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BitLogger/docs/api/runtime-sink-dropped-count.md
2026-06-13 22:38:14 +08:00

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---
name: runtime-sink-dropped-count
group: api
category: runtime
update-time: 20260613
description: Read the cumulative dropped-record count from a RuntimeSink.
key-word:
- runtime
- sink
- queue
- public
---
## Runtime-sink-dropped-count
Read the cumulative dropped-record count from a `RuntimeSink`. This helper exposes the direct sink-level loss metric for queue-backed runtime variants.
### Interface
```moonbit
pub fn RuntimeSink::dropped_count(self : RuntimeSink) -> Int {
```
#### input
- `self : RuntimeSink` - Runtime sink whose dropped-record metric should be inspected.
#### output
- `Int` - Number of dropped records reported by the runtime sink.
### Explanation
Detailed rules explaining key parameters and behaviors
- Queue-wrapped runtime variants forward to the wrapped queue sink's `dropped_count()` value.
- Plain console and plain file runtime variants return `0` because they do not track queued record drops.
- The counter is cumulative for the lifetime of the concrete runtime sink value.
- This method is the direct sink-level API used by `ConfiguredLogger::dropped_count(...)`.
### How to Use
Here are some specific examples provided.
#### When Need Direct Queue Loss Visibility
When a runtime sink may discard records under pressure:
```moonbit
if sink.dropped_count() > 0 {
println("runtime sink dropped records")
}
```
In this example, direct runtime queue loss becomes visible without inspecting inner fields manually.
#### When Compare Queue Tuning Changes
When queue overflow behavior should be checked operationally:
```moonbit
ignore(sink.dropped_count())
```
In this example, the helper exposes the metric needed to compare different queue settings.
### Error Case
e.g.:
- If the runtime sink is not queue-backed, the method simply returns `0`.
- If callers need the higher-level logger wrapper API, use `ConfiguredLogger::dropped_count()` instead.
### Notes
1. This helper reports cumulative loss, not the reason for that loss.
2. Pair it with `pending_count()` and queue configuration when investigating pressure.