Open Source at Scale

1. Open Source at Scale
1
Garrett Moon
OSCON, July 23rd, 2015
Building Pinterest’s iOS App

2. Open Source at Scale
2
Garrett Moon
OSCON, July 23rd, 2015
Building Pinterest’s iOS App

3. 3
Dependencies
Shipping
Bugs
Images

4. 4
Dependencies
Shipping
Bugs
Images

5. Why We Use Open Source
5
Scale
Pinterest has significantly fewer iOS engineers than Facebook
1
Speed
Move quickly from prototype to production
2
Reliability
Open source projects are often old and well tested
3

7. Open Source At Pinterest
7
Over 15 open source projects
Pinball: A scalable workflow manager
Secor: A service implementing Kafka log persistence
PINCache: Fast non-deadlocking parallel object cache for iOS and OS X

8. Open Source on iOS
• AFNetworking
• PINCache
• PINRemoteImage
• FLAnimatedImage
• Kingpin
• Masonry
• AsyncDisplayKit
• Pop
• Realm
Just some of the great projects we use
8
2:50 PM 100%

9. 9
target 'PINRemoteImage', :exclusive => true do
pod "PINRemoteImage", :path => "../"
pod "PINCache", '2.0'
pod "libwebp"
end
target 'PINRemoteImage Tests', :exclusive => true
do
pod "PINRemoteImage", :path => "../"
end
Package Management
with CocoaPods
Specify version numbers.
Run `pod outdated` regularly.

10. 10
Dependencies
Shipping
Bugs
Images

11. No second
chances
Shipping iOS apps is like
shipping packaged
software.
11

12. Ship Frequently & Regularly
Monday Tuesday Wednesday Thursday Friday
START

13. Ship Frequently & Regularly
Monday Tuesday Wednesday Thursday Friday
START CODE
CODE CODE CODE CODE CODE
CODE FEATURE FREEZE > P2 BUGS > P2 BUGS CODE FREEZE
> P1 BUGS > P1 BUGS SUBMIT

14. Ship Frequently & Regularly
Monday Tuesday Wednesday Thursday Friday
START CODE
CODE CODE CODE CODE CODE
CODE FEATURE FREEZE > P2 BUGS > P2 BUGS CODE FREEZE
> P1 BUGS > P1 BUGS SUBMIT WAIT WAIT
WAIT WAIT WAIT SHIP

15. Ship Frequently & Regularly
Monday Tuesday Wednesday Thursday Friday
START CODE
CODE CODE CODE CODE CODE
CODE FEATURE FREEZE > P2 BUGS > P2 BUGS CODE FREEZE
> P1 BUGS > P1 BUGS SUBMIT START CODE
CODE CODE CODE SHIP CODE
CODE FEATURE FREEZE > P2 BUGS > P2 BUGS CODE FREEZE

16. Ship Frequently & Regularly
Monday Tuesday Wednesday Thursday Friday
> P1 BUGS > P1 BUGS SUBMIT START CODE
CODE CODE CODE CODE CODE
CODE FEATURE FREEZE > P2 BUGS > P2 BUGS CODE FREEZE
> P1 BUGS > P1 BUGS SUBMIT START CODE
CODE CODE CODE SHIP CODE
CODE FEATURE FREEZE > P2 BUGS > P2 BUGS CODE FREEZE

17. Ship Frequently & Regularly
Monday Tuesday Wednesday Thursday Friday
> P1 BUGS > P1 BUGS SUBMIT START CODE
CODE CODE CODE CODE CODE
CODE FEATURE FREEZE > P2 BUGS > P2 BUGS CODE FREEZE
> P1 BUGS > P1 BUGS SUBMIT START CODE
CODE CODE CODE SHIP CODE
CODE FEATURE FREEZE > P2 BUGS > P2 BUGS CODE FREEZE
P1 > BUGS P1 > BUGS SUBMIT START CODE
CODE CODE CODE SHIP CODE
CODE FEATURE FREEZE > P2 BUGS > P2 BUGS CODE FREEZE
> P1 BUGS > P1 BUGS SUBMIT

18. 18
Dependencies
Shipping
Bugs
Images

19. Crashes
Crash Reporting
• Helps diagnose and fix issues from previous
releases
• Users affected
• Sessions affected
• Devices affected
Tools
• NSZombies
• Leaks
• Address Sanitizer
19

20. 20
Testing
Continuous Testing
• Unit tests around processing code and
models
• Continuous Integration testing around
core library interactions
• UI Automation tests around core flows
User Testing
• Nightly internal builds for all employees
• Small contracted team does user testing
nightly
• Core team tests rigorously before release

21. Deadlocks
• Possibly stuck in a loop
• Probably blocked waiting on another thread
• Sometimes caused by a corrupted UI
• Thread explosion when using queues as
locks
• Dogfood with a deadlock detector
21

22. Thread explosion
The dark side of using a serial queue as a lock
22
Main Thread Serial Queue
Create a threadx100
waiting…
waiting…
Concurrent Queue

23. Deadlocks
• Possibly stuck in a loop
• Probably blocked waiting on another thread
• Sometimes caused by a corrupted UI
• Thread explosion when using queues as
locks
• Dogfood with a deadlock detector
23

24. Monitoring
• Log everything
• API requests
• Client side usage
• Performance
• Monitor to spot problems
• App Store ratings
• Crash rates
• Usage metrics
24

25. Experimenting
• Everything is an experiment
• Short and long term analyses
• You are the only one desperate for your new
feature
25

26. Automation
• OTA builds
• Unit, integration and UI tests
• Performance tests
• Linters
26

27. 27
Dependencies
Shipping
Bugs
Images

28. Pinterest mobile users download hundreds of images per day.

29. Introducing PINRemoteImage
29
A thread safe, performant, feature rich image fetcher

30. PINRemoteImage
• Image downloading (obviously)
• Image caching (on disk and in memory)
• De-duping image downloads
• Setting download and processing priority
• Prefetching images
• Image decompression off the main thread
A thread safe, performant, feature rich image fetcher
30

31. Multi-format Support
• JPEG
• Progressive decoding
• PNG
• WebP
• FLAnimatedImage
Supports downloading a variety of
formats:
31

32. 32
Animated GIFs
Supported by FLAnimatedImage
FLAnimatedImageView *animatedImageView = [[FLAnimatedImageView alloc] init];
[animatedImageView setImageFromURL:
[NSURL URLWithString:@"http://pinterest.com/flyingKitten.gif"]];

33. Progressive JPEG
With an attractive blur
33
A mother with her son
Dejan Muazer
Cats
1
A mother with her son
Dejan Muazer
Cats
2
A mother with her son
Dejan Muazer
Cats
3
A mother with her son
Dejan Muazer
Cats
4

34. 34
Progressive JPEG
With an attractive blur
UIImageView *imageView = [[UIImageView alloc] init];
[imageView setUpdateWithProgress:YES];
[imageView setImageFromURL:
[NSURL URLWithString:@"http://pinterest.com/progressiveKitten.jpg"]];

35. Adaptable Quality Downloading
Download varying quality images based on network conditions
Confidential 35Source: Placeholder Numbers
2:50 PM 100%
50 Kbps
2:50 PM 100%
100 Kbps
2:50 PM 100%
200 Kbps

36. Adaptive Quality Downloading
36
Download varying quality images based on network conditions
UIImageView *imageView = [[UIImageView alloc] init];
[imageView setImageFromURLs:
@[[NSURL URLWithString:@"http://pinterest.com/lowQualityKitten.webp"],
[NSURL URLWithString:@"http://pinterest.com/mediumQualityKitten.webp"],
[NSURL URLWithString:@"http://pinterest.com/highQualityKitten.webp"]]];
[[PINRemoteImageManager sharedImageManager] setShouldUpgradeLowQualityImages:YES completion:nil];

37. Image Processing
With an easy to write processing block
37

38. Image Processing
With an easy to write processing block
38
[self.imageView setImageFromURL:
[NSURL URLWithString:@"http://pinterest.com/kitten-image.jpg"]
processorKey:@"rounded" processor:^UIImage *(PINRemoteImageManagerResult *result, NSUInteger *cost)
{
UIGraphicsBeginImageContext(result.image.size);
//add rounded clip
[result.image drawInRect:drawRect];
UIImage *processedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return processedImage;
}];

39. How it works
39
Whiskers
Download Kitten 1
Round Kitten 1
Round Kitten 1
Download
Round Kitten 1
Round Kitten 1
Process
Round Kitten 2
Download
Round Kitten 2
Process
MEOW.
MEOW.
MEOW.

40. PINRemoteImage
40
https://github.com/Pinterest/PINRemoteImage
Available now:

41. 41
garrett@pinterest.com
pinterest.com/garrettlunar
@garrettmoon
https://github.com/Pinterest/PINRemoteImage