
## Motivation PR #934 fixed a bug in the CI configuration where MSRV checks were not being run correctly. After this was fixed, it was necessary to bump the MSRV to 1.40.0, as the tests were no longer actually passing on 1.39, because some dependencies no longer support it. While updating the documentation to indicate that the new MSRV is 1.40, I noticed that the note on the MSRV was located inconsistently in the READMEs and `lib.rs` documentation of various crates, and missing entirely in some cases. Additionally, there have been some questions on what our MSRV _policies_ are, and whether MSRV bumps are considered breaking changes (see e.g. #936). ## Solution I've updated all the MSRV notes in the documentation and READMEs to indicate that the MSRV is 1.40. I've also ensured that the MSRV note is in the same place for every crate (at the end of the "Overview" section in the docs), and that it's formatted consistently. Furthermore, I added a new section to the READMEs and `lib.rs` docs explaining the current MSRV policy in some detail. Hopefully, this should answer questions like #936 in the future. The MSRV note in the overview section includes a link to the section with further details. Finally, while doing this, I noticed a couple of crates (`tracing-journald` and `tracing-serde`) were missing top-level `lib.rs` docs. Rather than just adding an MSRV note and nothing else, I went ahead and fixed this using documentation from those crate's READMEs. Signed-off-by: Eliza Weisman <eliza@buoyant.io>
tracing-core
Core primitives for application-level tracing.
Overview
tracing
is a framework for instrumenting Rust programs to collect
structured, event-based diagnostic information. This crate defines the core
primitives of tracing
.
The 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 and events. -
Field
,FieldSet
,Value
, andValueSet
represent the structured data attached to spans and events. -
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
1.40+
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.
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 = "0.1.14", default-features = false }
Note:
tracing-core
'sno_std
support requiresliballoc
.
Supported Rust Versions
Tracing is built against the latest stable release. The minimum supported version is 1.40. 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 Tokio by you, shall be licensed as MIT, without any additional terms or conditions.