1. 2010 CloudBees, Inc. All Rights Reserved 2010 CloudBees, Inc. All Rights Reserved How we made the Jenkins community Kohsuke Kawaguchi Creator of Jenkins / Architect, CloudBees, Inc.

2. 2010 CloudBees, Inc. All Rights Reserved 22010 CloudBees, Inc. All Rights Reserved What is Jenkins? Java web application For builds, tests, and broader automation Called Continuous Integration server MIT-licensed, 8 years old jenkins-ci.org 3. 2010 CloudBees, Inc. All Rights Reserved 32010 CloudBees, Inc. All Rights Reserved Where we are today 53,000+ installations around the world 600+ plugins by 500 contributors #1 CI server in the market 4. 2010 CloudBees, Inc. All Rights Reserved 42010 CloudBees, Inc. All Rights Reserved How did we come this far? All the usual things Software that works Being at the right place at the right time But Id like to think theres more to it And its something I think others can replicate 5. 2010 CloudBees, Inc. All Rights Reserved 52010 CloudBees, Inc. All Rights Reserved Communication is inherently painful Ask if the project likes the change Im thinking Work on the change Submit the patch and ask for approval Defend the patch and revise it Docs, tests, IP assignment Done 6. 2010 CloudBees, Inc. All Rights Reserved 62010 CloudBees, Inc. All Rights Reserved Programmers are picky bunch All sorts of things to quarrel about Should { be on the same line as if? Different taste for design trade-off Different anticipation for future expansions Hardly bearable even when you know them personally 7. 2010 CloudBees, Inc. All Rights Reserved 72010 CloudBees, Inc. All Rights Reserved More so in FLOSS We dont know each other No relationship outside coding No common goals No command structure Time zone / language barrier 8. 2010 CloudBees, Inc. All Rights Reserved 82010 CloudBees, Inc. All Rights Reserved Communication is root of all evil Less, the better Get rid of the need for it Dont stand in the way of people and their itches Innovations happen everywhere. Dont kill them before it materializes 9. 2010 CloudBees, Inc. All Rights Reserved 92010 CloudBees, Inc. All Rights Reserved The Question 10. 2010 CloudBees, Inc. All Rights Reserved 102010 CloudBees, Inc. All Rights Reserved It starts with modularity It means: Large software, divided into small silos Module interaction controlled by contracts Code/build/test at module level Modularity enables extensibility 11. 2010 CloudBees, Inc. All Rights Reserved 112010 CloudBees, Inc. All Rights Reserved Extensibility! Open up to the rest of the world The only thing that really matters It enables all kinds of social/technical tricks Its not free, but its worth the effort 12. 2010 CloudBees, Inc. All Rights Reserved 122010 CloudBees, Inc. All Rights Reserved #0: Programmability / Scriptability Every software should be a library Let other programs talk to your program Theres always a layer above you App people tend to forget this ImageMagick vs Gimp 13. 2010 CloudBees, Inc. All Rights Reserved 132010 CloudBees, Inc. All Rights Reserved #1: Code loading at runtime Define extension points Contracts to be followed by extensions Discovering implementations Java, etc. requires some work Provide isolation 14. 2010 CloudBees, Inc. All Rights Reserved 142010 CloudBees, Inc. All Rights Reserved #2: Treat extensions as 1st class citizen If core can do something that extensions cant, thats a bug If users can tell apart extensions from core, you arent doing enough 15. 2010 CloudBees, Inc. All Rights Reserved 152010 CloudBees, Inc. All Rights Reserved #3: Data model extensibility Extensions need to be able to store stuff By adding stuff to core domain objects By adding more domain objects For Jenkins, XML really helped Schema versioning becomes non-linear 16. 2010 CloudBees, Inc. All Rights Reserved 162010 CloudBees, Inc. All Rights Reserved #4: Embrace heterogeneousness Good contract enables multiple impls Take something, slightly change something, and you have a new extension impl You see a list, I see extensibility And inheritance This is surprisingly tricky in some context In webapp, for example 17. 2010 CloudBees, Inc. All Rights Reserved 172010 CloudBees, Inc. All Rights Reserved #5: Turtles all the way down Extensibility needs to be recursive Extensions should define its own extension points In Jenkins, we provide an idiom Partly culture Partly refactoring 18. 2010 CloudBees, Inc. All Rights Reserved 182010 CloudBees, Inc. All Rights Reserved Symptom of fake modularity/extensibility Division of labor is not modularity Modules are tailor-fit to their neighbors Contracts arent general enough A fixed set of modules become the product Mosaic I - M.C. Escher 19. 2010 CloudBees, Inc. All Rights Reserved 192010 CloudBees, Inc. All Rights Reserved Extensibility in Jenkins Core Creates structure Includes Modules (plugins in disguise) 600+ Plugins Actually provide useful CI functionalities 20. 2010 CloudBees, Inc. All Rights Reserved 202010 CloudBees, Inc. All Rights Reserved The Question 21. 2010 CloudBees, Inc. All Rights Reserved 212010 CloudBees, Inc. All Rights Reserved http://www.flickr.com/photos/jvuokko/4566270758/ 22. 2010 CloudBees, Inc. All Rights Reserved 222010 CloudBees, Inc. All Rights Reserved Extensible silo is a good thing It forces contracts at boundaries Principles of continuous X: do it often enough and it becomes painless Small code is easier to hack Looking at 5 files feel easier than 500 files Faster to build, easier to maintain Special use case does not clutter general- purpose code/UI Example: Exclusion in Jenkins Subversion plugin Niche features are welcome 23. 2010 CloudBees, Inc. All Rights Reserved 232010 CloudBees, Inc. All Rights Reserved Extensible silo requires less communication Everyone gets his own sandbox to hack No need to discuss designs/features/schedules upfront No more conflicting development model Conference-driven development vs test- driven development No need to see someone elses ugly code No need to feel ashamed of it 24. 2010 CloudBees, Inc. All Rights Reserved 242010 CloudBees, Inc. All Rights Reserved Extensible silo fosters innovations Every whacky idea gets a shot No need to sell ideas No need to turn down ideas Communicate in code, not in English Some of them will turn out great No need to drag failed experiments 25. 2010 CloudBees, Inc. All Rights Reserved 252010 CloudBees, Inc. All Rights Reserved Extensibility highlights higher-order problems With enough silos, core devs become silo devs What core does directly benefits silos Simplified build mechanism IDE support Error checker for common mistakes It accelerates dev scalability 26. 2010 CloudBees, Inc. All Rights Reserved 262010 CloudBees, Inc. All Rights Reserved Lower barrier to entry, enabled by silo In Jenkins, everyone gets to be a committer Just ask, and itll be given We even have an IRC bot that does this This works, because People arent collaborating Any damage done is compartmentalized VCS enables rollback so long as its not released After all, unless you are Linus Torvalds, too many committers is not your problem 27. 2010 CloudBees, Inc. All Rights Reserved 272010 CloudBees, Inc. All Rights Reserved Lower barrier to entry: observations People are cautious when they have power Very few incidents Works well when people move on Abandoned plugins get new maintainers It encourages small contributions You can never predict who becomes significant contributors 28. 2010 CloudBees, Inc. All Rights Reserved 282010 CloudBees, Inc. All Rights Reserved But silo alone doesnt create a community Image: NASA/JPL-Caltech 29. 2010 CloudBees, Inc. All Rights Reserved 292010 CloudBees, Inc. All Rights Reserved You need a center of gravity Something that: Drag everything together Pulls in people Shared source tree repo doesnt have to be it Image: NASA/JPL-University of Arizona 30. 2010 CloudBees, Inc. All Rights Reserved 302010 CloudBees, Inc. All Rights Reserved Center of Gravity in Jenkins: IRC Closest thing to the water cooler in OSS It is a place people can come, unlike Twitter You can be present & absent at the same time It builds human relationships 31. 2010 CloudBees, Inc. All Rights Reserved 312010 CloudBees, Inc. All Rights Reserved Center of Gravity in Jenkins: outreach Connecting people Meet-ups, Hackathon, Events Giving the project a voice Twitter, Blog Mad props to @agentdero 32. 2010 CloudBees, Inc. All Rights Reserved 322010 CloudBees, Inc. All Rights Reserved But above all: Update Center UI built into Jenkins to let users install plugins To be listed, your plugins need to be co- located in GitHub org Commit access covers all the repos Everyone can add others to the project 33. 2010 CloudBees, Inc. All Rights Reserved 332010 CloudBees, Inc. All Rights Reserved Observations Creates an incentive for devs to come When people move on, Keeping plugin alive is easier A structure helps new contributors Right thing is now the easiest thing Providing pin-point technical help is easier 34. 2010 CloudBees, Inc. All Rights Reserved 342010 CloudBees, Inc. All Rights Reserved Center of Gravity = Self-reinforcing As we acquire more plugins We attract more users UC becomes more attractive to devs Machinery gets oiled As a result of solving higher-order problem 35. 2010 CloudBees, Inc. All Rights Reserved 352010 CloudBees, Inc. All Rights Reserved Emerging Challenges Subversion Git changed dynamics Repository no longer projects enough gravity GitHub and pull requests Its great that contributions are easier But it also creates throw the stuff over the wall mentality It lets people contribute without joining, reducing the inflow 36. 2010 CloudBees, Inc. All Rights Reserved 362010 CloudBees, Inc. All Rights Reserved Conclusions Scale development with extensibility Reduce communication with extensibility Let people innovate with extensibility I think I made Steve proud Extensibility! Extensibility! Extensibility! Extensibility! Extensibility! Extensibility! Extensibility! Extensibility! Extensibility! Extensibility! Extensibility! Extensibility!