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Nanaloveyuki
80 lines
2.2 KiB
Markdown
80 lines
2.2 KiB
Markdown
---
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name: runtime-sink-file-state-or-none
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group: api
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category: runtime
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update-time: 20260707
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description: Read the current file sink snapshot from a RuntimeSink only when it is actually file-backed.
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key-word:
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- runtime
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- sink
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- file
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- truthful
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---
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## Runtime-sink-file-state-or-none
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Read the current file sink snapshot from a `RuntimeSink` only when it is actually file-backed.
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This is the truthful companion to `file_state()`. Prefer it when diagnostics or recovery logic must not confuse fallback snapshots with real file state.
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### Interface
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```moonbit
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pub fn RuntimeSink::file_state_or_none(self : RuntimeSink) -> FileSinkState? {
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```
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#### input
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- `self : RuntimeSink` - Runtime sink whose file state snapshot should be inspected.
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#### output
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- `FileSinkState?` - `Some(snapshot)` when the runtime sink is file-backed, otherwise `None`.
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### Explanation
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Detailed rules explaining key parameters and behaviors
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- Plain `File` runtime variants return `Some(live_snapshot)`.
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- `QueuedFile` runtime variants forward the wrapped inner file sink snapshot as `Some(live_snapshot)`.
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- Non-file runtime variants return `None`.
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- This helper is broader than individual counters or policy reads because it returns the aggregated file snapshot without fallback synthesis.
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### How to Use
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Here are some specific examples provided.
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#### When Need Truthful File Health Diagnostics
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When support output should include file state only for real file-backed sinks:
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```moonbit
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match sink.file_state_or_none() {
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Some(state) => println(stringify_file_sink_state(state, pretty=true))
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None => ()
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}
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```
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In this example, no compatibility snapshot is fabricated for non-file sinks.
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#### When Need State Without Queue Expansion
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When code only needs the file snapshot and not queue metadata:
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```moonbit
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let maybe_state = sink.file_state_or_none()
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```
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In this example, `None` cleanly signals missing file semantics.
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### Error Case
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e.g.:
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- If the runtime sink is not file-backed, the method returns `None`.
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- If callers also need queue metrics for queued file sinks, prefer `file_runtime_state()`.
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### Notes
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1. Prefer this helper over `file_state()` for truthful runtime diagnostics.
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2. `file_state()` remains available as the compatibility fallback API.
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