29 lines
2.1 KiB
Markdown
29 lines
2.1 KiB
Markdown
---
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name: kotlin-coroutines
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description: Coroutine usage guardrails for Kotlin backend reviewers
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license: MIT
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---
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## Mission
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- Preserve non-blocking performance characteristics by enforcing clear coroutine boundaries.
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- Prevent thread pool exhaustion, deadlocks, and latency spikes caused by mixing blocking and suspend flows.
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## Red Flags
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- Mixing blocking and suspending calls inside the same function without isolating the blocking work.
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- Calling `runBlocking` anywhere other than top-level entrypoints (resources, `main`) or when explicitly bridging to blocking code with the correct dispatcher.
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- Using `async { ... }.await()` immediately, or using `async` just to change dispatchers.
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- Wiring `AsyncResponse` (Dropwizard) to wrap blocking DAO calls instead of true suspend flows.
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## Review Checklist
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- Verify suspending chains remain suspend: bubble `suspend` up through managers/resources or wrap legacy blocking code with `withContext(Dispatchers.IO)`.
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- Ensure blocking functions stay blocking all the way up the call stack; prefer dedicated blocking helpers (e.g., `getUserBlocking`) rather than ad-hoc `runBlocking`.
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- When bridging to suspend from non-suspend contexts, check the dispatcher passed to `runBlocking` matches the underlying workload (usually `Dispatchers.IO`).
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- 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.
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- Look for nested coroutine builders. Replace `async/await` pairs used sequentially with direct calls; use concurrent `async` only when awaiting later.
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- Ensure dispatcher changes use `withContext`, not `async`, and that blocking calls inside suspend functions are guarded with the appropriate context.
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## Tooling Tips
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- `Grep` for `runBlocking`, `.await()`, `executeSync`, or `AsyncResponse` to inspect how coroutines and blocking APIs mix.
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- `Read` affected managers/resources to trace whether suspend functions bubble correctly.
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- `Glob` modules like `*Manager.kt`, `*Resource.kt`, and `*Dao.kt` when you need broader context about call chains.
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