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BitLogger/docs/api/runtime-sink-file-rotation-failures.md
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---
name: runtime-sink-file-rotation-failures
group: api
category: runtime
update-time: 20260613
description: Read the number of rotation failures recorded by a file-backed RuntimeSink.
key-word:
- runtime
- sink
- file
- public
---
## Runtime-sink-file-rotation-failures
Read the number of rotation failures recorded by a file-backed `RuntimeSink`. This helper is useful when direct runtime rotation behavior should be observed operationally.
### Interface
```moonbit
pub fn RuntimeSink::file_rotation_failures(self : RuntimeSink) -> Int {
```
#### input
- `self : RuntimeSink` - Runtime sink whose rotation-failure counter should be inspected.
#### output
- `Int` - Number of recorded rotation failures.
### Explanation
Detailed rules explaining key parameters and behaviors
- Plain `File` runtime variants report the wrapped `FileSink` rotation-failure count.
- `QueuedFile` runtime variants forward the metric from the wrapped inner `FileSink`.
- Non-file runtime variants return `0`.
- The counter is cumulative until `file_reset_failure_counters()` clears it.
### How to Use
Here are some specific examples provided.
#### When Need Rotation-specific Diagnostics
When support output should reveal whether rotation is failing:
```moonbit
let count = sink.file_rotation_failures()
```
In this example, the runtime sink exposes a focused metric for direct rotation-path health.
#### When Validate Runtime Rotation Tuning
When changed rotation settings should be checked in operation:
```moonbit
ignore(sink.file_rotation_failures())
```
In this example, callers can observe whether runtime rotation changes introduced problems.
### Error Case
e.g.:
- If the runtime sink is not file-backed, the method returns `0`.
- If callers need both rotation config and failure metrics, they should combine this helper with `file_rotation_config()` or `file_state()`.
### Notes
1. Use this helper when diagnosing direct runtime file rotation reliability.
2. It is especially relevant when runtime rotation policy can change after startup.