Working effectively at scale

Presented at BA:Swiftable in November, 2019.

1. Working e!ectively at scale
2. Francisco Díaz franciscodiaz.cl - @fco_diaz
3. Startups 2011 - 2017
4. Airbnb 2017 - today
14. organizations ... are constrained to produce designs which are copies of the communication structures of these organizations — Conway's law
15. How do you divide your codebase?
16. Architectural layer
17. User Flow
18. What about Airbnb?
20. 1 million lines of Swift
21. ~80 commits to master on any given day to the repo (Android + iOS)
22. Bigger buckets
24. A user should be able to wishlist a listing from the booking flow
25. How do they relate with each other?
29. 50 min local clean builds
30. ~30 min !
31. Buck HTTP Cache https://github.com/airbnb/BuckSample
33. ~5 min !
36. Dependency inversion
37. ‣High-level modules should not depend on low- level modules. Both should depend on abstractions. ‣Abstractions should not depend on details. Details (concrete implementations) should depend on abstractions.
39. A user should be able to wishlist a listing from the booking flow
41. Easy! WishListDataSource + interface!
43. WishListDataSource is still visible
45. Socializing best practices
46. !
47. +60 iOS developers
48. Automating best practices
49. Groups Modules
50. Groups Modules Module Types
51. Module Types Feature + Interface Service + Interface
52. Feature A screen or a flow in the app
53. Service Manage shared state or resources
56. How do we enforce these best practices?
57. /services /service_interfaces /features /feature_interfaces
58. def service_interface( name, deps): max_visibility = [ "//ios/feature_interfaces/...", "//ios/features/...", "//ios/service_interfaces/...", "//ios/services/...", ]
59. service_interface( name = "Networking", deps = [ "//ios/service_interfaces/Logging", ], )
60. feature( name = "Booking", deps = [ "//ios/service_interfaces/Networking", "//ios/service_interfaces/WishListService", ], )
61. iOS Platform
62. Module creation needs to be easy
65. rake make:module
66. > Provide the type of module you want to create: 1: Non Platform 2: Feature 3: Feature Interface 4: Service 5: Service Interface 4 > New module name: Swiftable > Provide a high level description of this module: This is a module to present at Swiftable
67. Buck Human readable dependencies https://github.com/airbnb/BuckSample
68. feature( name = "Booking", deps = [ "//ios/service_interfaces/Networking", "//ios/service_interfaces/WishListService", "//ios/feature_interfaces/HelpCenter", ], )
70. Feature A screen or a flow in the app
74. Dev Apps
75. ~1 min Dev Apps
76. Big buckets Small playgrounds
78. How do we get there?
79. ~100 modules One module type: /libraries
80. libraries/AirbnbBooking libraries/AirbnbBusinessTravel libraries/AirbnbHelpCenter libraries/AirbnbListings libraries/AirbnbNetworking libraries/AirbnbWishLists ...
81. Before iOS Platform /libraries
82. On the iOS Platform /services /service_interfaces /features /feature_interfaces
83. How to get everybody on the iOS Platform?
84. Remove libraries/ and start over
85. !
86. Progressively migrate
87. Let's migrate WishLists Data Source
88. libraries/WishLists
92. What are the dependency rules for libraries/?
94. Inbound dependencies Outbound dependencies
95. Inbound dependencies Outbound dependencies
97. The interface module has stricter rules
98. Migrate all the call sites
99. As the owner of WishLists We don't control these
101. Calculated tech debt
102. Inbound dependencies Outbound dependencies
104. we know our usage of Networking
105. We control our dependencies
106. Allow inbound dependencies from libraries/ Don't allow outbound dependencies to libraries/
107. libraries/ has access to the iOS Platform
108. The iOS Platform doesn't have access to libraries/
109. Code on the iOS Platform has good boundaries
110. while we allow for easier migration
111. def service_interface( name, visibility = []): max_visibility = [ "//ios/feature_interfaces/...", "//ios/features/...", "//ios/service_interfaces/...", "//ios/services/...", ] add_visibility_for_legacy_module_structure(max_visibility)
112. def add_visibility_for_legacy_module_structure(visibility): visibility.extend([ "//ios/libraries/...", ])
113. We started migrating from the bottom up
114. Try it ourselves !rst
115. Pilot with others teams
116. Should I implement this?
117. Most likely NO
118. There's no silver bullet
119. Adapt
120. Summary 1. Figure out where you're struggling 2.Create and document best practices 3.Automate best practices where needed
121. ¡Gracias! franciscodiaz.cl/talks