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feat: Allow Python Engine to end stream before final #2270

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Merged
merged 2 commits into from
Aug 5, 2025
Merged

feat: Allow Python Engine to end stream before final #2270

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be1a631
[WIP] Allow PyGeneratorExit to end stream without final flag
kthui Aug 2, 2025
0f41251
docs: Update backend.md on how to migrate ongoing requests
kthui Aug 5, 2025
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18 changes: 16 additions & 2 deletions lib/bindings/python/rust/engine.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -134,6 +134,9 @@ enum ResponseProcessingError {
#[error("python exception: {0}")]
PythonException(String),

#[error("python generator exit: {0}")]
PyGeneratorExit(String),

#[error("deserialize error: {0}")]
DeserializeError(String),

Expand Down Expand Up @@ -225,6 +228,9 @@ where
let msg = format!("critical error: invalid response object from python async generator; application-logic-mismatch: {}", e);
msg
}
ResponseProcessingError::PyGeneratorExit(_) => {
"Stream ended before generation completed".to_string()
}
ResponseProcessingError::PythonException(e) => {
let msg = format!("a python exception was caught while processing the async generator: {}", e);
msg
Expand Down Expand Up @@ -276,8 +282,16 @@ where
{
let item = item.map_err(|e| {
println!();
Python::with_gil(|py| e.display(py));
ResponseProcessingError::PythonException(e.to_string())
let mut is_py_generator_exit = false;
Python::with_gil(|py| {
e.display(py);
is_py_generator_exit = e.is_instance_of::<pyo3::exceptions::PyGeneratorExit>(py);
});
if is_py_generator_exit {
ResponseProcessingError::PyGeneratorExit(e.to_string())
} else {
ResponseProcessingError::PythonException(e.to_string())
}
})?;
let response = tokio::task::spawn_blocking(move || {
Python::with_gil(|py| depythonize::<Resp>(&item.into_bound(py)))
Expand Down
11 changes: 10 additions & 1 deletion lib/runtime/src/pipeline/network/ingress/push_handler.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
// limitations under the License.

use super::*;
use crate::protocols::maybe_error::MaybeError;
use prometheus::{Histogram, IntCounter, IntCounterVec, IntGauge};
use serde::{Deserialize, Serialize};
use std::sync::Arc;
Expand Down Expand Up @@ -105,7 +106,7 @@ impl WorkHandlerMetrics {
impl<T: Data, U: Data> PushWorkHandler for Ingress<SingleIn<T>, ManyOut<U>>
where
T: Data + for<'de> Deserialize<'de> + std::fmt::Debug,
U: Data + Serialize + std::fmt::Debug,
U: Data + Serialize + MaybeError + std::fmt::Debug,
{
fn add_metrics(&self, endpoint: &crate::component::Endpoint) -> Result<()> {
// Call the Ingress-specific add_metrics implementation
Expand Down Expand Up @@ -220,6 +221,14 @@ where
let mut send_complete_final = true;
while let Some(resp) = stream.next().await {
tracing::trace!("Sending response: {:?}", resp);
if let Some(err) = resp.err() {
const STREAM_ERR_MSG: &str = "Stream ended before generation completed";
if format!("{:?}", err) == STREAM_ERR_MSG {
tracing::warn!(STREAM_ERR_MSG);
send_complete_final = false;
break;
}
}
let resp_wrapper = NetworkStreamWrapper {
data: Some(resp),
complete_final: false,
Expand Down
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