charlesdong1991 commented on code in PR #555:
URL: https://github.com/apache/fluss-rust/pull/555#discussion_r3299471764
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crates/fluss/src/client/table/scanner.rs:
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@@ -378,6 +436,51 @@ impl LogScannerInner {
}
}
+ /// Records the start of a `poll()` call and emits
+ /// `SCANNER_TIME_BETWEEN_POLL_MS`. The first poll emits `0.0`,
+ /// matching Java's `ScannerMetricGroup.recordPollStart`
+ /// (`timeMsBetweenPoll = lastPollMs != 0L ? pollStartMs - lastPollMs :
0L`).
+ ///
+ /// In debug builds, panics if a previous poll has not yet recorded
+ /// its end — that indicates a concurrent `poll()` on the same scanner,
+ /// which violates the single-consumer contract (Java enforces this
+ /// with `LogScannerImpl.acquire()` and throws
+ /// `ConcurrentModificationException`).
+ fn record_poll_start(&self) {
+ let now = Instant::now();
+ let mut state = self.poll_state.lock();
+ debug_assert!(
+ state.poll_start_at.is_none(),
+ "concurrent poll() detected on the same scanner; \
+ LogScanner / RecordBatchLogScanner are single-consumer \
+ (see LogScannerImpl.acquire() for Java parity)"
+ );
+ let between_ms = match state.last_poll_at {
+ Some(prev) => now.duration_since(prev).as_secs_f64() * 1000.0,
+ None => 0.0,
+ };
+ state.time_between_poll_ms = between_ms;
+ metrics::gauge!(SCANNER_TIME_BETWEEN_POLL_MS).set(between_ms);
Review Comment:
sure! 👍
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