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Nanaloveyuki
76 lines
2.0 KiB
Markdown
76 lines
2.0 KiB
Markdown
---
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name: queued-sink-pending-count
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group: api
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category: sink
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update-time: 20260613
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description: Read the current queued-record count from a QueuedSink.
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key-word:
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- sink
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- queue
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- backlog
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- public
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---
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## Queued-sink-pending-count
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Read the current queued-record count from a `QueuedSink[S]`. This is the direct sink-level backlog metric for records that have been queued but not yet drained to the wrapped sink.
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### Interface
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```moonbit
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pub fn[S] QueuedSink::pending_count(self : QueuedSink[S]) -> Int {
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```
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#### input
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- `self : QueuedSink[S]` - Queued sink whose current pending backlog should be inspected.
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#### output
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- `Int` - Current number of queued records.
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### Explanation
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Detailed rules explaining key parameters and behaviors
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- The return value is `self.queue.length()` at the time of the call.
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- This is a point-in-time metric and may change immediately after it is read.
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- It reflects queued records that have not yet been drained or flushed to the wrapped sink.
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- This helper does not mutate the sink.
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### How to Use
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Here are some specific examples provided.
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#### When Need Direct Queue Backlog Visibility
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When code is working with a `QueuedSink` value directly and wants to inspect backlog pressure:
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```moonbit
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let pending = sink.pending_count()
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```
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In this example, callers can inspect the current queue size without draining it.
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#### When Verify Drain Progress
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When manual draining should be checked operationally:
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```moonbit
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ignore(sink.drain(max_items=8))
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ignore(sink.pending_count())
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```
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In this example, the metric helps verify whether a drain step reduced queued backlog.
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### Error Case
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e.g.:
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- This helper does not have a normal failure mode; it only reads current queue length.
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- If callers only need simple threshold buffering instead of an explicit queue, `BufferedSink::pending_count()` may be the better API.
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### Notes
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1. Use this helper for direct visibility into queue backlog on `QueuedSink` values.
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2. Pair it with `dropped_count()` when investigating queue pressure.
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