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In the upstream `opentelemetry` crate, the `trace` and `metrics` features are gated by separate feature flags. This allows users who are only using OpenTelemetry for tracing, or who are only using it for metrics, to pick and choose what they depend on. Currently, the release version of `tracing-opentelemetry` only provides tracing functionality, and therefore, it only depends on `opentelemetry` with the `trace` feature enabled. However, the metrics support added in #2185 adds a dependency on the `opentelemetry/metrics` feature. This is currently always enabled. We should probably follow the same approach as upstream `opentelemetry`, and allow enabling/disabling metrics and tracing separately. This branch adds a `metrics` feature to `tracing-opentelemetry`, and makes the `MetricsLayer` from #2185 gated on the `metrics` feature. This feature flag is on by default, like the upstream `opentelemetry/metrics` feature, but it can be disabled using `default-features = false`. We should probably do something similar for the tracing components of the crate, and make them gated on a `trace` feature flag, but adding a feature flag to released APIs is not semver-compatible, so we should save that until the next breaking release.
Tracing OpenTelemetry
Utilities for adding OpenTelemetry interoperability to tracing.
Overview
tracing is a framework for instrumenting Rust programs to collect
structured, event-based diagnostic information. This crate provides a
subscriber that connects spans from multiple systems into a trace and
emits them to OpenTelemetry-compatible distributed tracing systems
for processing and visualization.
The crate provides the following types:
OpenTelemetryLayeradds OpenTelemetry context to alltracingspans.OpenTelemetrySpanExtallows OpenTelemetry parent trace information to be injected and extracted from atracingspan.
Compiler support: requires rustc 1.49+
Examples
Basic Usage
use opentelemetry::sdk::export::trace::stdout;
use tracing::{error, span};
use tracing_subscriber::layer::SubscriberExt;
use tracing_subscriber::Registry;
fn main() {
// Install a new OpenTelemetry trace pipeline
let tracer = stdout::new_pipeline().install_simple();
// Create a tracing layer with the configured tracer
let telemetry = tracing_opentelemetry::layer().with_tracer(tracer);
// Use the tracing subscriber `Registry`, or any other subscriber
// that impls `LookupSpan`
let subscriber = Registry::default().with(telemetry);
// Trace executed code
tracing::subscriber::with_default(subscriber, || {
// Spans will be sent to the configured OpenTelemetry exporter
let root = span!(tracing::Level::TRACE, "app_start", work_units = 2);
let _enter = root.enter();
error!("This event will be logged in the root span.");
});
}
Visualization example
# Run a supported collector like jaeger in the background
$ docker run -d -p6831:6831/udp -p6832:6832/udp -p16686:16686 jaegertracing/all-in-one:latest
# Run example to produce spans (from parent examples directory)
$ cargo run --example opentelemetry
# View spans (see the image below)
$ firefox http://localhost:16686/
Feature Flags
metrics: Enables the [MetricsSubscriber] type, a [subscriber] that exports OpenTelemetry metrics from specifically-named events. This enables themetricsfeature flag on theopentelemetrycrate.
Supported Rust Versions
Tracing Opentelemetry is built against the latest stable release. The minimum supported version is 1.46. The current Tracing version is not guaranteed to build on Rust versions earlier than the minimum supported version.
Tracing follows the same compiler support policies as the rest of the Tokio project. The current stable Rust compiler and the three most recent minor versions before it will always be supported. For example, if the current stable compiler version is 1.45, the minimum supported version will not be increased past 1.42, three minor versions prior. Increasing the minimum supported compiler version is not considered a semver breaking change as long as doing so complies with this policy.
License
This project is licensed under the MIT license.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Tracing by you, shall be licensed as MIT, without any additional terms or conditions.