R.I.P.
Two threads, one counter
–
“Both threads won. The counter lost.”
Death certificate
- Status
- 🪦 Buried
- Cause of death
- Race conditionTwo things happened in the wrong order. Only sometimes, and never with a debugger attached.
- Severity
- Critical
- Hours to kill
- 38 hours
- Killed by
- Jashanpreet
- Language
- Java
- Born
- 22 Apr 2025
- Fix merged
- 9 May 2025
- Buried
- 19 May 2025
- Component
- analytics
- Symptoms
- Under load, page-view counts came out lower than the real traffic.
- The fix
- Used an atomic increment instead of read, add, write.
Timeline
Every life of this bug, oldest first.
Born as “Two threads, one counter”22 Apr 2025
Fix merged9 May 2025
Buried19 May 2025