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BitLogger/docs/api/configured-logger.md
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2026-06-14 01:23:15 +08:00

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---
name: configured-logger
group: api
category: runtime
update-time: 20260613
description: Public configured runtime logger alias used for config-built sync logging with queue and file controls.
key-word:
- logger
- runtime
- alias
- public
---
## Configured-logger
`ConfiguredLogger` is the public sync runtime logger type returned by config-driven build APIs. It is a direct alias to `Logger[RuntimeSink]`, so it keeps ordinary logger write methods while also exposing configured queue and file runtime helpers.
### Interface
```moonbit
pub type ConfiguredLogger = Logger[RuntimeSink]
```
#### output
- `ConfiguredLogger` - Public config-built runtime logger backed by `RuntimeSink`.
### Explanation
Detailed rules explaining key parameters and behaviors
- This is a type alias, not a separate wrapper implementation.
- It preserves normal logger methods such as `info(...)`, `warn(...)`, `error(...)`, and the other `Logger` APIs.
- It also exposes configured runtime helpers such as `flush()`, `drain()`, `pending_count()`, `dropped_count()`, and file-specific controls when the runtime sink supports them.
- Builders such as `build_logger(...)` and `parse_and_build_logger(...)` return this alias as the main sync config-to-runtime result.
- `ApplicationLogger` is another direct alias-oriented name for this same configured runtime surface, while `LibraryLogger[RuntimeSink]` is the narrowing facade variant that intentionally hides these runtime helpers until `to_logger()` is used.
### How to Use
Here are some specific examples provided.
#### When Need A Typed Config-built Runtime Logger
When boot code should keep the built logger as a named runtime type:
```moonbit
let logger : ConfiguredLogger = build_logger(LoggerConfig::new(target="svc"))
```
In this example, the configured runtime logger remains a first-class typed value after config assembly.
#### When Need Normal Logging Plus Runtime Controls
When code should both emit logs and inspect configured runtime behavior:
```moonbit
logger.info("started")
ignore(logger.pending_count())
```
In this example, the alias keeps ordinary logging calls while still exposing runtime diagnostics.
### Error Case
e.g.:
- `ConfiguredLogger` itself does not have a runtime failure mode.
- The concrete behavior of queue and file helpers still depends on the configured `RuntimeSink` shape and current backend support.
### Notes
1. Use `build_logger(...)` or `parse_and_build_logger(...)` when you need a value of this type.
2. Use `ApplicationLogger` when application code wants the same full configured-runtime helper surface under an app-facing name.
3. Use `LibraryLogger[RuntimeSink]` when a library boundary should intentionally hide configured-runtime helper methods behind a narrower facade.