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use opentelemetry::api::IdGenerator; use opentelemetry::{api, sdk}; use std::any::TypeId; use std::fmt; use std::marker; use std::time::SystemTime; use tracing_core::span::{self, Attributes, Id, Record}; use tracing_core::{field, Event, Subscriber}; #[cfg(feature = "tracing-log")] use tracing_log::NormalizeEvent; use tracing_subscriber::layer::Context; use tracing_subscriber::registry::LookupSpan; use tracing_subscriber::Layer; static SPAN_NAME_FIELD: &str = "otel.name"; /// An [OpenTelemetry] propagation layer for use in a project that uses /// [tracing]. /// /// [OpenTelemetry]: https://opentelemetry.io /// [tracing]: https://github.com/tokio-rs/tracing pub struct OpenTelemetryLayer<S, T: api::Tracer> { tracer: T, sampler: Box<dyn api::Sampler>, id_generator: sdk::IdGenerator, get_context: WithContext, _registry: marker::PhantomData<S>, } impl<S> Default for OpenTelemetryLayer<S, api::NoopTracer> where S: Subscriber + for<'span> LookupSpan<'span>, { fn default() -> Self { OpenTelemetryLayer::new(api::NoopTracer {}, sdk::Sampler::AlwaysOn) } } /// Construct a layer to track spans via [OpenTelemetry]. /// /// [OpenTelemetry]: https://opentelemetry.io /// /// # Examples /// /// ```rust,no_run /// use tracing_subscriber::layer::SubscriberExt; /// use tracing_subscriber::Registry; /// /// // Use the tracing subscriber `Registry`, or any other subscriber /// // that impls `LookupSpan` /// let subscriber = Registry::default() /// .with(tracing_opentelemetry::layer()); /// # drop(subscriber); /// ``` pub fn layer<S>() -> OpenTelemetryLayer<S, api::NoopTracer> where S: Subscriber + for<'span> LookupSpan<'span>, { OpenTelemetryLayer::default() } // this function "remembers" the types of the subscriber so that we // can downcast to something aware of them without knowing those // types at the callsite. // // See https://github.com/tokio-rs/tracing/blob/4dad420ee1d4607bad79270c1520673fa6266a3d/tracing-error/src/layer.rs pub(crate) struct WithContext( fn(&tracing::Dispatch, &span::Id, f: &mut dyn FnMut(&mut api::SpanBuilder, &dyn api::Sampler)), ); impl WithContext { // This function allows a function to be called in the context of the // "remembered" subscriber. pub(crate) fn with_context<'a>( &self, dispatch: &'a tracing::Dispatch, id: &span::Id, mut f: impl FnMut(&mut api::SpanBuilder, &dyn api::Sampler), ) { (self.0)(dispatch, id, &mut f) } } pub(crate) fn build_span_context( builder: &mut api::SpanBuilder, sampler: &dyn api::Sampler, ) -> api::SpanContext { let span_id = builder.span_id.expect("Builders must have id"); let (trace_id, trace_flags) = builder .parent_context .as_ref() .filter(|parent_context| parent_context.is_valid()) .map(|parent_context| (parent_context.trace_id(), parent_context.trace_flags())) .unwrap_or_else(|| { let trace_id = builder.trace_id.expect("trace_id should exist"); // ensure sampling decision is recorded so all span contexts have consistent flags let sampling_decision = if let Some(result) = builder.sampling_result.as_ref() { result.decision.clone() } else { let mut result = sampler.should_sample( builder.parent_context.as_ref(), trace_id, &builder.name, builder .span_kind .as_ref() .unwrap_or(&api::SpanKind::Internal), builder.attributes.as_ref().unwrap_or(&Vec::new()), builder.links.as_ref().unwrap_or(&Vec::new()), ); // Record additional attributes resulting from sampling if let Some(attributes) = &mut builder.attributes { attributes.append(&mut result.attributes) } else { builder.attributes = Some(result.attributes); } result.decision }; let trace_flags = if sampling_decision == api::SamplingDecision::RecordAndSampled { api::TRACE_FLAG_SAMPLED } else { 0 }; (trace_id, trace_flags) }); api::SpanContext::new(trace_id, span_id, trace_flags, false) } struct SpanEventVisitor<'a>(&'a mut api::Event); impl<'a> field::Visit for SpanEventVisitor<'a> { /// Record events on the underlying OpenTelemetry [`Span`] from `&str` values. /// /// [`Span`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/span/trait.Span.html fn record_str(&mut self, field: &field::Field, value: &str) { match field.name() { "message" => self.0.name = value.to_string(), // Skip fields that are actually log metadata that have already been handled #[cfg(feature = "tracing-log")] name if name.starts_with("log.") => (), name => { self.0.attributes.push(api::KeyValue::new(name, value)); } } } /// Record events on the underlying OpenTelemetry [`Span`] from values that /// implement Debug. /// /// [`Span`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/span/trait.Span.html fn record_debug(&mut self, field: &field::Field, value: &dyn fmt::Debug) { match field.name() { "message" => self.0.name = format!("{:?}", value), // Skip fields that are actually log metadata that have already been handled #[cfg(feature = "tracing-log")] name if name.starts_with("log.") => (), name => { self.0 .attributes .push(api::KeyValue::new(name, format!("{:?}", value))); } } } } struct SpanAttributeVisitor<'a>(&'a mut api::SpanBuilder); impl<'a> field::Visit for SpanAttributeVisitor<'a> { /// Set attributes on the underlying OpenTelemetry [`Span`] from `&str` values. /// /// [`Span`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/span/trait.Span.html fn record_str(&mut self, field: &field::Field, value: &str) { if field.name() == SPAN_NAME_FIELD { self.0.name = value.to_string(); } else { let attribute = api::KeyValue::new(field.name(), value); if let Some(attributes) = &mut self.0.attributes { attributes.push(attribute); } else { self.0.attributes = Some(vec![attribute]); } } } /// Set attributes on the underlying OpenTelemetry [`Span`] from values that /// implement Debug. /// /// [`Span`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/span/trait.Span.html fn record_debug(&mut self, field: &field::Field, value: &dyn fmt::Debug) { if field.name() == SPAN_NAME_FIELD { self.0.name = format!("{:?}", value); } else { let attribute = api::Key::new(field.name()).string(format!("{:?}", value)); if let Some(attributes) = &mut self.0.attributes { attributes.push(attribute); } else { self.0.attributes = Some(vec![attribute]); } } } } impl<S, T> OpenTelemetryLayer<S, T> where S: Subscriber + for<'span> LookupSpan<'span>, T: api::Tracer + 'static, { /// Set the [`Tracer`] and [`Sampler`] that this layer will use to produce and /// track OpenTelemetry [`Span`]s. /// /// [`Tracer`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/tracer/trait.Tracer.html /// [`Sampler`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/sampler/trait.Sampler.html /// [`Span`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/span/trait.Span.html /// /// # Examples /// /// ```rust,no_run /// use opentelemetry::{api::Provider, sdk}; /// use tracing_opentelemetry::OpenTelemetryLayer; /// use tracing_subscriber::layer::SubscriberExt; /// use tracing_subscriber::Registry; /// /// // Create a jaeger exporter for a `trace-demo` service. /// let exporter = opentelemetry_jaeger::Exporter::builder() /// .with_agent_endpoint("127.0.0.1:6831".parse().unwrap()) /// .with_process(opentelemetry_jaeger::Process { /// service_name: "trace_demo".to_string(), /// tags: Vec::new(), /// }) /// .init().expect("Error initializing Jaeger exporter"); /// /// // Build a provider from the jaeger exporter that always samples. /// let provider = sdk::Provider::builder() /// .with_simple_exporter(exporter) /// .with_config(sdk::Config { /// default_sampler: Box::new(sdk::Sampler::AlwaysOn), /// ..Default::default() /// }) /// .build(); /// /// // Get a tracer from the provider for a component /// let tracer = provider.get_tracer("component-name"); /// /// // The probability sampler can be used to export a percentage of spans /// let sampler = sdk::Sampler::Probability(0.33); /// /// // Create a layer with the configured tracer /// let otel_layer = OpenTelemetryLayer::new(tracer, sampler); /// /// // Use the tracing subscriber `Registry`, or any other subscriber /// // that impls `LookupSpan` /// let subscriber = Registry::default() /// .with(otel_layer); /// # drop(subscriber); /// ``` pub fn new<Sampler>(tracer: T, sampler: Sampler) -> Self where Sampler: api::Sampler + 'static, { OpenTelemetryLayer { tracer, sampler: Box::new(sampler), id_generator: sdk::IdGenerator::default(), get_context: WithContext(Self::get_context), _registry: marker::PhantomData, } } /// Set the [`Tracer`] that this layer will use to produce and track /// OpenTelemetry [`Span`]s. /// /// [`Tracer`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/tracer/trait.Tracer.html /// [`Span`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/span/trait.Span.html /// /// # Examples /// /// ```rust,no_run /// use opentelemetry::{api::Provider, sdk}; /// use tracing_subscriber::layer::SubscriberExt; /// use tracing_subscriber::Registry; /// /// // Create a jaeger exporter for a `trace-demo` service. /// let exporter = opentelemetry_jaeger::Exporter::builder() /// .with_agent_endpoint("127.0.0.1:6831".parse().unwrap()) /// .with_process(opentelemetry_jaeger::Process { /// service_name: "trace_demo".to_string(), /// tags: Vec::new(), /// }) /// .init().expect("Error initializing Jaeger exporter"); /// /// // Build a provider from the jaeger exporter that always samples. /// let provider = sdk::Provider::builder() /// .with_simple_exporter(exporter) /// .with_config(sdk::Config { /// default_sampler: Box::new(sdk::Sampler::AlwaysOn), /// ..Default::default() /// }) /// .build(); /// /// // Get a tracer from the provider for a component /// let tracer = provider.get_tracer("component-name"); /// /// // Create a layer with the configured tracer /// let otel_layer = tracing_opentelemetry::layer().with_tracer(tracer); /// /// // Use the tracing subscriber `Registry`, or any other subscriber /// // that impls `LookupSpan` /// let subscriber = Registry::default() /// .with(otel_layer); /// # drop(subscriber); /// ``` pub fn with_tracer<Tracer>(self, tracer: Tracer) -> OpenTelemetryLayer<S, Tracer> where Tracer: api::Tracer + 'static, { OpenTelemetryLayer { tracer, sampler: self.sampler, id_generator: self.id_generator, get_context: WithContext(OpenTelemetryLayer::<S, Tracer>::get_context), _registry: self._registry, } } /// Set the [`Sampler`] to configure the logic around which [`Span`]s are /// exported. /// /// [`Sampler`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/sampler/trait.Sampler.html /// [`Span`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/span/trait.Span.html /// /// # Examples /// /// ```rust,no_run /// use opentelemetry::sdk; /// use tracing_subscriber::layer::SubscriberExt; /// use tracing_subscriber::Registry; /// /// // The probability sampler can be used to export a percentage of spans /// let sampler = sdk::Sampler::Probability(0.33); /// /// // Create a layer with the configured sampler /// let otel_layer = tracing_opentelemetry::layer().with_sampler(sampler); /// /// // Use the tracing subscriber `Registry`, or any other subscriber /// // that impls `LookupSpan` /// let subscriber = Registry::default() /// .with(otel_layer); /// # drop(subscriber); /// ``` pub fn with_sampler<Sampler>(self, sampler: Sampler) -> Self where Sampler: api::Sampler + 'static, { OpenTelemetryLayer { sampler: Box::new(sampler), ..self } } /// Retrieve the parent OpenTelemetry [`SpanContext`] from the current /// tracing [`span`] through the [`Registry`]. This [`SpanContext`] /// links spans to their parent for proper hierarchical visualization. /// /// [`SpanContext`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/span_context/struct.SpanContext.html /// [`span`]: https://docs.rs/tracing/latest/tracing/struct.Span.html /// [`Registry`]: https://docs.rs/tracing-subscriber/latest/tracing_subscriber/struct.Registry.html fn parent_span_context( &self, attrs: &Attributes<'_>, ctx: &Context<'_, S>, ) -> Option<api::SpanContext> { // If a span is specified, it _should_ exist in the underlying `Registry`. if let Some(parent) = attrs.parent() { let span = ctx.span(parent).expect("Span not found, this is a bug"); let mut extensions = span.extensions_mut(); extensions .get_mut::<api::SpanBuilder>() .map(|builder| build_span_context(builder, self.sampler.as_ref())) // Else if the span is inferred from context, look up any available current span. } else if attrs.is_contextual() { ctx.lookup_current().and_then(|span| { let mut extensions = span.extensions_mut(); extensions .get_mut::<api::SpanBuilder>() .map(|builder| build_span_context(builder, self.sampler.as_ref())) }) // Explicit root spans should have no parent context. } else { None } } fn get_context( dispatch: &tracing::Dispatch, id: &span::Id, f: &mut dyn FnMut(&mut api::SpanBuilder, &dyn api::Sampler), ) { let subscriber = dispatch .downcast_ref::<S>() .expect("subscriber should downcast to expected type; this is a bug!"); let span = subscriber .span(id) .expect("registry should have a span for the current ID"); let layer = dispatch .downcast_ref::<OpenTelemetryLayer<S, T>>() .expect("layer should downcast to expected type; this is a bug!"); let mut extensions = span.extensions_mut(); if let Some(builder) = extensions.get_mut::<api::SpanBuilder>() { f(builder, layer.sampler.as_ref()); } } } impl<S, T> Layer<S> for OpenTelemetryLayer<S, T> where S: Subscriber + for<'span> LookupSpan<'span>, T: api::Tracer + 'static, { /// Creates an [OpenTelemetry `Span`] for the corresponding [tracing `Span`]. /// /// [OpenTelemetry `Span`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/span/trait.Span.html /// [tracing `Span`]: https://docs.rs/tracing/latest/tracing/struct.Span.html fn new_span(&self, attrs: &Attributes<'_>, id: &span::Id, ctx: Context<'_, S>) { let span = ctx.span(id).expect("Span not found, this is a bug"); let mut extensions = span.extensions_mut(); let mut builder = self .tracer .span_builder(attrs.metadata().name()) .with_start_time(SystemTime::now()) // Eagerly assign span id so children have stable parent id .with_span_id(self.id_generator.new_span_id()); // Set optional parent span context from attrs builder.parent_context = self.parent_span_context(attrs, &ctx); // Ensure trace id exists so children are matched properly. if builder.parent_context.is_none() { builder.trace_id = Some(self.id_generator.new_trace_id()); } attrs.record(&mut SpanAttributeVisitor(&mut builder)); extensions.insert(builder); } /// Record OpenTelemetry [`attributes`] for the given values. /// /// [`attributes`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/tracer/struct.SpanBuilder.html#structfield.attributes fn on_record(&self, id: &Id, values: &Record<'_>, ctx: Context<'_, S>) { let span = ctx.span(id).expect("Span not found, this is a bug"); let mut extensions = span.extensions_mut(); if let Some(builder) = extensions.get_mut::<api::SpanBuilder>() { values.record(&mut SpanAttributeVisitor(builder)); } } fn on_follows_from(&self, id: &Id, follows: &Id, ctx: Context<S>) { let span = ctx.span(id).expect("Span not found, this is a bug"); let mut extensions = span.extensions_mut(); let builder = extensions .get_mut::<api::SpanBuilder>() .expect("Missing SpanBuilder span extensions"); let follows_span = ctx .span(follows) .expect("Span to follow not found, this is a bug"); let mut follows_extensions = follows_span.extensions_mut(); let follows_builder = follows_extensions .get_mut::<api::SpanBuilder>() .expect("Missing SpanBuilder span extensions"); let follows_context = build_span_context(follows_builder, self.sampler.as_ref()); let follows_link = api::Link::new(follows_context, Vec::new()); if let Some(ref mut links) = builder.links { links.push(follows_link); } else { builder.links = Some(vec![follows_link]); } } /// Records OpenTelemetry [`Event`] data on event. /// /// Note: an [`ERROR`]-level event will also set the OpenTelemetry span status code to /// [`Unknown`], signaling that an error has occurred. /// /// [`Event`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/event/struct.Event.html /// [`ERROR`]: https://docs.rs/tracing/latest/tracing/struct.Level.html#associatedconstant.ERROR /// [`Unknown`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/span/enum.StatusCode.html#variant.Unknown fn on_event(&self, event: &Event<'_>, ctx: Context<'_, S>) { // Ignore events that are not in the context of a span if let Some(span) = ctx.lookup_current() { // Performing read operations before getting a write lock to avoid a deadlock // See https://github.com/tokio-rs/tracing/issues/763 #[cfg(feature = "tracing-log")] let normalized_meta = event.normalized_metadata(); #[cfg(feature = "tracing-log")] let meta = normalized_meta.as_ref().unwrap_or_else(|| event.metadata()); #[cfg(not(feature = "tracing-log"))] let meta = event.metadata(); let mut otel_event = api::Event::new( String::new(), SystemTime::now(), vec![ api::Key::new("level").string(meta.level().to_string()), api::Key::new("target").string(meta.target()), ], ); event.record(&mut SpanEventVisitor(&mut otel_event)); let mut extensions = span.extensions_mut(); if let Some(builder) = extensions.get_mut::<api::SpanBuilder>() { if builder.status_code.is_none() && *meta.level() == tracing_core::Level::ERROR { builder.status_code = Some(api::StatusCode::Unknown); } if let Some(ref mut events) = builder.message_events { events.push(otel_event); } else { builder.message_events = Some(vec![otel_event]); } } }; } /// Exports an OpenTelemetry [`Span`] on close. /// /// [`Span`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/span/trait.Span.html fn on_close(&self, id: span::Id, ctx: Context<'_, S>) { let span = ctx.span(&id).expect("Span not found, this is a bug"); let mut extensions = span.extensions_mut(); if let Some(builder) = extensions.remove::<api::SpanBuilder>() { // Assign end time, build and start span, drop span to export builder.with_end_time(SystemTime::now()).start(&self.tracer); } } // SAFETY: this is safe because the `WithContext` function pointer is valid // for the lifetime of `&self`. unsafe fn downcast_raw(&self, id: TypeId) -> Option<*const ()> { match id { id if id == TypeId::of::<Self>() => Some(self as *const _ as *const ()), id if id == TypeId::of::<WithContext>() => { Some(&self.get_context as *const _ as *const ()) } _ => None, } } } #[cfg(test)] mod tests { use super::*; use opentelemetry::api; use std::sync::{Arc, Mutex}; use tracing_subscriber::prelude::*; #[derive(Debug, Clone)] struct TestTracer(Arc<Mutex<Option<api::SpanBuilder>>>); impl api::Tracer for TestTracer { type Span = api::NoopSpan; fn invalid(&self) -> Self::Span { api::NoopSpan::new() } fn start_from_context(&self, _name: &str, _context: &api::Context) -> Self::Span { self.invalid() } fn span_builder(&self, name: &str) -> api::SpanBuilder { api::SpanBuilder::from_name(name.to_string()) } fn build_with_context(&self, builder: api::SpanBuilder, _cx: &api::Context) -> Self::Span { *self.0.lock().unwrap() = Some(builder); self.invalid() } } #[test] fn dynamic_span_names() { let dynamic_name = "GET http://example.com".to_string(); let tracer = TestTracer(Arc::new(Mutex::new(None))); let subscriber = tracing_subscriber::registry().with(layer().with_tracer(tracer.clone())); tracing::subscriber::with_default(subscriber, || { tracing::debug_span!("static_name", otel.name = dynamic_name.as_str()); }); let recorded_name = tracer.0.lock().unwrap().as_ref().map(|b| b.name.clone()); assert_eq!(recorded_name, Some(dynamic_name)) } }