guidelines are given for effective collaboration through mailing lists, documentation, and issue tracking. The goal is to help both new and experienced developers contribute value to the project.

1. Developer’s Guide to
Contributing Code to Kafka
Mickael Maison
Tom Bentley

2. Who are we?
Mickael
Contributor since 2016
Committer since 2019
PMC member since 2020
Tom
Contributor since 2017
Committer since 2021
PMC member since 2021

3. Apache Kafka: An Open Source Project

4. https://github.com/apache/kafka/blob/trunk/CONTRIBUTING.md
Become a contributor!

5. Collaboration
Dev Mailing List: https://kafka.apache.org/contact
Wiki: https://cwiki.apache.org/confluence/display/KAFKA/Index
Bug tracker: https://issues.apache.org/jira/projects/KAFKA/issues
Code: https://github.com/apache/kafka

6. “I just need to fix
this one bug”
“I just want to
contribute”
Finding something to work on

7. Finding something to work on
Long term
involvement
First
Contribution
Small
Changes
Large
Changes

8. Finding something to work on
Long term
involvement
First
Contribution
Small
Changes
Large
Changes

9. Contributing Code Changes
Issue Minor?

10. Contributing Code Changes
Issue PR
Minor?

11. Contributing Code Changes
Issue
JIRA
PR
Minor?
Same APIs?

12. Writing code and tests
https://github.com/apache/kafka/blob/trunk/README.md

13. Gradle Tasks
Compile: assemble
2 minutes
Build + run test: build
20-30 minutes
Run test on specific project: clients:test
variable
Run specific tests: core:test --tests "*PartitionTest"

14. Opening a Pull Request
Reviewers: https://kafka.apache.org/committers

15. Making a Change
Issue
JIRA
PR
Minor?
Same
APIs?
LGTM? Commit

16. Kafka Improvement Proposals
Issue
JIRA
PR
Minor?
Same
APIs?
LGTM? Commit
KIP

19. Idea & JIRA

20. Draft &
PoC
Idea & JIRA

21. Draft &
PoC
Discussion
Idea & JIRA

22. Draft &
PoC
Discussion
LGTM?
Idea & JIRA

23. Draft &
PoC
Discussion
LGTM? Voting
Idea & JIRA

24. Draft &
PoC
Discussion
LGTM? Voting
PR
Idea & JIRA
Accepted?

25. Anatomy of a KIP
Draft &
PoC
KIP Index lists all the KIPs, and their current state
Standard sections:
Status
Motivation
Public interfaces
Proposed changes
Compatibility, Deprecation, Migration
Test Plan
Rejected alternatives

26. Anatomy of a KIP - Status section
Draft &
PoC

27. Anatomy of a KIP - Motivation section
Example:
KIP-730: Producer ID generation in KRaft mode
Draft &
PoC

28. Anatomy of a KIP - Public interfaces
Example:
KIP-664 Provide tooling to detect and abort hanging transactions
Draft &
PoC

29. Anatomy of a KIP - Proposed changes
Example:
KIP-98: Exactly Once Delivery and Transactional Messaging
Draft &
PoC

30. Anatomy of a KIP - Compatibility, Deprecation, Migration
Example:
KIP-802 Validation Support for Kafka Connect SMT and
Converter Options
Draft &
PoC

31. Anatomy of a KIP - Test plan
Example:
None! This is new
Draft &
PoC

32. Anatomy of a KIP - Rejected alternatives
Example:
KIP-618: Exactly Once support for Source Connectors
Draft &
PoC

33. To: dev@kafka.apache.org
Subject: [DISCUSS] KIP-XXX: My great idea
Discussion

34. To: dev@kafka.apache.org
Subject: [VOTE] KIP-XXX: My great idea
Voting

36. Interminable discussion
Real problem?
Clear + strong motivation?
Too narrow?
Too broad?
Listened to feedback?

37. Contributing regularly

38. Thank you!
Key Resources:
https://kafka.apache.org/contributing
https://cwiki.apache.org/confluence/display/KAFKA/Kafka+Improvement+Proposals
https://kafka.apache.org/committers
https://github.com/apache/kafka