Since graduation from the Apache Incubator some 2 years ago, Apache Flink has been thriving as a pioneering data streaming engine used in production across a wide range of organizations. Powering this momentum of growing traction is a community-wide effort driven by over 260 worldwide contributors (as of January 2017). This talk aims at providing information on the many ways that one can also join the community and start contributing to Flink. Like any other successful project, there are some simple guidelines for contributors to allow easier reviewing and pull request merging. We will go through the best practices of the contribution process, introducing the Apache Way of how the community collaborates, as well as some procedures that the community uses for discussions such as FLIPs (Flink Improvement Proposals). Another main objective of this talk is to promote parts of the project that are currently undergoing heavy development and is welcoming to extra pairs of helping hands.

1. Joining the Scurry of Squirrels:
Contributing to Apache Flink®
@tzulitai
tzulitai@apache.org
Tzu-Li (Gordon) Tai

2. Who?
▪ Apache Flink Committer
• Streaming connectors (Kafka, Kinesis, Elasticsearch)
▪ Software Engineer at data Artisans
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3. Who?
▪ Definitely not a veteran contributor of Apache Flink ;-)
3
… my life of Apache Flink contribution ;)

4. Who?
▪ Definitely not a veteran contributor of Apache Flink ;-)
4
… my life of Apache Flink contribution ;)

5. How can I contribute?
5
The usual first question ...

6. It never is just about the code ...
6

7. Different forms of Contribution
▪ As an user …
• file bug reports
• join discussions / propose new features on the mailing list
• testing release candidates
• talk about Flink
▪ As a developer …
• submit & review patches for features and fixes
• help answer user questions
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8. Mailing Lists, JIRA, and Wiki
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Know your resources!

9. Know your resources!
▪ The resources is the community, and where
everything happens
• Mailing lists
• JIRA
• Wiki
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10. Mailing lists
▪ Developer mailing list
• dev@flink.apache.org
• Ask questions about Flink development
• Discuss new Flink features
▪ User mailing list
• user@flink.apache.org
• General questions about using Flink
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11. JIRA board
▪ Issue tracking
• https://issues.apache.org/jira/browse/FLINK
• Where bugs and new features / improvements are filed
• All code contributions must always have a corresponding
JIRA issue ticket opened
• Do NOT ask questions here (--> mailing lists)
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12. Wiki
▪ General information about the project
• https://cwiki.apache.org/confluence/display/FLINK
• Mostly relevant for FLIPs (Flink Improvement Proposals)
• Other info somewhat outdated
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13. Apache Flink Patch Submission
13

14. Patch Submission Process
14
File and discuss
directly on JIRA
Start a discussion
on the developer
mailing list
FLIP
(Flink Improvement
Proposals)
Community
Consensus
Submit Github
pull request
Committer
merges patch
review & refine

15. Patch Submission Process
15
File and discuss
directly on JIRA
Start a discussion
on the developer
mailing list
FLIP
(Flink Improvement
Proposals)
Community
Consensus
Submit Github
pull request
Committer
merges patch
review & refine

16. The Apache Way: Community Over Code
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▪ Changes, especially new features, should be agreed upon
by the community
• Does not apply just to the developers
• Beneficial to users as a whole
▪ Always seek to reach some level of consensus throughout
the code contribution process
• Avoid needing to go back to feature discussion after coding

17. Patch Submission Process
17
File and discuss
directly on JIRA
Start a discussion
on the developer
mailing list
FLIP
(Flink Improvement
Proposals)
Community
Consensus
Submit Github
pull request
Committer
merges patch
review & refine

18. Filing a JIRA
18
▪ Always have a good description of what the issue is
• Bugs - the cause and the proposed solution
• Improvements and features - bootstrap potential discussion with the
implementation you have in mind
▪ Remember to appropriately set “Components”

19. Assign yourself to a JIRA
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▪ Set the “Assignee” field to yourself
• Notifies others that this issue is already in good hands
▪ Simply request JIRA permission on the developer mailing list

20. Patch Submission Process
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File and discuss
directly on JIRA
Start a discussion
on the developer
mailing list
FLIP
(Flink Improvement
Proposals)
Community
Consensus
Submit Github
pull request
Committer
merges patch
review & refine

21. FLIP (Flink Improvement Proposals)
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▪ Adopted from the Apache Kafka community
▪ Official design documentation for major features
• Serves as the basis of discussion on the dev mailing list
• Allows the community to decide on the best future-proof design

22. Patch Submission Process
22
File and discuss
directly on JIRA
Start a discussion
on the developer
mailing list
FLIP
(Flink Improvement
Proposals)
Community
Consensus
Submit Github
pull request
Committer
merges patch
review & refine

23. Patch Submission Best Practices
23
▪ Rebase onto latest master prior to opening pull request
• git pull --rebase origin master
▪ Squash your commits to appropriate set
▪ Commit message example:
• [FLINK-6025] [cep] Implement skip till next match strategy

24. Patch Submission Best Practices
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▪ Usually the pull request naming follows the primary
commit’s message:
• [FLINK-6025] [cep] Implement skip till next match strategy
▪ Address all discussions happening on the pull request
▪ Push follow-up commits
• Retain history of the patch review
• Also have meaningful msgs for follow-up commits

25. Patch Submission Process
25
File and discuss
directly on JIRA
Start a discussion
on the developer
mailing list
FLIP
(Flink Improvement
Proposals)
Community
Consensus
Submit Github
pull request
Committer
merges patch
review & refine

26. Closing
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27. Final Takeaways
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▪ Development of Apache Flink is heavily centered around its
community
• The Apache Way - community over code
• Contributing is never just about writing code
▪ Know the resources and do not hesitate to approach.
▪ Extra pair of helping hands is always welcome ;-) !

28. Shoutouts
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▪ Flink CEP
• Complex event processing
• Pattern detection for streams
• → If interested, contact
Kostas Kloudas (kkloudas@apache.org)
▪ Flink ML
• Online learning
• Incremental learning
• Model serving
• → If interested, contact
Theodore Vasiloudis (tvas@apache.org)

29. Thank you!
@tzulitai
@ApacheFlink
@dataArtisans