Async Jersey + Kotlin Coroutines
Article Summary
ClassPass engineers were hitting a wall: their Jersey-based APIs couldn't handle traffic spikes without exhausting thread pools. The culprit? Synchronous request processing blocking precious I/O threads.
Dan Murphy from ClassPass Engineering shares how they integrated Jersey's async API with Kotlin coroutines to build more resilient backend services. The team had to solve tricky challenges around connection leaks, logging context, and APM instrumentation.
Key Takeaways
- Async Jersey frees I/O threads immediately, preventing bottlenecks during long-running requests
- Built submitToCoroutine extension to avoid ceremony and prevent connection leaks
- Solved MDC logging context loss using kotlinx-coroutines-slf4j integration
- Custom dispatcher links New Relic transactions across coroutine thread switches
- Result: apps now handle traffic spikes and isolate high-latency endpoint impact
Critical Insight
Combining Jersey's async API with Kotlin coroutines made ClassPass services more resilient under load while maintaining observability.
