e3d29ac4dd
## Motivation Currently, most crates in this repository have `examples` directories that contain demonstrations of how to use that crate. In many cases, these examples also use APIs from _other_ crates in this repository --- for example, the `tracing-subscriber` `FmtSubscriber` is used by many examples to format the output generated by instrumentation APIs, so that users can see the generated output. The disadvantage to this approach is that it requires crates in this repository to have dev-dependencies on each other. This is problematic for a few reasons: * It makes it easy to inadvertently create cyclic dependencies between `tracing` crates. * When building a crate that depends on a crate with dev-dependencies, those dev-dependencies are downloaded and compiled, despite not being linked into the dependent crate. This means that users depending on a tracing crate will pull in a larger dependency tree, since the dev-dependencies used by examples are also downloaded, although they are not required by the dependent. This makes the tracing crate appear to be a much larger dependency than it actually is, and can make users' build times slower. * Finally, it means that the examples are scattered throughout the repository. In some cases, the examples demonstrate the functionality of multiple crates, but only live in one crate's `examples` dir. This can hurt the discoverability of the examples, especially for new users. ## Solution This branch moves all the examples out of individual crates and into a new `examples` crate (which is otherwise empty and cannot be published to crates.io). The `examples` crate is part of the root `tracing` workspace, so it's still possible to `cargo run --example WHATEVER`. Similarly, `cargo test --all` will still build the examples. All dev-dependencies which were only required by examples and not tests have been removed, which has a drastic impact on the dependency footprint of some crates. Finally, I've added a README to the `examples` crate, listing the available examples and what functionality they demonstrate. Refs: #315, #308 Signed-off-by: Eliza Weisman <eliza@buoyant.io>
tracing-serde
An adapter for serializing tracing types using serde.
Overview
tracing-serde enables serializing tracing types using
serde. tracing is a framework for instrumenting Rust programs
to collect structured, event-based diagnostic information.
Traditional logging is based on human-readable text messages.
tracing gives us machine-readable structured diagnostic
information. This lets us interact with diagnostic data
programmatically. With tracing-serde, you can implement a
Subscriber to serialize your tracing types and make use of the
existing ecosystem of serde serializers to talk with distributed
tracing systems.
Serializing diagnostic information allows us to do more with our logged values. For instance, when working with logging data in JSON gives us pretty-print when we're debugging in development and you can emit JSON and tracing data to monitor your services in production.
The tracing crate provides the APIs necessary for instrumenting
libraries and applications to emit trace data.
Usage
First, add this to your Cargo.toml:
[dependencies]
tracing = "0.1"
tracing-serde = "0.1"
Next, add this to your crate:
#[macro_use]
extern crate tracing;
extern crate tracing_serde;
use tracing_serde::AsSerde;
Please read the tracing documentation
for more information on how to create trace data.
This crate provides the as_serde function, via the AsSerde trait,
which enables serializing the Attributes, Event, Id, Metadata,
and Record tracing values.
For the full example, please see the examples folder.
Implement a Subscriber to format the serialization of tracing
types how you'd like.
pub struct JsonSubscriber {
next_id: AtomicUsize, // you need to assign span IDs, so you need a counter
}
impl Subscriber for JsonSubscriber {
fn new_span(&self, attrs: &Attributes) -> Id {
let id = self.next_id.fetch_add(1, Ordering::Relaxed);
let id = Id::from_u64(id as u64);
let json = json!({
"new_span": {
"attributes": attrs.as_serde(),
"id": id.as_serde(),
}});
println!("{}", json);
id
}
// ...
}
After you implement your Subscriber, you can use your tracing
subscriber (JsonSubscriber in the above example) to record serialized
trace data.
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.