Utilities for implementing and composing
tracing is a framework for instrumenting Rust programs to collect
scoped, structured, and async-aware diagnostics. The
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
tracing-subscriber is intended for use by both
Subscriber authors and
application authors using
tracing to instrument their applications.
Compiler support: requires
The most important component of the
tracing-subscriber API is the
Layer trait, which provides a composable abstraction for building
Subscribers. Like the
Subscriber trait, a
Layer defines a
particular behavior for collecting trace data. Unlike
which implement a complete strategy for how trace data is collected,
Layers provide modular implementations of specific behaviors.
Therefore, they can be composed together to form a
Subscriber which is
capable of recording traces in a variety of ways. See the
documentation for details on using
In addition, the
Filter trait defines an interface for filtering what
spans and events are recorded by a particular layer. This allows different
Layers to handle separate subsets of the trace data emitted by a
program. See the documentation on per-layer filtering for more
information on using
Subscribers are provided for application authors:
fmt- Formats and logs tracing data (requires the
env-filter: Enables the
EnvFiltertype, which implements filtering similar to the
env_loggercrate. Enabled by default.
fmt: Enables the
fmtmodule, which provides a subscriber implementation for printing formatted representations of trace events. Enabled by default.
fmtsupport for ANSI terminal colors. Enabled by default.
registry: enables the
registrymodule. Enabled by default.
fmtsupport for JSON output. In JSON output, the ANSI feature does nothing.
tracing-log: Enables better formatting for events emitted by
logmacros in the
fmtsubscriber. On by default.
chrono: Enables human-readable time formatting in the
fmtsubscriber. Enabled by default.
smallvec: Causes the
EnvFiltertype to use the
smallveccrate (rather than
Vec) as a performance optimization. Enabled by default.
parking_lot: Use the
RwLockimplementation rather than the Rust standard library’s implementation.
Supported Rust Versions
Tracing is built against the latest stable release. The minimum supported version is 1.42. 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.
pub use layer::Layer;
pub use fmt::Subscriber as FmtSubscriber;
pub use fmt::fmt;
Utilities for working with fields and field visitors.
Layers that control which spans and events are enabled by the wrapped
Subscriber for formatting and logging
Layer trait, a composable abstraction for building
Storage for span data shared by multiple
Wrapper for a
Layer to allow it to be dynamically reloaded.
Extension traits and other utilities to make working with subscribers more ergonomic.
Tracks the currently executing span on a per-thread basis.
Layer which filters spans and events based on a set of filter
A shared, reusable store for spans.