Eliza Weisman
d8177f81ac
## Motivation `tokio-trace` currently offers a strategy for compatibility with the `log` crate: its macros can be dropped in as a replacement for `log`'s macros, and a subscriber can be used that translates trace events to log records. However, this requires the application to be aware of `tokio-trace` and manually set up this subscriber. Many libraries currently emit `log` records, and would like to be able to emit `tokio-trace` instrumentation instead. The `tokio` runtimes are one such example. However, with the current log compatibility strategy, replacing existing logging with trace instrumentation would break `tokio`'s logs for any downstream user which is using only `log` and not `tokio-trace`. It is desirable for libraries to have the option to emit both `log` _and_ `tokio-trace` diagnostics from the same instrumentation points. ## Solution This branch adds a `log` feature flag to the `tokio-trace` crate, which when set, causes `tokio-trace` instrumentation to emit log records as well as `tokio-trace` instrumentation. ## Notes In order to allow spans to log their names when they are entered and exited even when the span is disabled, this branch adds an `&'static Metadata` to the `Span` type. This was previously stored in the `Inner` type and was thus only present when the span was enabled. This makes disabled spans one word longer, but enabled spans remain the same size. Fixes: #949 Signed-off-by: Eliza Weisman <[email protected]>
tokio-trace-core
Core primitives for tokio-trace.
Overview
tokio-trace is a framework for instrumenting Rust programs to collect
structured, event-based diagnostic information. This crate defines the core
primitives of tokio-trace.
The crate provides:
-
Spanidentifies a span within the execution of a program. -
Eventrepresents a single event within a trace. -
Subscriber, the trait implemented to collect trace data. -
Field,FieldSet,Value, andValueSetrepresent the structured data attached to aSpan. -
Dispatchallows span events to be dispatched toSubscribers.
In addition, it defines the global callsite registry and per-thread current dispatcher which other components of the tracing system rely on.
Application authors will typically not use this crate directly. Instead, they
will use the tokio-trace 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.
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.