kotlin-coroutines

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name: kotlin-coroutines description: Coroutine usage guardrails for Kotlin backend reviewers license: MIT

Mission

• Preserve non-blocking performance characteristics by enforcing clear coroutine boundaries.
• Prevent thread pool exhaustion, deadlocks, and latency spikes caused by mixing blocking and suspend flows.

Red Flags

• Mixing blocking and suspending calls inside the same function without isolating the blocking work.
• Calling runBlocking anywhere other than top-level entrypoints (resources, main) or when explicitly bridging to blocking code with the correct dispatcher.
• Using async { ... }.await() immediately, or using async just to change dispatchers.
• Wiring AsyncResponse (Dropwizard) to wrap blocking DAO calls instead of true suspend flows.

Review Checklist

• Verify suspending chains remain suspend: bubble suspend up through managers/resources or wrap legacy blocking code with withContext(Dispatchers.IO).
• Ensure blocking functions stay blocking all the way up the call stack; prefer dedicated blocking helpers (e.g., getUserBlocking) rather than ad-hoc runBlocking.
• When bridging to suspend from non-suspend contexts, check the dispatcher passed to runBlocking matches the underlying workload (usually Dispatchers.IO).
• Confirm AsyncResponse is only applied to non-blocking suspend flows (Cosmos, service clients with await/executeAwait). Flag usages that simply wrap JDBI or other blocking calls.
• Look for nested coroutine builders. Replace async/await pairs used sequentially with direct calls; use concurrent async only when awaiting later.
• Ensure dispatcher changes use withContext, not async, and that blocking calls inside suspend functions are guarded with the appropriate context.

Tooling Tips

• Grep for runBlocking, .await(), executeSync, or AsyncResponse to inspect how coroutines and blocking APIs mix.
• Read affected managers/resources to trace whether suspend functions bubble correctly.
• Glob modules like *Manager.kt, *Resource.kt, and *Dao.kt when you need broader context about call chains.