3 releases (breaking)

Uses old Rust 2015

0.2.0 Apr 21, 2019
0.1.0 Mar 13, 2019
0.0.0 Nov 1, 2018

#36 in #subscriber

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4,397 downloads per month
Used in tokio-trace

MIT license

1.5K SLoC


Core primitives for tokio-trace.



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:

  • Span 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 and Callsite provide information describing Spans.

  • Field, FieldSet, Value, and ValueSet represent the structured data attached to a Span.

  • Dispatch allows span events to be dispatched to Subscribers.

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.


This project is licensed under the MIT license.


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.