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BitLogger/docs/api/async-logger-trace.md
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2026-05-12 14:04:44 +08:00

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---
name: async-logger-trace
group: api
category: async
update-time: 20260512
description: Enqueue a trace-level record through the async logger using the lowest built-in severity shortcut.
key-word:
- async
- logger
- trace
- public
---
## Async-logger-trace
Enqueue a trace-level record through the async logger. This is the convenience wrapper for `log(Level::Trace, ...)`.
### Interface
```moonbit
pub async fn[S] AsyncLogger::trace(
self : AsyncLogger[S],
message : String,
fields~ : Array[@bitlogger.Field] = [],
) -> Unit {}
```
#### input
- `self : AsyncLogger[S]` - Async logger that should receive the trace record.
- `message : String` - Trace message text.
- `fields : Array[Field]` - Optional structured fields added to the record.
#### output
- `Unit` - No return value. The record is handled according to logger state and policy.
### Explanation
Detailed rules explaining key parameters and behaviors
- This helper delegates to `log(Level::Trace, ...)`.
- The record is still subject to min-level gating, patching, filtering, and overflow policy.
- Trace records are often skipped in production because they are the lowest built-in severity.
- Use this helper when explicit trace intent is clearer than a raw `log(...)` call.
### How to Use
Here are some specific examples provided.
#### When Need Fine-grained Async Diagnostics
When low-level execution flow should be observable during debugging:
```moonbit
await logger.trace("entered reconciliation step")
```
In this example, the call site makes trace intent explicit.
#### When Attach Structured Trace Data
When a trace event should carry extra fields:
```moonbit
await logger.trace(
"cache probe",
fields=[@bitlogger.field("key", "user:42")],
)
```
In this example, the record stays lightweight while still carrying structured detail.
### Error Case
e.g.:
- If the logger minimum level is above `Trace`, the record is skipped before enqueue.
- If the logger is closed or overflow policy prevents acceptance, the write may not become a normal queued record.
### Notes
1. Prefer this helper when trace intent is more readable than `log(Level::Trace, ...)`.
2. Trace-level async logging can increase queue pressure quickly under verbose workloads.