Lessons from Contributng to WebKit and Blink Bruno de Oliveira - - PowerPoint PPT Presentation

Lessons from Contributng to WebKit and Blink

Bruno de Oliveira Abinader WebKit, Chromium/Blink commiter abinader.com.br brunoabinader@gmail.com abinader @ irc.freenode.org

Contents

➢ Briefng on WebKit and Blink ➢ The WebKit development process ➢ The Blink development process ➢ Comparisons against Linux Kernel development process ➢ Final thoughts

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Briefng on WebKit

➢ Web engine: Used by apps to render web content ➢ Open source: Both BSD and LGPL licenses ➢ Community-oriented: Apple, Google, Intel, Samsung... ➢ Multple targets: Desktop, Mobile, Tablets ➢ Multple ports: Cocoa, Qt, EFL, GTK, OpenGL, Cairo

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WebKit: Project Statstcs

➢ Started in 2001 (fork of KHTML) ➢ Open sourced in 2005 ➢ 4.8 million LOCs (C++, C, Objectve-C) ➢ ~300 commiters, ~130 reviewers ➢ ~40% of browsers market share (Nov '12)

➢ Afer Blink: ~8.5% (Safari), ~40% (Chrome) (Sep '13)

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WebKit: Lines of Code

WebKit is open sourced Blink is forked 5 / 25

WebKit: Commits / Month

Blink is forked All time 12 months 30 days Commits 140887 23635 1545 Contributors 497 303 86 6 / 25

WebKit: Actve Contributors

7 / 25 Blink is forked Top 10 contributors Apple Google Nokia Research in Motion Igalia Intel Samsung

• Univ. Szeged

Adobe Torchmobile

Briefng on Blink

➢ Fork of WebKit as of April 2013 ➢ Single port: Chromium

➢ Not standalone: Chromium's content layer implementaton

➢ JavaScript engine: V8 (WebKit uses JavaScriptCore) ➢ Multprocess architecture: Browser + Renderer processes

➢ Difers from WebKit2 API multprocess architecture

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Blink: Diferent Goals

➢ Greater freedom in implementng WebCore's features

➢ Experimental features can be enabled on runtme

➢ Avoid vendor prefxes:

➢ No more -{moz,webkit,opera}-<property> polyflls!

➢ Lighter codebase:

➢ Cleaned inherited build systems, platorm and port-specifc code ➢ Move non-core layout and rendering code to Chromium

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Blink: Lines of Code

March 2013

(cleanup starts)

April 2013

(Blink is forked)

LOCs gets stabilized: ~2.5 MLOCs 10 / 25

Can commit patches Can follow bugs / trigger try bots

Hierarchical Map

Directory hierarchy Areas of knowledge

Reviewer (WebKit) Owner (Blink) Commiter Contributor*

Status Amount of people 11 / 25

WebKit: Submitng patches

Bugzilla

• 1. Create / Select a bug
• 2. Create patch / build / test
• 3. Upload patch
• 4. Early warning system
• 5. Request review fag (R?)
• 6. Request commit queue fag (CQ?)
• 7. Patch is landed

Gardening patch Manual commit 12 / 25

WebKit: Becoming a commiter

➢ Have around 25 reviewed patches landed ➢ Good judgement and understanding of project policies ➢ Good collaboraton skills ➢ Nominaton requires support of at least 3 reviewers:

➢ 1 to nominate, 2 to acknowledge ➢ Process happens inside reviewers-only mailing list

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WebKit: Becoming a reviewer

➢ Have around 100 reviewed patches landed ➢ Serious understanding of the source code

➢ Had informally reviewed other patches already ➢ Ensure reviewed patches follows project policies

➢ Exceptonal judgement on source code changes

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WebKit: Newcomer tps

*For more memes, go to webkitmemes.tumblr.com :-) 15 / 25

Blink: Submitng patches

Chromium issues

• 1. Create / Select a bug
• 2. Create patch / build / test
• 3. Upload patch
• 4. Try bots
• 5. Request review (LGTM?)
• 6. Trigger commit queue bot
• 7. Patch is landed

Codereview

Retries 3x Manual commit Bug gets notfed 16 / 25

Blink: Gaining status

➢ Commiter:

➢ Follows the same criteria as WebKit ➢ Can be speed up if already a WebKit commiter

➢ Owner:

➢ Have provided high quality reviews / design feedback ➢ Be a Chromium project member for at least 6 months ➢ Have submited a substantal number of non-trivial changes ➢ Had commited patches to the afected directory within 90 days ➢ Bandwidth to contribute with other owners

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Linux Kernel: Development Process

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➢ Vanilla releases made by Linus Torvalds

➢ Stable and Experimental releases also available ➢ New releases every 2-3 months ➢ WebKit / Blink: Version depends on target browser ➢ Patch lifetme: Quick for minor fxes, years for large and/or

controversial changes

➢ WebKit / Blink: Faster triaging tmes

Linux Kernel: Process stages

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• 1. Design
• 1. Design
• 2. Early review
• 2. Early review
• 3. Wider review
• 3. Wider review
• 4. Merging into

mainline

• 4. Merging into

mainline

• 5. Release
• 5. Release

Ofen done without involving community Patch gets posted to relevant mailing list Patch gets accepted by a subsystem maintainer Merging usually done by Linus Torvalds Developer should take responsibility for the code

Linux Kernel: Comparisons

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➢ Design step:

➢ WebKit and Blink promotes openness on current development ➢ i.e. “Intend to implement/ship” emails on Blink-dev ➢ Early review: ➢ WebKit uses bugzilla, Blink uses Rietveld (codereview) ➢ Good to track history / separate issues in a logical scope ➢ Plus: WebKit's Early Warning System, Blink's try bots

Linux Kernel: Comparisons

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➢ Wider review / merging into mainline:

➢ A reviewer/owner acknowledgement usually is enough ➢ In the worst case, patches can be rolled back ➢ Integraton: EWS/Try bots always have HEAD

➢ If the patch fails, developer takes responsibility to rebase / update ➢ Testng on the fy: Layout tests as replacement for unit tests

Linux Kernel: Comparisons

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➢ Hierarchy model:

➢ Developer → {driver, sub} maintainer→ subsystem maintainer

→ Linus Torvalds

➢ Developer → Andrew Morton → Linus Torvalds ➢ If a patch touches 2+ places maintained by 2+ maintainers,

“Acked-by” enters in scene

➢ Getng patches inside depends on fnding the right maintainer ➢ Remember WebKit meme on having a bad tme? :-)

Final thoughts

➢ WebKit, Blink and Linux Kernel projects are:

➢ Open source, community-oriented projects ➢ Strict in terms of development processes ➢ Meritocracy-based hierarchy levels ➢ WebKit and Blink awesomeness: ➢ Automatzed patch triage system (including tests) ➢ Bug tracking system / history (web tools)

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Questons? :-)

Thank you.

References:

• hloh.net – charts, statstcs

linuxfoundaton.org – Linux Kernel development steps webkit.org | chromium.org/blink – general informaton bitergia.com – top contributng companies Decks available in slideshare.net/brunoabinader abinader.com.br brunoabinader@gmail.com abinader @ irc.freenode.org