Crate tracing_subscriber

Utilities for implementing and composing tracing subscribers.

tracing is a framework for instrumenting Rust programs to collect scoped, structured, and async-aware diagnostics. The Subscriber trait represents the functionality necessary to collect this trace data. This crate contains tools for composing subscribers out of smaller units of behaviour, and batteries-included implementations of common subscriber functionality.

tracing-subscriber is intended for use by both Subscriber authors and application authors using tracing to instrument their applications.

Included Subscribers

The following Subscribers are provided for application authors:

• fmt - Formats and logs tracing data (requires the fmt feature flag)

Feature Flags

• env-filter: Enables the EnvFilter type, which implements filtering similar to the env_logger crate. Enabled by default.
• filter: Alias for env-filter. This feature flag was renamed in version 0.1.2, and will be removed in version 0.2.
• fmt: Enables the fmt module, which provides a subscriber implementation for printing formatted representations of trace events. Enabled by default.
• ansi: Enables fmt support for ANSI terminal colors. Enabled by default.
• registry: enables the experimental registry module.
• json: Enables fmt support for JSON output. In JSON output, the ANSI feature does nothing.

Optional Dependencies

• tracing-log: Enables better formatting for events emitted by log macros in the fmt subscriber. On by default.
• chrono: Enables human-readable time formatting in the fmt subscriber. Enabled by default.
• smallvec: Causes the EnvFilter type to use the smallvec crate (rather than Vec) as a performance optimization. Enabled by default.
• parking_lot: Use the parking_lot crate's RwLock implementation rather than the Rust standard library's implementation.

Re-exports

pub use layer::Layer;

pub use fmt::Subscriber as FmtSubscriber;

Modules

field	Utilities for working with fields and field visitors.
filter	Layers that control which spans and events are enabled by the wrapped subscriber.
fmt	feature="fmt" A Subscriber for formatting and logging tracing data.
layer	A composable abstraction for building Subscribers.
prelude	The tracing-subscriber prelude.
registry	Storage for span data shared by multiple Layers.
reload	Wrapper for a Layer to allow it to be dynamically reloaded.

Structs

CurrentSpan	Tracks the currently executing span on a per-thread basis.
EnvFilter	feature="env-filter" A Layer which filters spans and events based on a set of filter directives.
Registry	feature="registry" A shared, reusable store for spans.