Crate tracing_core
source ·Expand description
Core primitives for tracing
.
tracing
is a framework for instrumenting Rust programs to collect
structured, event-based diagnostic information. This crate defines the core
primitives of tracing
.
This crate provides:
-
span::Id
identifies a span within the execution of a program. -
Event
represents a single event within a trace. -
Subscriber
, the trait implemented to collect trace data. -
Metadata
andCallsite
provide information describing spans andEvent
s. -
Field
,FieldSet
,Value
, andValueSet
represent the structured data attached to a span. -
Dispatch
allows spans and events to be dispatched toSubscriber
s.
In addition, it defines the global callsite registry and per-thread current dispatcher which other components of the tracing system rely on.
Compiler support: requires rustc
1.56+
§Usage
Application authors will typically not use this crate directly. Instead,
they will use the tracing
crate, which provides a much more
fully-featured API. However, this crate’s API will change very infrequently,
so it may be used when dependencies must be very stable.
Subscriber
implementations may depend on tracing-core
rather than
tracing
, as the additional APIs provided by tracing
are primarily useful
for instrumenting libraries and applications, and are generally not
necessary for Subscriber
implementations.
The tokio-rs/tracing
repository contains less stable crates designed to
be used with the tracing
ecosystem. It includes a collection of
Subscriber
implementations, as well as utility and adapter crates.
§Crate Feature Flags
The following crate feature flags are available:
-
std
: Depend on the Rust standard library (enabled by default).no_std
users may disable this feature withdefault-features = false
:[dependencies] tracing-core = { version = "0.1.22", default-features = false }
Note:
tracing-core
’sno_std
support requiresliballoc
.
§Unstable Features
These feature flags enable unstable features. The public API may break in 0.1.x
releases. To enable these features, the --cfg tracing_unstable
must be passed to
rustc
when compiling.
The following unstable feature flags are currently available:
valuable
: Enables support for recording field values using thevaluable
crate.
§Enabling Unstable Features
The easiest way to set the tracing_unstable
cfg is to use the RUSTFLAGS
env variable when running cargo
commands:
RUSTFLAGS="--cfg tracing_unstable" cargo build
Alternatively, the following can be added to the .cargo/config
file in a
project to automatically enable the cfg flag for that project:
[build]
rustflags = ["--cfg", "tracing_unstable"]
§Supported Rust Versions
Tracing is built against the latest stable release. The minimum supported version is 1.56. 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 1.69, the minimum supported version will not be increased past 1.66, 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.
Re-exports§
Modules§
- Callsites represent the source locations from which spans or events originate.
- Dispatches trace events to
Subscriber
s. - Events represent single points in time during the execution of a program.
Span
andEvent
key-value data.- Metadata describing trace data.
- Spans represent periods of time in the execution of a program.
- Collectors collect and record trace data.
Macros§
- Statically constructs an
Identifier
for the providedCallsite
. - Statically constructs new span metadata.
Structs§
Dispatch
trace data to aSubscriber
.Event
s represent single points in time where something occurred during the execution of a program.- An opaque key allowing O(1) access to a field in a
Span
’s key-value data. - Describes the level of verbosity of a span or event.
- A filter comparable to a verbosity
Level
. - A low-level synchronization primitive for one-time global execution.
Traits§
- Trait implemented by callsites.
- Trait representing the functions required to collect trace data.