📝 document runtime sink state surface

2026-07-26 09:52:31 +00:00 · 2026-06-13 22:38:14 +08:00
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+---
+name: runtime-sink
+group: api
+category: runtime
+update-time: 20260613
+description: Public runtime sink enum used by config-built synchronous loggers to unify console, file, and queued sink variants.
+key-word:
+    - runtime
+    - sink
+    - type
+    - public
+---
+
+## Runtime-sink
+
+`RuntimeSink` is the public runtime sink enum used by config-built synchronous loggers. It unifies console, file, and queued sink variants behind one runtime-facing sink surface.
+
+### Interface
+
+```moonbit
+pub(all) enum RuntimeSink {
+  Console(ConsoleSink)
+  JsonConsole(JsonConsoleSink)
+  TextConsole(FormattedConsoleSink)
+  File(FileSink)
+  QueuedConsole(QueuedSink[ConsoleSink])
+  QueuedJsonConsole(QueuedSink[JsonConsoleSink])
+  QueuedTextConsole(QueuedSink[FormattedConsoleSink])
+  QueuedFile(QueuedSink[FileSink])
+}
+```
+
+#### output
+
+- `RuntimeSink` - Public runtime sink union used by `ConfiguredLogger` and config-built logging helpers.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- This is a public enum root type, not a type alias.
+- The variants cover plain console sinks, plain file sinks, and queue-wrapped forms of those sink families.
+- `build_logger(...)` and related config-driven construction paths use this type as the concrete sink behind `ConfiguredLogger`.
+- The type exposes direct runtime helpers such as `flush()`, `drain()`, `close()`, `pending_count()`, and `dropped_count()`.
+- Queue-specific metrics are meaningful only for queued variants, while plain variants usually report `0` for queue counters.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need A Typed Config-built Runtime Sink Surface
+
+When code should keep the runtime sink union explicit after config assembly:
+```moonbit
+let logger = build_logger(LoggerConfig::new(target="svc"))
+let sink : RuntimeSink = logger.sink
+```
+
+In this example, the concrete runtime sink remains available for direct runtime inspection.
+
+#### When Need Direct Runtime Variant-specific Branching
+
+When behavior should differ between plain and queued runtime sink variants:
+```moonbit
+match sink {
+  QueuedFile(inner) => ignore(inner.pending_count())
+  File(inner) => ignore(inner.is_available())
+  _ => ()
+}
+```
+
+In this example, the enum shape makes runtime sink-specific handling explicit.
+
+### Error Case
+
+e.g.:
+- `RuntimeSink` itself does not have a runtime failure mode.
+
+- Actual file behavior, queue backlog, and close results still depend on the active variant and current backend state.
+
+### Notes
+
+1. `ConfiguredLogger` is the main higher-level alias that wraps `Logger[RuntimeSink]`.
+
+2. Use the direct `RuntimeSink` helpers when code owns the sink value itself instead of only the logger wrapper.