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BitLogger/docs/api/parse-async-logger-config-text.md
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---
name: parse-async-logger-config-text
group: api
category: async
update-time: 20260614
description: Parse JSON text into an AsyncLoggerConfig, applying async config defaults and accepted policy aliases.
key-word:
- async
- config
- parse
- public
---
## Parse-async-logger-config-text
Parse raw JSON text into `AsyncLoggerConfig`. This helper is the text-entry counterpart to `AsyncLoggerConfig::new(...)` when async queue and flush policy should be configured from serialized data.
### Interface
```moonbit
pub fn parse_async_logger_config_text(input : String) -> AsyncLoggerConfig raise {
```
#### input
- `input : String` - Raw JSON text describing async queue, batching, linger, and flush settings.
#### output
- `AsyncLoggerConfig` - Parsed async runtime config value.
### Explanation
Detailed rules explaining key parameters and behaviors
- This helper parses only the async config portion, not the embedded sync `LoggerConfig`.
- Missing `max_pending`, `overflow`, `max_batch`, `linger_ms`, and `flush` fields fall back to the same defaults used by `AsyncLoggerConfig::new(...)`.
- Parsed values then flow through `AsyncLoggerConfig::new(...)`, so `max_batch` and `linger_ms` receive the same constructor normalization.
- Overflow parsing accepts both `DropNewest` and the compatibility alias `DropLatest`.
- Flush parsing accepts both `Never` and the compatibility alias `None`.
- Use this API when async policy comes from config text but sink choice is still assembled elsewhere.
### How to Use
Here are some specific examples provided.
#### When Need Async Queue Policy From JSON
When async queue behavior is loaded separately from sync sink config:
```moonbit
let config = parse_async_logger_config_text(
"{\"max_pending\":8,\"overflow\":\"DropOldest\",\"max_batch\":3,\"linger_ms\":25,\"flush\":\"Batch\"}",
)
```
In this example, async queue and flush policy are parsed from text into a typed config object.
#### When Need Alias-friendly Async Policy Parsing
When external config may use compatibility labels:
```moonbit
let config = parse_async_logger_config_text(
"{\"overflow\":\"DropLatest\",\"flush\":\"None\"}",
)
```
In this example, parser aliases are accepted and normalized into the public enum values.
### Error Case
e.g.:
- If the JSON text is malformed, parsing raises an error.
- If enum names such as `overflow` or `flush` are unsupported, parsing raises an error.
- If a field is present with the wrong JSON type, parsing raises an error instead of silently coercing it.
### Notes
1. Use this helper when only async policy is text-driven.
2. Use `parse_async_logger_build_config_text(...)` when both sync logger config and async config come from the same JSON payload.
3. Omitted fields fall back to the default async config values rather than causing a missing-field error.