The New Gold Standard for iOS Releases: 99.99% Crash-Free
Article Summary
Turo's iOS team took their crash-free rate from 99% to 99.99% in just one year. Here's how a lean 5-engineer team achieved what most would consider impossible.
Eric Coffey Woods from Turo Engineering shares the journey of dramatically improving iOS app stability. The article breaks down their systematic approach to crash prevention, from code review practices to debugging mysterious Apple framework issues.
Key Takeaways
- Achieved >99.9% crash-free sessions and >99.95% crash-free users
- Used Xcode Memory Graph to find NSBlockOperation retain cycles causing crashes
- Phased releases let them catch issues before reaching all users
- Fixed mysterious UIFeedbackGenerator crash affecting only pre-iOS 12 devices
- Leveraged WWDC engineering hours to debug CoreGraphics memory corruption
Turo increased their iOS crash-free rate to 99.99% through rigorous code review, smart monitoring with phased releases, and deep debugging with Xcode's visual tools.
About This Article
Turo's iOS team found their biggest crash was ERROR_CGDataProvider_BufferIsNotReadable in CoreGraphics. The stack trace had no Turo code, so it looked like an Apple framework issue.
Eric Coffey Woods and colleagues went to WWDC engineering hours. Apple's CoreGraphics team told them the real problem was memory corruption from leaks elsewhere. They used Xcode's Memory Graph tool to find and fix NSBlockOperation retain cycles.
After fixing the retain cycle by changing strong references to weak references, thousands of crashes went away. Turo pushed their crash-free rate past their 99.9% target.