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Nanaloveyuki
87 lines
3.4 KiB
Markdown
87 lines
3.4 KiB
Markdown
---
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name: async-logger-wait-idle
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group: api
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category: async
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update-time: 20260614
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description: Wait until the async logger backlog drains to zero or a worker failure interrupts normal progress, using the repo's direct async call style.
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key-word:
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- async
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- logger
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- queue
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- public
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---
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## Async-logger-wait-idle
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Wait until the async logger backlog drains to zero. This helper is useful when callers want to observe idle state without fully shutting down the logger.
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### Interface
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```moonbit
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pub async fn[S] AsyncLogger::wait_idle(self : AsyncLogger[S]) -> Unit {}
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```
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#### input
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- `self : AsyncLogger[S]` - Async logger whose backlog should be waited on.
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#### output
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- `Unit` - No return value. The method completes when the logger becomes idle or failure prevents normal progress.
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### Explanation
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Detailed rules explaining key parameters and behaviors
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- The helper keeps yielding while `pending_count() > 0`.
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- If `has_failed()` becomes `true`, waiting stops early instead of continuing to spin.
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- This API does not close the logger or stop the worker.
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- A return from `wait_idle()` therefore means either backlog reached `0` or failure interrupted normal drain progress.
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- `wait_idle()` does not clear retained failure state by itself, so if pending records remain after a worker failure, later `wait_idle()` calls also short-circuit until another path changes that state.
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- A later `run()` can make `wait_idle()` meaningful again for the retained backlog, but only after that new worker invocation has actually started and reset the stale failure flag.
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- If no worker is draining the queue and no failure flag is raised, `wait_idle()` can wait indefinitely.
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- It is narrower than `shutdown()` and is useful when the logger should continue to be used later.
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### How to Use
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Here are some specific examples provided.
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#### When Need A Drain Barrier Without Shutdown
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When code should wait for queued work to flush before continuing:
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```moonbit
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logger.wait_idle()
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```
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In this example, the caller waits for backlog drain but leaves the logger usable afterward.
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#### When Need Phase Boundaries In Tests
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When a test wants to ensure earlier async logs were processed:
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```moonbit
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logger.wait_idle()
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println("phase complete")
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```
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In this example, the wait acts as a barrier between test phases.
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### Error Case
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e.g.:
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- If the worker has failed, `wait_idle()` stops waiting even if pending records remain.
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- If the worker was never started, or if nothing is making pending records decrease, `wait_idle()` can block indefinitely.
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- If callers need backlog cleanup after a failure-short-circuit, they still need a later `close(clear=true)` or `shutdown(...)` path.
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- In the current direct coverage, `wait_idle()` can return with `pending_count() > 0` after a worker failure, and the later cleanup path may either clear that backlog explicitly or follow the runtime-dependent shutdown split documented on `shutdown(...)`.
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- If callers retry `wait_idle()` immediately after such a failure without restarting the worker or forcing cleanup first, the call can return again with the same retained pending backlog.
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### Notes
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1. Use this helper when you want a drain barrier without closing the logger.
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2. Prefer `shutdown()` when lifecycle completion matters more than continued reuse.
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3. Pair it with `pending_count()` or `state()` when you need to distinguish true idleness from an early stop caused by worker failure.
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