opentelemetry/trace/context.rs
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//! Context extensions for tracing
use crate::{
global,
trace::{Span, SpanContext, Status},
Context, ContextGuard, KeyValue,
};
use futures_core::stream::Stream;
use futures_sink::Sink;
use pin_project_lite::pin_project;
use std::{
borrow::Cow,
error::Error,
pin::Pin,
sync::Mutex,
task::{Context as TaskContext, Poll},
};
const NOOP_SPAN: SynchronizedSpan = SynchronizedSpan {
span_context: SpanContext::NONE,
inner: None,
};
/// A reference to the currently active span in this context.
#[derive(Debug)]
pub struct SpanRef<'a>(&'a SynchronizedSpan);
#[derive(Debug)]
pub(crate) struct SynchronizedSpan {
/// Immutable span context
span_context: SpanContext,
/// Mutable span inner that requires synchronization
inner: Option<Mutex<global::BoxedSpan>>,
}
impl From<SpanContext> for SynchronizedSpan {
fn from(value: SpanContext) -> Self {
Self {
span_context: value,
inner: None,
}
}
}
impl<T: Span + Send + Sync + 'static> From<T> for SynchronizedSpan {
fn from(value: T) -> Self {
Self {
span_context: value.span_context().clone(),
inner: Some(Mutex::new(global::BoxedSpan::new(value))),
}
}
}
impl SpanRef<'_> {
fn with_inner_mut<F: FnOnce(&mut global::BoxedSpan)>(&self, f: F) {
if let Some(ref inner) = self.0.inner {
match inner.lock() {
Ok(mut locked) => f(&mut locked),
Err(err) => global::handle_error(err),
}
}
}
}
impl SpanRef<'_> {
/// Record an event in the context this span.
///
/// Note that the OpenTelemetry project documents certain "[standard
/// attributes]" that have prescribed semantic meanings and are available via
/// the [opentelemetry_semantic_conventions] crate.
///
/// [standard attributes]: https://github.com/open-telemetry/opentelemetry-specification/blob/v1.9.0/specification/trace/semantic_conventions/README.md
/// [opentelemetry_semantic_conventions]: https://docs.rs/opentelemetry-semantic-conventions
pub fn add_event<T>(&self, name: T, attributes: Vec<KeyValue>)
where
T: Into<Cow<'static, str>>,
{
self.with_inner_mut(|inner| inner.add_event(name, attributes))
}
/// Record an error as an event for this span.
///
/// An additional call to [Span::set_status] is required if the status of the
/// span should be set to error, as this method does not change the span status.
///
/// If this span is not being recorded then this method does nothing.
pub fn record_error(&self, err: &dyn Error) {
self.with_inner_mut(|inner| inner.record_error(err))
}
/// Record an event with a timestamp in the context this span.
///
/// Note that the OpenTelemetry project documents certain "[standard
/// attributes]" that have prescribed semantic meanings and are available via
/// the [opentelemetry_semantic_conventions] crate.
///
/// [standard attributes]: https://github.com/open-telemetry/opentelemetry-specification/blob/v1.9.0/specification/trace/semantic_conventions/README.md
/// [opentelemetry_semantic_conventions]: https://docs.rs/opentelemetry-semantic-conventions
pub fn add_event_with_timestamp<T>(
&self,
name: T,
timestamp: std::time::SystemTime,
attributes: Vec<crate::KeyValue>,
) where
T: Into<Cow<'static, str>>,
{
self.with_inner_mut(move |inner| {
inner.add_event_with_timestamp(name, timestamp, attributes)
})
}
/// A reference to the [`SpanContext`] for this span.
pub fn span_context(&self) -> &SpanContext {
&self.0.span_context
}
/// Returns `true` if this span is recording information.
///
/// Spans will not be recording information after they have ended.
///
/// This flag may be `true` despite the entire trace being sampled out. This
/// allows recording and processing of information about the individual
/// spans without sending it to the backend. An example of this scenario may
/// be recording and processing of all incoming requests for the processing
/// and building of SLA/SLO latency charts while sending only a subset -
/// sampled spans - to the backend.
pub fn is_recording(&self) -> bool {
self.0
.inner
.as_ref()
.and_then(|inner| inner.lock().ok().map(|active| active.is_recording()))
.unwrap_or(false)
}
/// Set an attribute of this span.
///
/// Setting an attribute with the same key as an existing attribute
/// generally overwrites the existing attribute's value.
///
/// Note that the OpenTelemetry project documents certain "[standard
/// attributes]" that have prescribed semantic meanings and are available via
/// the [opentelemetry_semantic_conventions] crate.
///
/// [standard attributes]: https://github.com/open-telemetry/opentelemetry-specification/blob/v1.9.0/specification/trace/semantic_conventions/README.md
/// [opentelemetry_semantic_conventions]: https://docs.rs/opentelemetry-semantic-conventions
pub fn set_attribute(&self, attribute: crate::KeyValue) {
self.with_inner_mut(move |inner| inner.set_attribute(attribute))
}
/// Set multiple attributes of this span.
///
/// Setting an attribute with the same key as an existing attribute
/// generally overwrites the existing attribute's value.
///
/// Note that the OpenTelemetry project documents certain "[standard
/// attributes]" that have prescribed semantic meanings and are available via
/// the [opentelemetry_semantic_conventions] crate.
///
/// [standard attributes]: https://github.com/open-telemetry/opentelemetry-specification/blob/v1.9.0/specification/trace/semantic_conventions/README.md
/// [opentelemetry_semantic_conventions]: https://docs.rs/opentelemetry-semantic-conventions
pub fn set_attributes(&self, attributes: impl IntoIterator<Item = KeyValue>) {
self.with_inner_mut(move |inner| inner.set_attributes(attributes))
}
/// Sets the status of this `Span`.
///
/// If used, this will override the default span status, which is [`Status::Unset`].
pub fn set_status(&self, status: Status) {
self.with_inner_mut(move |inner| inner.set_status(status))
}
/// Updates the span's name.
///
/// After this update, any sampling behavior based on the name will depend on
/// the implementation.
pub fn update_name<T>(&self, new_name: T)
where
T: Into<Cow<'static, str>>,
{
self.with_inner_mut(move |inner| inner.update_name(new_name))
}
/// Signals that the operation described by this span has now ended.
pub fn end(&self) {
self.end_with_timestamp(crate::time::now());
}
/// Signals that the operation described by this span ended at the given time.
pub fn end_with_timestamp(&self, timestamp: std::time::SystemTime) {
self.with_inner_mut(move |inner| inner.end_with_timestamp(timestamp))
}
}
/// Methods for storing and retrieving trace data in a [`Context`].
///
/// See [`Context`] for examples of setting and retrieving the current context.
pub trait TraceContextExt {
/// Returns a clone of the current context with the included [`Span`].
///
/// # Examples
///
/// ```
/// use opentelemetry::{global, trace::{TraceContextExt, Tracer}, Context};
///
/// let tracer = global::tracer("example");
///
/// // build a span
/// let span = tracer.start("parent_span");
///
/// // create a new context from the currently active context that includes this span
/// let cx = Context::current_with_span(span);
///
/// // create a child span by explicitly specifying the parent context
/// let child = tracer.start_with_context("child_span", &cx);
/// # drop(child)
/// ```
fn current_with_span<T: crate::trace::Span + Send + Sync + 'static>(span: T) -> Self;
/// Returns a clone of this context with the included span.
///
/// # Examples
///
/// ```
/// use opentelemetry::{global, trace::{TraceContextExt, Tracer}, Context};
///
/// fn fn_with_passed_in_context(cx: &Context) {
/// let tracer = global::tracer("example");
///
/// // build a span
/// let span = tracer.start("parent_span");
///
/// // create a new context from the given context that includes the span
/// let cx_with_parent = cx.with_span(span);
///
/// // create a child span by explicitly specifying the parent context
/// let child = tracer.start_with_context("child_span", &cx_with_parent);
/// # drop(child)
/// }
///
fn with_span<T: crate::trace::Span + Send + Sync + 'static>(&self, span: T) -> Self;
/// Returns a reference to this context's span, or the default no-op span if
/// none has been set.
///
/// # Examples
///
/// ```
/// use opentelemetry::{trace::TraceContextExt, Context};
///
/// // Add an event to the currently active span
/// Context::map_current(|cx| cx.span().add_event("An event!", vec![]));
/// ```
fn span(&self) -> SpanRef<'_>;
/// Returns whether or not an active span has been set.
///
/// # Examples
///
/// ```
/// use opentelemetry::{trace::TraceContextExt, Context};
///
/// assert!(!Context::map_current(|cx| cx.has_active_span()));
/// ```
fn has_active_span(&self) -> bool;
/// Returns a copy of this context with the span context included.
///
/// This is useful for building propagators.
fn with_remote_span_context(&self, span_context: crate::trace::SpanContext) -> Self;
}
impl TraceContextExt for Context {
fn current_with_span<T: crate::trace::Span + Send + Sync + 'static>(span: T) -> Self {
Context::current_with_synchronized_span(span.into())
}
fn with_span<T: crate::trace::Span + Send + Sync + 'static>(&self, span: T) -> Self {
self.with_synchronized_span(span.into())
}
fn span(&self) -> SpanRef<'_> {
if let Some(span) = self.span.as_ref() {
SpanRef(span)
} else {
SpanRef(&NOOP_SPAN)
}
}
fn has_active_span(&self) -> bool {
self.span.is_some()
}
fn with_remote_span_context(&self, span_context: crate::trace::SpanContext) -> Self {
self.with_synchronized_span(span_context.into())
}
}
/// Mark a given `Span` as active.
///
/// The `Tracer` MUST provide a way to update its active `Span`, and MAY provide convenience
/// methods to manage a `Span`'s lifetime and the scope in which a `Span` is active. When an
/// active `Span` is made inactive, the previously-active `Span` SHOULD be made active. A `Span`
/// maybe finished (i.e. have a non-null end time) but still be active. A `Span` may be active
/// on one thread after it has been made inactive on another.
///
/// # Examples
///
/// ```
/// use opentelemetry::{global, trace::{Span, Tracer}, KeyValue};
/// use opentelemetry::trace::{get_active_span, mark_span_as_active};
///
/// fn my_function() {
/// let tracer = global::tracer("my-component-a");
/// // start an active span in one function
/// let span = tracer.start("span-name");
/// let _guard = mark_span_as_active(span);
/// // anything happening in functions we call can still access the active span...
/// my_other_function();
/// }
///
/// fn my_other_function() {
/// // call methods on the current span from
/// get_active_span(|span| {
/// span.add_event("An event!".to_string(), vec![KeyValue::new("happened", true)]);
/// });
/// }
/// ```
#[must_use = "Dropping the guard detaches the context."]
pub fn mark_span_as_active<T: crate::trace::Span + Send + Sync + 'static>(span: T) -> ContextGuard {
let cx = Context::current_with_span(span);
cx.attach()
}
/// Executes a closure with a reference to this thread's current span.
///
/// # Examples
///
/// ```
/// use opentelemetry::{global, trace::{Span, Tracer}, KeyValue};
/// use opentelemetry::trace::get_active_span;
///
/// fn my_function() {
/// // start an active span in one function
/// global::tracer("my-component").in_span("span-name", |_cx| {
/// // anything happening in functions we call can still access the active span...
/// my_other_function();
/// })
/// }
///
/// fn my_other_function() {
/// // call methods on the current span from
/// get_active_span(|span| {
/// span.add_event("An event!", vec![KeyValue::new("happened", true)]);
/// })
/// }
/// ```
pub fn get_active_span<F, T>(f: F) -> T
where
F: FnOnce(SpanRef<'_>) -> T,
{
Context::map_current(|cx| f(cx.span()))
}
pin_project! {
/// A future, stream, or sink that has an associated context.
#[derive(Clone, Debug)]
pub struct WithContext<T> {
#[pin]
inner: T,
otel_cx: Context,
}
}
impl<T: Sized> FutureExt for T {}
impl<T: std::future::Future> std::future::Future for WithContext<T> {
type Output = T::Output;
fn poll(self: Pin<&mut Self>, task_cx: &mut TaskContext<'_>) -> Poll<Self::Output> {
let this = self.project();
let _guard = this.otel_cx.clone().attach();
this.inner.poll(task_cx)
}
}
impl<T: Stream> Stream for WithContext<T> {
type Item = T::Item;
fn poll_next(self: Pin<&mut Self>, task_cx: &mut TaskContext<'_>) -> Poll<Option<Self::Item>> {
let this = self.project();
let _guard = this.otel_cx.clone().attach();
T::poll_next(this.inner, task_cx)
}
}
impl<I, T: Sink<I>> Sink<I> for WithContext<T>
where
T: Sink<I>,
{
type Error = T::Error;
fn poll_ready(
self: Pin<&mut Self>,
task_cx: &mut TaskContext<'_>,
) -> Poll<Result<(), Self::Error>> {
let this = self.project();
let _guard = this.otel_cx.clone().attach();
T::poll_ready(this.inner, task_cx)
}
fn start_send(self: Pin<&mut Self>, item: I) -> Result<(), Self::Error> {
let this = self.project();
let _guard = this.otel_cx.clone().attach();
T::start_send(this.inner, item)
}
fn poll_flush(
self: Pin<&mut Self>,
task_cx: &mut TaskContext<'_>,
) -> Poll<Result<(), Self::Error>> {
let this = self.project();
let _guard = this.otel_cx.clone().attach();
T::poll_flush(this.inner, task_cx)
}
fn poll_close(
self: Pin<&mut Self>,
task_cx: &mut TaskContext<'_>,
) -> Poll<Result<(), Self::Error>> {
let this = self.project();
let _enter = this.otel_cx.clone().attach();
T::poll_close(this.inner, task_cx)
}
}
/// Extension trait allowing futures, streams, and sinks to be traced with a span.
pub trait FutureExt: Sized {
/// Attaches the provided [`Context`] to this type, returning a `WithContext`
/// wrapper.
///
/// When the wrapped type is a future, stream, or sink, the attached context
/// will be set as current while it is being polled.
///
/// [`Context`]: crate::Context
fn with_context(self, otel_cx: Context) -> WithContext<Self> {
WithContext {
inner: self,
otel_cx,
}
}
/// Attaches the current [`Context`] to this type, returning a `WithContext`
/// wrapper.
///
/// When the wrapped type is a future, stream, or sink, the attached context
/// will be set as the default while it is being polled.
///
/// [`Context`]: crate::Context
fn with_current_context(self) -> WithContext<Self> {
let otel_cx = Context::current();
self.with_context(otel_cx)
}
}