bdbaf80073It is not uncommon that users who are new to tracing look at the examples in the `master` branch of the repository and find that they don't compile. This is because they are examples which compile with the code from the master branch, which is for the as yet unreleased tracing 0.2.0 ecosystem. Users should instead go to the `v0.1.x` branch to find examples compatible with the crates published on crates.io. This change adds a doc-comment to the beginning of every example file informing the user of this fact and suggesting that they check out the `v0.1.x` branch instead.
55 lines
1.8 KiB
Rust
55 lines
1.8 KiB
Rust
//! NOTE: This is pre-release documentation for the upcoming tracing 0.2.0 ecosystem. For the
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//! release examples, please see the `v0.1.x` branch instead.
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//!
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//! This example demonstrates overriding the way `tracing-subscriber`'s
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//! `FmtSubscriber` formats fields on spans and events, using a closure.
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//!
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//! We'll create a custom format that prints key-value pairs separated by
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//! colons rather than equals signs, and separates fields with commas.
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//!
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//! For an event like
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//! ```rust
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//! tracing::info!(hello = "world", answer = 42);
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//! ```
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//!
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//! the default formatter will format the fields like this:
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//! ```not_rust
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//! hello="world" answer=42
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//! ```
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//! while our custom formatter will output
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//! ```not_rust
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//! hello: "world", answer: 42
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//! ```
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#![deny(rust_2018_idioms)]
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#[path = "fmt/yak_shave.rs"]
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mod yak_shave;
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fn main() {
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use tracing_subscriber::{fmt::format, prelude::*};
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// Format fields using the provided closure.
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let format = format::debug_fn(|writer, field, value| {
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// We'll format the field name and value separated with a colon.
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write!(writer, "{}: {:?}", field, value)
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})
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// Separate each field with a comma.
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// This method is provided by an extension trait in the
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// `tracing-subscriber` prelude.
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.delimited(", ");
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// Create a `fmt` subscriber that uses our custom event format, and set it
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// as the default.
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tracing_subscriber::fmt().fmt_fields(format).init();
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// Shave some yaks!
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let number_of_yaks = 3;
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// this creates a new event, outside of any spans.
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tracing::info!(number_of_yaks, "preparing to shave yaks");
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let number_shaved = yak_shave::shave_all(number_of_yaks);
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tracing::info!(
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all_yaks_shaved = number_shaved == number_of_yaks,
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"yak shaving completed."
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);
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}
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