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BitLogger/docs/api/async-logger-has-failed.md
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2026-06-14 07:01:04 +08:00

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---
name: async-logger-has-failed
group: api
category: async
update-time: 20260614
description: Read whether the async logger worker has recorded a runtime failure after run() startup reset and drain execution.
key-word:
- async
- logger
- failure
- public
---
## Async-logger-has-failed
Read whether the async logger worker has encountered a failure. This helper is a compact health signal for async delivery problems.
### Interface
```moonbit
pub fn[S] AsyncLogger::has_failed(self : AsyncLogger[S]) -> Bool {}
```
#### input
- `self : AsyncLogger[S]` - Async logger whose failure flag should be inspected.
#### output
- `Bool` - Whether the worker has failed.
### Explanation
Detailed rules explaining key parameters and behaviors
- `run()` clears previous failure state at startup.
- `run()` also clears the stored `last_error()` string at startup before drain work begins.
- If the worker loop raises an error, the logger records that failure and exposes it through this flag.
- Once set by a failed run, the flag stays `true` until a later `run()` invocation actually starts and resets it.
- This helper is intentionally compact and should usually be paired with `last_error()` for details.
- Failure state is about runtime drain execution, not whether records were dropped due to overflow policy.
### How to Use
Here are some specific examples provided.
#### When Need A Fast Failure Signal
When runtime diagnostics should branch on worker health:
```moonbit
if logger.has_failed() {
println(logger.last_error())
}
```
In this example, the code checks failure state first, then reads the error detail.
#### When Inspect Async Runtime State In Tests
When a test needs to confirm that drain execution stayed healthy:
```moonbit
ignore(logger.has_failed())
```
In this example, the helper exposes a simple pass-fail runtime indicator.
### Error Case
e.g.:
- If `has_failed()` is `false`, queue pressure or dropped records may still exist for non-failure reasons.
- If `has_failed()` becomes `true`, `wait_idle()` may stop early while pending records still remain until a later close or clear path handles them.
- In the current regression coverage, that later handling can be an explicit `close(clear=true)` that resets pending backlog immediately or a runtime-dependent `shutdown(...)` path that either clears pending into dropped records or leaves the closed-queue remainder visible.
- If `has_failed()` is `true`, callers should inspect `last_error()` or `state()` for more context.
- `close()` or `shutdown()` do not clear this flag by themselves; only a later `run()` that has already started resets it.
### Notes
1. This helper reports worker failure, not general queue stress.
2. Pair it with `last_error()` when you need actionable detail.
3. Pair it with `is_running()` or `state()` when you also need to know whether the worker has already exited and whether backlog remains.