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ITT 2015 - Simon Stewart - Building Android App...

ITT 2015 - Simon Stewart - Building Android Apps at Speed and Scale

Every two weeks Facebook releases a new version of their flagship Android application which is one of the most widely used apps in the world. The codebase is worked on by a large engineering team. In this talk, Simon Stewart covers some of the technologies and approaches that Facebook use to allow their engineers to work with confidence and speed on the codebase, while at the same time ensuring solid and timely releases.

Istanbul Tech Talks

April 27, 2015
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  1. Large Repos Are Slow ▪Lots of commits a day Pulls

    are slow Checkouts are slow ▪Years of history Clones are slow Requires lots of disk space
  2. Shallow Checkouts Clone just the latest version Work locally without

    complete history Need more history? Download on demand HEAD HEAD-1 HEAD-2 HEAD-3
  3. Sparse Checkouts Work on just the files you need Build

    system integrations knows how to check out more ~/fbsource ios/... common/... ~/fbsource/.hg
  4. Watchman OS independent filesystem change notification Integrates with mercurial File

    checking operations scale linearly with number of files changed
  5. Large Repos Are Fast 50 times faster than git 2000

    hg improvements Up to More than
  6. Buck ▪Next generation build system ▪Designed for modern hardware ▪SSD

    ▪Plentiful RAM ▪Many cores ▪Automatically parallelizes builds ▪And it's Open Source
  7. Build Files java_binary( name = 'example-binary', deps = [ ':example',

    ], ) java_library( name = 'example', srcs = glob(['*.java']), deps = [ '//third-party/guava:guava', ], visibility = [ '//javatests/...', ], ) Build file. Typically named BUCK
  8. Build Files java_binary( name = 'example-binary', deps = [ ':example',

    ], ) java_library( name = 'example', srcs = glob(['*.java']), deps = [ '//third-party/guava:guava', ], visibility = [ '//javatests/...', ], ) Build file. Typically named BUCK A build rule of type "java_binary"
  9. Build Files java_binary( name = 'example-binary', deps = [ ':example',

    ], ) java_library( name = 'example', srcs = glob(['*.java']), deps = [ '//third-party/guava:guava', ], visibility = [ '//javatests/...', ], ) Build file. Typically named BUCK A build rule of type "java_binary" A target defined in the same build file
  10. Build Files java_binary( name = 'example-binary', deps = [ ':example',

    ], ) java_library( name = 'example', srcs = glob(['*.java']), deps = [ '//third-party/guava:guava', ], visibility = [ '//javatests/...', ], ) Build file. Typically named BUCK A build rule of type "java_binary" A target defined in the same build file Build rule of type "java_library"
  11. Build Files java_binary( name = 'example-binary', deps = [ ':example',

    ], ) java_library( name = 'example', srcs = glob(['*.java']), deps = [ '//third-party/guava:guava', ], visibility = [ '//javatests/...', ], ) Build file. Typically named BUCK A build rule of type "java_binary" A target defined in the same build file A target defined in another build file Build rule of type "java_library"
  12. Build Files java_binary( name = 'example-binary', deps = [ ':example',

    ], ) java_library( name = 'example', srcs = glob(['*.java']), deps = [ '//third-party/guava:guava', ], visibility = [ '//javatests/...', ], ) Build file. Typically named BUCK A build rule of type "java_binary" A target defined in the same build file A target defined in another build file Build rule of type "java_library" All targets have visibility
  13. Target and Action Graph Target Graph: a naive representation of

    targets defined in build files. Action Graph: an optimized graph of actions to perform as the build
  14. Language-Aware Smarts public class Foo { private String someField; public

    void doSomething(int times) { System.out.println("Wow! " + times); } } Buck calculates the ABI, and keys rebuilds of dependencies off that Packaging rules that depend on this will always be re-run.
  15. Language-Aware Smarts public class Foo { private boolean theCakeIsALie =

    true; public void doSomething(int times) { System.out.println("Wow! " + times); } } Private field changed: ABI remains the same as before
  16. Language-Aware Smarts public class Foo { private boolean theCakeIsALie =

    true; public void doSomething(int num) { System.out.println("Wow! " + num); } } Parameter name changed: ABI remains the same as before.
  17. Language-Aware Smarts public class Foo { private boolean theCakeIsALie =

    true; public void doSomething(String num) { System.out.println("Wow! " + num); } } Parameter type changed: ABI changes too!
  18. Language-Aware Smarts public class Foo { private boolean theCakeIsALie =

    true; public void doSomething(String num) { System.err.println("Wow! " + num); } } Body of method changed: ABI remains the same.
  19. Pervasive Caching • Only 3% of each build is unique.

    • Local and distributed caches slash build times.
  20. Buck Smarts Build rule knows all of the inputs that

    can affect its output Changes to dx and proguard for faster compilation Java ABI smarts Android resource smarts Daemon to watch file changes
  21. Sandcastle Design Single Master Distributed Queue Master Worker Worker Worker

    Worker Worker Worker Worker Worker Worker Worker Distributed Queue
  22. Summary Tool OSS? Link! Buck Yes https://facebook.github.io/buck/ Mercurial Yes http://mercurial.selenic.com/

    Watchman Yes https://facebook.github.io/watchman/ hgwatchman Yes https://bitbucket.org/facebook/hgwatchman remote filelog Yes https://bitbucket.org/facebook/remotefilelog Sandcastle No