1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
//! 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)
    }
}