opentelemetry/context/
future_ext.rs

1use crate::Context;
2use futures_core::Stream;
3use futures_sink::Sink;
4use pin_project_lite::pin_project;
5use std::pin::Pin;
6use std::task::Context as TaskContext;
7use std::task::Poll;
8impl<T: Sized> FutureExt for T {}
9
10impl<T: std::future::Future> std::future::Future for WithContext<T> {
11    type Output = T::Output;
12
13    fn poll(self: Pin<&mut Self>, task_cx: &mut TaskContext<'_>) -> Poll<Self::Output> {
14        let this = self.project();
15        let _guard = this.otel_cx.clone().attach();
16
17        this.inner.poll(task_cx)
18    }
19}
20
21impl<T: Stream> Stream for WithContext<T> {
22    type Item = T::Item;
23
24    fn poll_next(self: Pin<&mut Self>, task_cx: &mut TaskContext<'_>) -> Poll<Option<Self::Item>> {
25        let this = self.project();
26        let _guard = this.otel_cx.clone().attach();
27        T::poll_next(this.inner, task_cx)
28    }
29}
30
31pin_project! {
32    /// A future, stream, or sink that has an associated context.
33    #[derive(Clone, Debug)]
34    pub struct WithContext<T> {
35        #[pin]
36        inner: T,
37        otel_cx: Context,
38    }
39}
40
41impl<I, T: Sink<I>> Sink<I> for WithContext<T>
42where
43    T: Sink<I>,
44{
45    type Error = T::Error;
46
47    fn poll_ready(
48        self: Pin<&mut Self>,
49        task_cx: &mut TaskContext<'_>,
50    ) -> Poll<Result<(), Self::Error>> {
51        let this = self.project();
52        let _guard = this.otel_cx.clone().attach();
53        T::poll_ready(this.inner, task_cx)
54    }
55
56    fn start_send(self: Pin<&mut Self>, item: I) -> Result<(), Self::Error> {
57        let this = self.project();
58        let _guard = this.otel_cx.clone().attach();
59        T::start_send(this.inner, item)
60    }
61
62    fn poll_flush(
63        self: Pin<&mut Self>,
64        task_cx: &mut TaskContext<'_>,
65    ) -> Poll<Result<(), Self::Error>> {
66        let this = self.project();
67        let _guard = this.otel_cx.clone().attach();
68        T::poll_flush(this.inner, task_cx)
69    }
70
71    fn poll_close(
72        self: Pin<&mut Self>,
73        task_cx: &mut TaskContext<'_>,
74    ) -> Poll<Result<(), Self::Error>> {
75        let this = self.project();
76        let _enter = this.otel_cx.clone().attach();
77        T::poll_close(this.inner, task_cx)
78    }
79}
80
81/// Extension trait allowing futures, streams, and sinks to be traced with a span.
82pub trait FutureExt: Sized {
83    /// Attaches the provided [`Context`] to this type, returning a `WithContext`
84    /// wrapper.
85    ///
86    /// When the wrapped type is a future, stream, or sink, the attached context
87    /// will be set as current while it is being polled.
88    ///
89    /// [`Context`]: Context
90    fn with_context(self, otel_cx: Context) -> WithContext<Self> {
91        WithContext {
92            inner: self,
93            otel_cx,
94        }
95    }
96
97    /// Attaches the current [`Context`] to this type, returning a `WithContext`
98    /// wrapper.
99    ///
100    /// When the wrapped type is a future, stream, or sink, the attached context
101    /// will be set as the default while it is being polled.
102    ///
103    /// [`Context`]: Context
104    fn with_current_context(self) -> WithContext<Self> {
105        let otel_cx = Context::current();
106        self.with_context(otel_cx)
107    }
108}
opentelemetry/context/future_ext.rs

opentelemetry/context/
future_ext.rs
