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Move the in-flight counter decrement to a drop guard

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This commit is contained in:
Quentin Gliech
2022-09-19 14:20:54 +02:00
parent 56fdb64a84
commit e9fd0eb36a
1 changed files with 28 additions and 3 deletions
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31
crates/http/src/layers/otel/service.rs
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@ -18,6 +18,7 @@ use futures_util::{future::BoxFuture, FutureExt as _};
use opentelemetry::{
metrics::{Counter, Histogram, UpDownCounter},
trace::{FutureExt as _, TraceContextExt},
Context, KeyValue,
};
use tower::Service;
@ -74,6 +75,29 @@ impl<ExtractContext, InjectContext, MakeSpanBuilder, OnResponse, OnError, S>
}
}
struct InFlightGuard {
context: Context,
meter: UpDownCounter<i64>,
attributes: Vec<KeyValue>,
}
impl InFlightGuard {
fn increment(context: &Context, meter: &UpDownCounter<i64>, attributes: &[KeyValue]) -> Self {
meter.add(context, 1, attributes);
Self {
context: context.clone(),
meter: meter.clone(),
attributes: attributes.to_vec(),
}
}
}
impl Drop for InFlightGuard {
fn drop(&mut self) {
self.meter.add(&self.context, -1, &self.attributes);
}
}
impl<Req, S, ExtractContextT, InjectContextT, MakeSpanBuilderT, OnResponseT, OnErrorT> Service<Req>
for Trace<ExtractContextT, InjectContextT, MakeSpanBuilderT, OnResponseT, OnErrorT, S>
where
@ -94,7 +118,6 @@ where
}
fn call(&mut self, request: Req) -> Self::Future {
let inflight_requests = self.inflight_requests.clone();
let request_counter = self.request_counter.clone();
let request_histogram = self.request_histogram.clone();
let start_time = SystemTime::now();
@ -106,7 +129,7 @@ where
let cx = cx.with_span(span);
let request = self.inject_context.inject_context(&cx, request);
inflight_requests.add(&cx, 1, &metrics_labels);
let guard = InFlightGuard::increment(&cx, &self.inflight_requests, &metrics_labels);
let on_response = self.on_response.clone();
let on_error = self.on_error.clone();
@ -116,7 +139,9 @@ where
.call(request)
.with_context(cx.clone())
.inspect(move |r| {
inflight_requests.add(&cx, -1, &metrics_labels);
// This ensures the guard gets moved to the future. In case the future panics,
// it will be dropped anyway, ensuring the in-flight counter stays accurate
let _guard = guard;
let span = cx.span();
let extra_labels = match r {