CI is an eternal topic in software engineering, it is still evolving for mobile. With an introduction to Docker, and a full-fledged Docker image for Android, this presentation will guide you through all facts about using Docker for Android CI - benefits, limitations, pitfalls, tweaks, and performance. Follow me, you can build your own Acme CI at zero cost. Last but not least, there are some other tips about how Docker could help your mobile engineering.

1. Android meets Docker
Jing Li
ROME - APRIL 13/14 2018

3. Founded in 2009
13 countries
&
70+ cities
~ 120K
drivers
~ 11M active
passengers
Hamburg
Barcelona
Berlin
600+ employees

4. Developer Story

5. Pain in the Admin
provision ∞ machines

6. Containerization vs Virtualization

7. Why Docker?
Resource Isolation
Supported OS
Boot / Stop Time
Size
Low Extreme
Linux
Seconds
MB
*
Minutes
GB

8. Where the problem comes
Infer - A tool to detect bugs in Java and ... code.
Infer (http://fbinfer.com/) by Facebook, Inc.
Update Android SDK in Docker container
☠ AUFS

9. Dockerfile Best Practices
" Single responsibility
○ use compose for orchestration
" Minimize the number of layers
○ layer = intermediate image, supports caching
" Size matters, use what you have
○ Install & un- by separated steps will ⇧ image size
" Readability

10. Different Approaches
" BTRFS storage driver
" One image per Android API level
" Mount SDK volume

11. Solution for SDK update
Mount SDK volume in container
minimal by Bakunetsu Kaito from the Noun Project, spring by Free Fair & Healthy from the Noun Project, Save by Rflor from the Noun Project, Share by Matteo Della Chiesa from the Noun Project

12. NFS
✅ In one place
❓ Performance
No concurrent writing

13. Benchmark

14. Performance Comparison
2 build types, 107 unit tests ( x2 = 214 ), 2 UI tests
./gradlew clean check :demo:connectedAndroidTest
On-premises Docker (w/ cached AndroidSDK) 6 mins 48.0 secs
Other online CI solutions (w/o optimization) > 10 mins

15. Android Devices
" ARM emulator
" x86 emulator (requires KVM)
" USB (needs privileged mode, ⛔ for macOS)
" Wifi
" Cloud solutions (e.g. Genymotion Cloud)

16. Emulator

17. VNC
Image size
" without VNC-server
○ 563 MB
" with VNC-server
○ 626 MB

18. Performance of 📱
2 UI tests
ARM emulator @🐳 2 mins 4.615 secs
x86 emulator @🐳 (on Linux Host) 23.497 secs
Genymotion 25.335 secs

19. Out Of Memory

20. Memory Matters
_JAVA_OPTIONS
-XX:+UnlockExperimentalVMOptions
-XX:+UseCGroupMemoryLimitForHeap
Exit Code 137 = 128 + 9 = SIGKILL = Killed 1 = SIGHUP = Hangup
Comment killed by the kernel OOM killer JVM terminates the program and exits
JVM is not container aware

21. " Set up env
○ /root/.ssh/environment
" Authorization
○ /root/.ssh/authorized_keys
SSH

22. Jenkins Env Var
" Global level
○ Configure System -> Global properties -> Environment variables
" Node level
○ Manage Nodes -> Configure Node -> Node Properties -> Environment variables
" Job level
○ Configure Job -> Build -> Build Step -> Execute shell
○ Plugin: Environment Injector -> Inject variables to the build process / as a build step

23. Can we get any better?
Gradle distribution

24. Gradle distributions mirror server
" From: gradle/wrapper/gradle-wrapper.properties
" To: ~/.gradle/wrapper/dists
" SSL certificate - needs to be trusted by Java keystore
" /etc/hosts

25. And better?
Gradle caches
○ Don’t waste time downloading dependencies
○ ~/.gradle/caches/
Compiling (https://xkcd.com/303/) by xkcd

26. Reveal machine-dependent problem
" Encoding problem
○ expected:<Hall[��]chen> but was:<Hall[ö]chen>
" Hard coded Timezone in test
○ expected:2099-12-31T00:00:00.0000+0200
but was: 2099-12-31T00:00:00.0000+0000
" File & Path
○ File#listFiles() -> File[] (sort order depends on OS)

27. What else for mobile
" Integration Test
○ Prod / Test server
■ unreliable network
■ complex setup
○ Docker
■ out of the box for mobile dev
" Something else
○ Serverless ( Kotlin, Swift ) - reuse 📱 code

28. Hiring
" 👍 Offices in Hamburg, Berlin, Barcelona and etc.
" 👍 Visa sponsor, offer ✈ 🏠
○ Android Developers
○ iOS Developers
○ SDET
○ Backend / Frontend / Data / * Engineers
https://de.mytaxi.com/jobs

29. Grazie
thyrlian
Docker Image:
https://github.com/thyrlian/AndroidSDK
thyrlian