📝 document file sink lifecycle methods

2026-07-30 15:04:48 +00:00 · 2026-06-13 22:14:13 +08:00
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+---
+name: file-sink-available
+group: api
+category: sink
+update-time: 20260613
+description: Read whether a FileSink currently has an available underlying file handle.
+key-word:
+    - file
+    - sink
+    - available
+    - public
+---
+
+## File-sink-available
+
+Read whether a `FileSink` currently has an available underlying file handle. This helper is useful for runtime diagnostics and for deciding whether reopen or fallback behavior is needed.
+
+### Interface
+
+```moonbit
+pub fn FileSink::is_available(self : FileSink) -> Bool {
+```
+
+#### input
+
+- `self : FileSink` - File sink whose current availability should be inspected.
+
+#### output
+
+- `Bool` - Whether the sink currently holds an active file handle.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- This method reports whether `self.handle` is currently `Some(_)`.
+- A sink can become unavailable after open failure or after an explicit `close()`.
+- This helper does not mutate sink state.
+- It is the direct `FileSink` counterpart to configured-logger file availability checks.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need Direct Sink Health Checks
+
+When code works with a concrete file sink and should verify handle readiness:
+```moonbit
+if !sink.is_available() {
+  println("file sink unavailable")
+}
+```
+
+In this example, the caller can detect whether the sink currently has an active file handle.
+
+#### When Gate Recovery Or Reopen Logic
+
+When a reopen step should only run after loss of availability:
+```moonbit
+let ok = sink.is_available()
+```
+
+In this example, the boolean result can drive later recovery behavior.
+
+### Error Case
+
+e.g.:
+- If the sink failed to open initially, this method returns `false`.
+
+- If callers need failure counters or a richer state snapshot rather than a yes-or-no result, `state()` is the better API.
+
+### Notes
+
+1. Use this helper for lightweight file sink health checks.
+
+2. Pair it with `reopen(...)`, `state()`, or failure-counter APIs when diagnosing file sink problems.