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.
58 lines
2.4 KiB
Rust
58 lines
2.4 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 how `tracing` events can be recorded from within a
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//! panic hook, capturing the span context in which the program panicked.
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//!
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//! A custom panic hook can also be used to record panics that are captured
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//! using `catch_unwind`, such as when Tokio catches panics in spawned async
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//! tasks. See the `tokio_panic_hook.rs` example for an example of this.
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fn main() {
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let collector = tracing_subscriber::fmt()
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.with_max_level(tracing::Level::TRACE)
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.finish();
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// NOTE: Using `tracing` in a panic hook requires the use of the *global*
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// trace dispatcher (`tracing::collect::set_global_default`), rather than
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// the per-thread scoped dispatcher
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// (`tracing::collect::with_default`/`set_default`). With the scoped trace
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// dispatcher, the collector's thread-local context may already have been
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// torn down by unwinding by the time the panic handler is reached.
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tracing::collect::set_global_default(collector).unwrap();
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// Set a panic hook that records the panic as a `tracing` event at the
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// `ERROR` verbosity level.
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//
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// If we are currently in a span when the panic occurred, the logged event
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// will include the current span, allowing the context in which the panic
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// occurred to be recorded.
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std::panic::set_hook(Box::new(|panic| {
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// If the panic has a source location, record it as structured fields.
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if let Some(location) = panic.location() {
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// On nightly Rust, where the `PanicInfo` type also exposes a
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// `message()` method returning just the message, we could record
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// just the message instead of the entire `fmt::Display`
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// implementation, avoiding the duplicated location
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tracing::error!(
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message = %panic,
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panic.file = location.file(),
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panic.line = location.line(),
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panic.column = location.column(),
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);
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} else {
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tracing::error!(message = %panic);
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}
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}));
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for i in 0..10 {
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check_number(i);
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}
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}
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#[tracing::instrument]
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fn check_number(x: i32) {
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if x % 2 == 0 {
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panic!("I don't work with even numbers!");
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}
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}
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