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feat: warn when requests get cancelled (#4064)

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Add a simple disarmable dropguard to log if request is cancelled before
it is completed. We currently don't have this, and it makes for
difficult to know when the request was dropped.
This commit is contained in:
Joonas Koivunen
2023-04-25 15:22:23 +03:00
committed by GitHub
parent e83684b868
commit 4911d7ce6f
1 changed files with 38 additions and 1 deletions
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39
libs/utils/src/http/endpoint.rs
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@@ -76,6 +76,7 @@ where
let log_quietly = method == Method::GET;
async move {
let cancellation_guard = RequestCancelled::warn_when_dropped_without_responding();
if log_quietly {
debug!("Handling request");
} else {
@@ -87,7 +88,11 @@ where
// Usage of the error handler also means that we expect only the `ApiError` errors to be raised in this call.
//
// Panics are not handled separately, there's a `tracing_panic_hook` from another module to do that globally.
match (self.0)(request).await {
let res = (self.0)(request).await;
cancellation_guard.disarm();
match res {
Ok(response) => {
let response_status = response.status();
if log_quietly && response_status.is_success() {
@@ -105,6 +110,38 @@ where
}
}
/// Drop guard to WARN in case the request was dropped before completion.
struct RequestCancelled {
warn: Option<tracing::Span>,
}
impl RequestCancelled {
/// Create the drop guard using the [`tracing::Span::current`] as the span.
fn warn_when_dropped_without_responding() -> Self {
RequestCancelled {
warn: Some(tracing::Span::current()),
}
}
/// Consume the drop guard without logging anything.
fn disarm(mut self) {
self.warn = None;
}
}
impl Drop for RequestCancelled {
fn drop(&mut self) {
if let Some(span) = self.warn.take() {
// the span has all of the info already, but the outer `.instrument(span)` has already
// been dropped, so we need to manually re-enter it for this message.
//
// this is what the instrument would do before polling so it is fine.
let _g = span.entered();
warn!("request was dropped before completing");
}
}
}
async fn prometheus_metrics_handler(_req: Request<Body>) -> Result<Response<Body>, ApiError> {
SERVE_METRICS_COUNT.inc();