Improve the build times of your project is not impossible. How we achieved it in N26.

In 2021/2022 N26 android platform team focused on reducing the build times of the project. We achieved to reduce them a 75%! This talk is about how we achieve that successful result that made the N26 Android Engineers happy and more productive.

I will present the implementations that N26 platform team did to reduce the compilation time of our app module from 20-25minuts to 5-6minuts. Also we reduced the compilation time of the library modules to improve the productivity of the engineers. I will talk about the gradle dependency graph, DI (Anvil plugin from square) and about the Dependency Inversion Principle.

Transcript

1. Antoni Castejón Improve the build times of your project is not impossible. How we achieved it in N26
2. Why?
3. STAKEHOLDERS 👨💻👩💻👨💻👩💻👨💻👩💻👨💻👩💻 👨💻👩💻👨💻👩💻👨💻👩💻👨💻👩💻 👨💻👩💻👨💻👩💻👨💻👩💻👨💻👩💻 👨💻👩💻👨💻👩💻👨💻👩💻👨💻👩💻 Android Team (Product) Mobile Core 👨💻👩💻 👨💻👩💻
4. 😭 ☹ 😶 🙂 🤩
6. It was highly demanded by our stakeholders
7. But… It was that painful to work with the project?
8. 24 minutes Full app build time (./gradlew clean app:assembleDebug) 🥲
9. The N26 android project
10. core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib single_feature_app 1 feature_app feature_lib single_feature_app 2 feature_app feature_lib single_feature_app 3 feature_app feature_lib single_feature_app 4 feature_app feature_lib The N26 android project Setup before the initiative app core libraries folder features folder
11. single_feature_app 1 feature_app feature_lib The N26 android project Single feature apps • The feature code • Runs independently • Entry point • Less dependencies • Less build time
12. feature_app The N26 android project Single feature apps • Login • Activity entry point • No production code • com.android.application
13. feature_lib The N26 android project Single feature apps • Feature code • Production code • com.android.library
14. The N26 android project Overview before the initiative • 312 total modules • 119 core libraries • 70 SFAs
15. How?
17. 🙅
18. 🤔
19. Then, what were the issues of the project impacting the build time? 🤔
20. • The Gradle dependency graph • Legacy monoliths
21. The Gradle dependency graph
22. Chat GPT 3.5 A visual representation of the dependencies between different components in a Gradle-based project. It refers to the relationships between different modules, libraries, and other dependencies that make up a gradle application. The Gradle dependency graph
23. https://github.com/jraska/modules-graph-assert
24. generateModulesGraphStatistics
25. Wikipedia - Glossary of graph theory (https://en.wikipedia.org/wiki/Glossary_of_graph_theory#height) The height of a node in a rooted tree is the number of edges in a longest path, going away from the root, that starts at that node and ends at a leaf.
26. Number of nodes, counting vertically, in the path from the root to the last one.
28. 20 The height of the app module
29. Hypothesis
30. Reducing the height of the graph the build time will be reduced
31. To flat the dependency graph
33. Height = 5
35. Height = 2
36. To reduce the height
37. Why?
38. Because of how Gradle build works
39. About Gradle Parallel execution
40. About Gradle Parallel execution 🔄 🔄 🔄 🔄 🔄 🔄 🔄 🔄 🔄 🔄 🔄 🔄 🔄
41. About Gradle Parallel execution 🔄 🔄 🔄 🔄 🔄 🔄 🔄 🔄
42. About Gradle Parallel execution 🔄 🔄 🔄 🔄
43. About Gradle Parallel execution 🔄 🔄 🔄
44. About Gradle Parallel execution 🔄
45. About Gradle Parallel execution 🔄
46. About Gradle Parallel execution
47. About Gradle Executing a gradle task… Current execution Previous execution Skips execution! Gradle incremental builds and caching Outputs Outputs
48. About Gradle Gradle incremental builds and caching Up-to-date checking
49. About Gradle But… Current execution Previous execution Reexecution is needed for those tasks Gradle incremental builds and caching Reexecution is NOT only needed for those tasks…
50. About Gradle Gradle incremental builds and caching Reexecution is NOT only needed for those tasks… … but also for the tasks that depend on them
51. About Gradle Gradle incremental builds and caching
52. About Gradle Gradle incremental builds and caching
53. About Gradle Gradle incremental builds and caching 🔄 🔄 🔄 🔄 🔄
54. About Gradle Gradle incremental builds and caching
55. About Gradle Gradle incremental builds and caching
56. About Gradle Gradle incremental builds and caching 🔄 🔄 🔄
57. Solution
58. Apply dependency inversion Solution proposed for the hypothesis • High-level modules should depend on abstractions rather than in low-level modules. • Abstractions should not depend on details. Details should depend on abstractions. SOLID D
59. Apply dependency inversion Solution proposed for the hypothesis public interface NetworkApi { fun connectToInternet() fun disconnectFromInternet() } Abstraction public class Network : NetworkApi { override fun connectToInternet() { // Starting connection... } override fun disconnectFromInternet() { // Disconnecting... } } Details
60. Apply dependency inversion Solution proposed for the hypothesis High-level modules should depend on abstractions rather than low- level modules. feature_lib details feature_lib abstraction
61. Apply dependency inversion Solution proposed for the hypothesis Abstractions should not depend on details. Details should depend on abstractions. feature_lib abstraction details feature_lib abstraction details
62. Apply dependency inversion Solution proposed for the hypothesis Abstraction and details module for every potential dependency
63. public class Network : NetworkApi { override fun connectToInternet() { // Starting connection... } override fun disconnectFromInternet() { // Disconnecting... } } public interface NetworkApi { fun connectToInternet() fun disconnectFromInternet() } Apply dependency inversion Solution proposed for the hypothesis abstraction details api core
64. Apply dependency inversion Solution proposed for the hypothesis core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib single_feature_app 1 feature_app feature_lib single_feature_app 2 feature_app feature_lib single_feature_app 3 feature_app feature_lib single_feature_app 4 feature_app feature_lib app core libraries folder features folder core_lib
65. Apply dependency inversion Solution proposed for the hypothesis core_lib api core
66. Before dependency inversion app feature_app feature_lib core_lib core_lib core_lib
67. feature_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib Before dependency inversion app feature_app feature_lib core_lib lib core_lib core_lib 😭
68. feature_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib Before dependency inversion core_lib
69. feature_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib Before dependency inversion core_lib 🔄 🔄 🔄 🔄 🔄 🔄 SEQUENTIALLY
70. With dependency inversion app feature_app feature_lib core_lib lib core_lib api api api api legacy app feature_app feature_lib core core 😃
71. With dependency inversion app feature_app feature_lib core_lib lib core_lib api api api api legacy app feature_app feature_lib core core 🔄
72. Proof of concept (POC) feature_ fl ag api core
73. 35% Build time reduced for a library module (from ~28 to ~18 sec)
74. 76% Edges count reduced (from 69 to 17)
75. 56% Height reduced (from 9 to 4)
78. What about a feature library?
79. 11% build time reduction for our feed library module
80. 1% for the app module
81. Process we follow Iterative Discovery Implementation Benchmark
82. Process we follow Iterative Discovery Pick the top 5 core libraries with: ✅ More edges ✅ Easy to apply Implementation Apply DI Benchmark Compare results: master changes
83. Legacy monoliths
84. Chat GPT 3.5 Monolith: A monolith refers to an application that is built as a single, unified unit. All components and features of the application are tightly integrated into a single codebase, often resulting in a large and complex code structure. Legacy monoliths
85. Large single module that does many different things Legacy monoliths
86. Chat GPT 3.5 Legacy: Refers to older software systems that are still in use but are no longer actively developed or maintained. These systems are usually built using older technologies, frameworks, and practices that might not align with modern software development trends and best practices. Legacy systems can pose challenges in terms of scalability, maintenance, and integration with newer technologies. Legacy monoliths
87. Old code Legacy monoliths
89. What was injectLegacy?
90. Anvil
91. https://github.com/square/anvil
92. Then, why not using Hilt?
93. Anvil VS Hilt Anvil • Kotlin compiler plugin • Needs Dagger • Merges components and modules using annotations • Doesn’t need Kapt Hilt • Dependency injection framework • Independent library • Simpli fi es Dagger DI for Android • Needs Kapt *
94. Anvil VS Hilt Anvil • Kotlin compiler plugin • Needs Dagger • Merges components and modules using annotations • Doesn’t need Kapt * ✅ Without @Component ✅ Pure Kotlin
95. How was Anvil applied in our project?
96. app feature_app feature_lib feature_lib core With Kapt No Kapt
97. Then, what was injectLegacy?
98. core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib injectLegacy injectLegacy BaseComponent BaseSessionComponent feature_lib core_lib Legacy monoliths app
99. What we did?
100. app Legacy monoliths injectLegacy core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib injectLegacy BaseComponent BaseSessionComponent feature_lib core_lib ✅ Removed injectLegacy dependency ✅ Add Anvil plugin (if necessary) Done by Platform team 1 ✅ Adds Anvil Plugin ✅ Removed injectLegacy dependency Done by Product teams 2
101. Involving product teams 1. Step by step guide 2. Tracked the process 3. Capacity of the teams 4. Explained the bene fi ts Explained the bene fi ts
102. Involving product teams Explained the bene fi ts ✅ Height of the SFA ✅ Skip Kapt The build time of their SFA library will be reduced :
103. Involving product teams Explained the bene fi ts ✅ Height of the SFA ✅ Skip Kapt The build time of the app will be ALSO reduced :
104. 😭 ☹ 😶 🙂 🤩
106. core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib core_lib injectLegacy BaseComponent BaseSessionComponent feature_lib core_lib Legacy monoliths injectLegacy ✅ Removed injectLegacy dependency ✅ Add Anvil plugin (if necessary) Done by Platform team 1 ✅ Adds Anvil Plugin ✅ Removed injectLegacy dependency Done by Product teams 2 ✅ Delete injectLegacy Done by Platform team 3
107. Legacy monoliths injectLegacy
108. Legacy monoliths injectLegacy 🔪💀
109. Results
110. 20 The height of the app module
111. 11 The height of the app module 20
112. 45% 🎉 The height of the app module
113. 24 minutes Full app build time (./gradlew clean app:assembleDebug)
114. 6 minutes Full app build time (./gradlew clean app:assembleDebug) 24 minutes
115. 75% 🎉 Full app build time (./gradlew clean app:assembleDebug)
116. Take-aways
117. 👀 Gradle dependency graph
118. 🔁 Iterate
119. 🕵 Discovery
120. 📈 Continuous monitoring
121. 📚 Documentation
122. 💪 Challenge the status quo
123. Thanks ❤ Antoni Castejón @antoni_castejon