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[adapters] Warn when the pipeline stalls due to output buffers filling. #5170

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Merged
blp merged 1 commit into from
Nov 25, 2025
Merged

[adapters] Warn when the pipeline stalls due to output buffers filling. #5170

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13 changes: 11 additions & 2 deletions crates/adapters/src/controller.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1806,6 +1806,7 @@ impl CircuitThread {
};
let _ = init_status_sender.send(Ok(self.controller.clone()));

let mut output_backpressure_warning = None;
loop {
// Run received commands. Commands can initiate checkpoint
// requests, so attempt to execute those afterward. Executing a
Expand All @@ -1828,10 +1829,18 @@ impl CircuitThread {
// become available.
if self.controller.output_buffers_full() {
debug!("circuit thread: park waiting for output buffer space");
self.parker.park();
debug!("circuit thread: unparked");
let warning = output_backpressure_warning
.get_or_insert_with(|| LongOperationWarning::new(Duration::from_secs(1)));
warning.check(|elapsed| {
info!(
"pipeline stalled {} seconds because output buffers are full",
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@lalithsuresh lalithsuresh Nov 24, 2025

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To make the error message more actionable, would it be possible to add some more user feedback like:

"pipeline stalled {} seconds because output buffers from connector {connector-name} are full (observed output throughput is {} records/second). Pleases tune the output connector or downstream data destination for higher throughputs."

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@blp blp Nov 24, 2025

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Yes, this is absolutely possible, and it would be a better message than what I added. But it would also take me the rest of the day to do, instead of an hour this morning. It's a compromise between insight and implementation time.

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@lalithsuresh lalithsuresh Nov 24, 2025

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Maybe merge this and add an issue (possibly even a meta issue) that collects instances like this.

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@blp blp Nov 25, 2025

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Maybe merge this and add an issue (possibly even a meta issue) that collects instances like this.

#5177

elapsed.as_secs()
)
});
self.parker.park_deadline(warning.next_warning());
continue;
}
output_backpressure_warning = None;

match trigger.trigger(
self.last_checkpoint,
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4 changes: 4 additions & 0 deletions crates/adapters/src/util.rs
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Expand Up @@ -708,6 +708,10 @@ impl LongOperationWarning {
self.warn_threshold *= 2;
}
}

pub fn next_warning(&self) -> Instant {
self.start + self.warn_threshold
}
}

#[cfg(test)]
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