📝 补充runtime文档

docs/api/configured-logger-drain-progress.md

@@ -0,0 +1,79 @@
+---
+name: configured-logger-drain-progress
+group: api
+category: runtime
+update-time: 20260707
+description: Return a structured generic drain progress snapshot for a ConfiguredLogger through RuntimeSink without collapsing queue and plain-file fallback semantics into one Int.
+key-word:
+    - logger
+    - runtime
+    - drain
+    - public
+---
+
+## Configured-logger-drain-progress
+
+Return a structured generic drain progress snapshot for a `ConfiguredLogger`. This is the recommended configured runtime wrapper over `RuntimeSink::drain_progress(...)` when code wants truthful generic progress instead of the compatibility `Int` returned by `drain()`.
+
+### Interface
+
+```moonbit
+pub fn ConfiguredLogger::drain_progress(
+  self : ConfiguredLogger,
+  max_items~ : Int = -1,
+) -> RuntimeSinkProgress {}
+```
+
+#### input
+
+- `self : ConfiguredLogger` - Config-driven runtime logger whose generic drain progress should be observed.
+- `max_items : Int` - Optional upper bound on drained queued items. Negative values mean no explicit bound.
+
+#### output
+
+- `RuntimeSinkProgress` - Structured progress snapshot returned by the wrapped `RuntimeSink::drain_progress(...)` call.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- This helper delegates directly to `self.sink.drain_progress(max_items=max_items)`.
+- Queue-wrapped sinks report drained queued items through `queue_advanced_count`.
+- Plain file sinks report the generic fallback flush step through `file_flush_step_count`.
+- Plain console-style sinks return a zeroed snapshot.
+- This helper keeps configured-runtime drain behavior explicit without forcing callers to interpret one mixed `Int`.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need Recommended Bounded Generic Drain Progress On A Config-built Logger
+
+When queued config-built output should be advanced in chunks with explicit semantics:
+```moonbit
+let progress = logger.drain_progress(max_items=16)
+```
+
+In this example, queue advancement and plain-file fallback stay separated.
+
+#### When Need Full Manual Generic Drain Progress
+
+When config-built support code should empty runtime queue work while keeping shape information:
+```moonbit
+let progress = logger.drain_progress()
+```
+
+In this example, the structured result still tells whether the logger was queue-backed or plain file-backed.
+
+### Error Case
+
+e.g.:
+- If the configured runtime sink is not queue-backed, the snapshot may stay zeroed or use the plain-file fallback field.
+
+- If callers need file-specific success semantics after queue delivery, `file_flush()` is the better API.
+
+### Notes
+
+1. Prefer `drain_progress()` over `drain()` in new configured-runtime code.
+
+2. Use `pending_count()` together with this helper when remaining backlog should also be observed.