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Trace requests through distributed and serverless apps on AWS.
Tokio Tracing
Structured, event-based diagnostics for Rust applications and libraries
tracing provides a flexible framework for instrumenting Rust code with structured, event‑level diagnostics, enabling logging, span tracking, and log integration.
Overview
Overview
tracing is a Rust library that lets developers instrument their programs with structured, event‑based diagnostics. By using macros such as info!, debug!, and the #[tracing::instrument] attribute, code can emit rich events and enter spans that automatically capture function arguments and execution context. The crate is runtime‑agnostic, so it works with any executor, not only Tokio.
Capabilities and Deployment
A Subscriber consumes the emitted data; the companion tracing-subscriber crate provides ready‑made implementations, including a formatter that writes human‑readable logs to stdout and a bridge that forwards traditional log records into the tracing system. Developers can build custom subscribers to send data to tracing back‑ends, metrics systems, or distributed tracing services. Integration is as simple as adding tracing = "0.1" and tracing-subscriber = "0.3" to Cargo.toml and initializing a subscriber at program start. Because the macros compile away when disabled, the overhead is minimal in production builds.
Highlights
Macro‑based instrumentation for events and spans
Subscriber model allowing custom data collection
Compatibility layer for the `log` crate
Fine‑grained level filtering and runtime configurability
Pros
- Zero‑cost abstractions when disabled
- Rich, structured data enables advanced analysis
- Works with any async runtime, not limited to Tokio
- Extensible via custom subscribers
Considerations
- Steeper learning curve than simple `log`
- Requires explicit subscriber setup to capture data
- Macro usage can increase compile times
- Structured output may need additional tooling to visualize
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Fit guide
Great for
- Developers needing detailed tracing across async boundaries
- Libraries that want to expose instrumentation without dictating logging
- Systems requiring correlation of events via spans
- Projects migrating from `log` to structured diagnostics
Not ideal when
- Simple scripts where lightweight `log` suffices
- Environments without Rust compile support
- Applications that cannot afford additional binary size
- Teams unwilling to adopt macro‑based instrumentation
How teams use it
Async request handling
Correlate inbound request spans with downstream service calls for end‑to‑end latency analysis.
Library diagnostics
Expose detailed events that downstream applications can filter or route to custom sinks.
Performance profiling
Collect fine‑grained trace data to identify hot paths and bottlenecks.
Log aggregation migration
Bridge existing `log` statements into structured traces without code changes.
Tech snapshot
Rust100%
Shell1%
Frequently asked questions
Do I need Tokio to use tracing?
No, tracing is runtime‑agnostic and works with any executor.
How does tracing differ from the `log` crate?
Tracing provides structured fields, spans, and hierarchical context, whereas `log` only supports flat messages.
Can I use tracing with existing `log`‑based libraries?
Yes, tracing-subscriber can consume `log` events and forward them into the tracing system.
What is a Subscriber?
A component that receives events and spans, deciding how to record or display them.
Is there a default subscriber?
tracing-subscriber::fmt::init() installs a simple stdout formatter based on the RUST_LOG environment variable.
Project at a glance
Active- Stars
- 6,464
- Watchers
- 6,464
- Forks
- 863
LicenseMIT
Repo age7 years old
Last commit3 weeks ago
Primary languageRust
Last synced 3 hours ago