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opentelemetry: Add PreSampledTracer interface #962

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Sep 1, 2020
Merged

opentelemetry: Add PreSampledTracer interface #962

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79e9152
opentelemetry: Add PreSampledTracer interface
jtescher Sep 1, 2020
c1f2c16
Add newline
jtescher Sep 1, 2020
ab38190
Add trait docs
jtescher Sep 1, 2020
1f7fdf0
Fix malformed link
jtescher Sep 1, 2020
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157 changes: 34 additions & 123 deletions tracing-opentelemetry/src/layer.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
use opentelemetry::api::{Context as OtelContext, IdGenerator, TraceContextExt};
use opentelemetry::{api, sdk};
use crate::PreSampledTracer;
use opentelemetry::api::{self, Context as OtelContext, TraceContextExt};
use std::any::TypeId;
use std::fmt;
use std::marker;
Expand All @@ -20,10 +20,8 @@ static SPAN_KIND_FIELD: &str = "otel.kind";
///
/// [OpenTelemetry]: https://opentelemetry.io
/// [tracing]: https://github.com/tokio-rs/tracing
pub struct OpenTelemetryLayer<S, T: api::Tracer> {
pub struct OpenTelemetryLayer<S, T> {
tracer: T,
sampler: Box<dyn sdk::ShouldSample>,
id_generator: sdk::IdGenerator,

get_context: WithContext,
_registry: marker::PhantomData<S>,
Expand All @@ -34,7 +32,7 @@ where
S: Subscriber + for<'span> LookupSpan<'span>,
{
fn default() -> Self {
OpenTelemetryLayer::new(api::NoopTracer {}, sdk::Sampler::AlwaysOn)
OpenTelemetryLayer::new(api::NoopTracer {})
}
}

Expand All @@ -50,8 +48,7 @@ where
///
/// // Use the tracing subscriber `Registry`, or any other subscriber
/// // that impls `LookupSpan`
/// let subscriber = Registry::default()
/// .with(tracing_opentelemetry::layer());
/// let subscriber = Registry::default().with(tracing_opentelemetry::layer());
/// # drop(subscriber);
/// ```
pub fn layer<S>() -> OpenTelemetryLayer<S, api::NoopTracer>
Expand All @@ -70,7 +67,7 @@ pub(crate) struct WithContext(
fn(
&tracing::Dispatch,
&span::Id,
f: &mut dyn FnMut(&mut api::SpanBuilder, &dyn sdk::ShouldSample),
f: &mut dyn FnMut(&mut api::SpanBuilder, &dyn PreSampledTracer),
),
);

Expand All @@ -81,63 +78,12 @@ impl WithContext {
&self,
dispatch: &'a tracing::Dispatch,
id: &span::Id,
mut f: impl FnMut(&mut api::SpanBuilder, &dyn sdk::ShouldSample),
mut f: impl FnMut(&mut api::SpanBuilder, &dyn PreSampledTracer),
) {
(self.0)(dispatch, id, &mut f)
}
}

pub(crate) fn build_span_context(
builder: &mut api::SpanBuilder,
sampler: &dyn sdk::ShouldSample,
) -> 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 == sdk::SamplingDecision::RecordAndSampled {
api::TRACE_FLAG_SAMPLED
} else {
0
};

(trace_id, trace_flags)
});

api::SpanContext::new(trace_id, span_id, trace_flags, false)
}

fn str_to_span_kind(s: &str) -> Option<api::SpanKind> {
if s.eq_ignore_ascii_case("SERVER") {
Some(api::SpanKind::Server)
Expand Down Expand Up @@ -235,13 +181,12 @@ impl<'a> field::Visit for SpanAttributeVisitor<'a> {
impl<S, T> OpenTelemetryLayer<S, T>
where
S: Subscriber + for<'span> LookupSpan<'span>,
T: api::Tracer + 'static,
T: api::Tracer + PreSampledTracer + 'static,
{
/// Set the [`Tracer`] and [`Sampler`] that this layer will use to produce and
/// track OpenTelemetry [`Span`]s.
/// 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
/// [`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
Expand Down Expand Up @@ -273,26 +218,17 @@ where
/// // 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);
/// let otel_layer = OpenTelemetryLayer::new(tracer);
///
/// // Use the tracing subscriber `Registry`, or any other subscriber
/// // that impls `LookupSpan`
/// let subscriber = Registry::default()
/// .with(otel_layer);
/// let subscriber = Registry::default().with(otel_layer);
/// # drop(subscriber);
/// ```
pub fn new<Sampler>(tracer: T, sampler: Sampler) -> Self
where
Sampler: sdk::ShouldSample + 'static,
{
Comment on lines -288 to -291
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This is a breaking API change --- does it make sense to leave the new constructor as-is, and add a new constructor that takes just a tracer, or does that not make sense?

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Could keep as is for a deprecation cycle, the sampler is no longer needed but the method could still accept one.

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Actually deprecation isn't really what we want here unless we want another name, but with_tracer already exists. Maybe best to just go with the breaking change as it is trivial to not include the parameter and it would only be called once during initialization.

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Okay, I'm fine with the breaking change if it's the best option.

pub fn new(tracer: T) -> Self {
OpenTelemetryLayer {
tracer,
sampler: Box::new(sampler),
id_generator: sdk::IdGenerator::default(),
get_context: WithContext(Self::get_context),
_registry: marker::PhantomData,
}
Expand Down Expand Up @@ -343,52 +279,15 @@ where
/// ```
pub fn with_tracer<Tracer>(self, tracer: Tracer) -> OpenTelemetryLayer<S, Tracer>
where
Tracer: api::Tracer + 'static,
Tracer: api::Tracer + PreSampledTracer + '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: sdk::ShouldSample + '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.
Expand All @@ -407,14 +306,14 @@ where
let mut extensions = span.extensions_mut();
extensions
.get_mut::<api::SpanBuilder>()
.map(|builder| build_span_context(builder, self.sampler.as_ref()))
.map(|builder| self.tracer.sampled_span_context(builder))
// 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()))
.map(|builder| self.tracer.sampled_span_context(builder))
})
// Explicit root spans should have no parent context.
} else {
Expand All @@ -425,7 +324,7 @@ where
fn get_context(
dispatch: &tracing::Dispatch,
id: &span::Id,
f: &mut dyn FnMut(&mut api::SpanBuilder, &dyn sdk::ShouldSample),
f: &mut dyn FnMut(&mut api::SpanBuilder, &dyn PreSampledTracer),
) {
let subscriber = dispatch
.downcast_ref::<S>()
Expand All @@ -439,15 +338,15 @@ where

let mut extensions = span.extensions_mut();
if let Some(builder) = extensions.get_mut::<api::SpanBuilder>() {
f(builder, layer.sampler.as_ref());
f(builder, &layer.tracer);
}
}
}

impl<S, T> Layer<S> for OpenTelemetryLayer<S, T>
where
S: Subscriber + for<'span> LookupSpan<'span>,
T: api::Tracer + 'static,
T: api::Tracer + PreSampledTracer + 'static,
{
/// Creates an [OpenTelemetry `Span`] for the corresponding [tracing `Span`].
///
Expand All @@ -462,7 +361,7 @@ where
.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());
.with_span_id(self.tracer.new_span_id());

// Set optional parent span context from attrs
builder.parent_context = self.parent_span_context(attrs, &ctx);
Expand All @@ -473,7 +372,7 @@ where
if existing_otel_span_context.is_valid() {
builder.trace_id = Some(existing_otel_span_context.trace_id());
} else {
builder.trace_id = Some(self.id_generator.new_trace_id());
builder.trace_id = Some(self.tracer.new_trace_id());
}
}

Expand Down Expand Up @@ -507,7 +406,7 @@ where
.get_mut::<api::SpanBuilder>()
.expect("Missing SpanBuilder span extensions");

let follows_context = build_span_context(follows_builder, self.sampler.as_ref());
let follows_context = self.tracer.sampled_span_context(follows_builder);
let follows_link = api::Link::new(follows_context, Vec::new());
if let Some(ref mut links) = builder.links {
links.push(follows_link);
Expand Down Expand Up @@ -613,6 +512,18 @@ mod tests {
}
}

impl PreSampledTracer for TestTracer {
fn sampled_span_context(&self, _builder: &mut api::SpanBuilder) -> api::SpanContext {
api::SpanContext::empty_context()
}
fn new_trace_id(&self) -> api::TraceId {
api::TraceId::invalid()
}
fn new_span_id(&self) -> api::SpanId {
api::SpanId::invalid()
}
}

#[derive(Debug, Clone)]
struct TestSpan(api::SpanContext);
impl api::Span for TestSpan {
Expand Down
5 changes: 4 additions & 1 deletion tracing-opentelemetry/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,7 @@
//! may still occur on the path to 1.0. You can follow the changes via the
//! [spec repository] to track progress toward stabilization.
//!
//! [spec repository]: (https://github.com/open-telemetry/opentelemetry-specification)
//! [spec repository]: https://github.com/open-telemetry/opentelemetry-specification
//!
//! ## Examples
//!
Expand Down Expand Up @@ -100,6 +100,9 @@
mod layer;
/// Span extension which enables OpenTelemetry context management.
mod span_ext;
/// Protocols for OpenTelemetry Tracers that are compatible with Tracing
mod tracer;

pub use layer::{layer, OpenTelemetryLayer};
pub use span_ext::OpenTelemetrySpanExt;
pub use tracer::PreSampledTracer;
8 changes: 4 additions & 4 deletions tracing-opentelemetry/src/span_ext.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
use crate::layer::{build_span_context, WithContext};
use crate::layer::WithContext;
use opentelemetry::api;
use opentelemetry::api::TraceContextExt;

Expand Down Expand Up @@ -76,7 +76,7 @@ impl OpenTelemetrySpanExt for tracing::Span {
fn set_parent(&self, parent_context: &api::Context) {
self.with_subscriber(move |(id, subscriber)| {
if let Some(get_context) = subscriber.downcast_ref::<WithContext>() {
get_context.with_context(subscriber, id, move |builder, _sampler| {
get_context.with_context(subscriber, id, move |builder, _tracer| {
builder.parent_context = parent_context.remote_span_context().cloned()
});
}
Expand All @@ -87,8 +87,8 @@ impl OpenTelemetrySpanExt for tracing::Span {
let mut span_context = None;
self.with_subscriber(|(id, subscriber)| {
if let Some(get_context) = subscriber.downcast_ref::<WithContext>() {
get_context.with_context(subscriber, id, |builder, sampler| {
span_context = Some(build_span_context(builder, sampler));
get_context.with_context(subscriber, id, |builder, tracer| {
span_context = Some(tracer.sampled_span_context(builder));
})
}
});
Expand Down
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