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//! Utilities for implementing and composing [`tracing`] subscribers. //! //! [`tracing`] is a framework for instrumenting Rust programs to collect //! scoped, structured, and async-aware diagnostics. The [`Subscriber`] trait //! represents the functionality necessary to collect this trace data. This //! crate contains tools for composing subscribers out of smaller units of //! behaviour, and batteries-included implementations of common subscriber //! functionality. //! //! `tracing-subscriber` is intended for use by both `Subscriber` authors and //! application authors using `tracing` to instrument their applications. //! //! ## Included Subscribers //! //! The following `Subscriber`s are provided for application authors: //! //! - [`fmt`] - Formats and logs tracing data (requires the `fmt` feature flag) //! //! ## Feature Flags //! //! - `env-filter`: Enables the [`EnvFilter`] type, which implements filtering //! similar to the [`env_logger` crate]. Enabled by default. //! - `filter`: Alias for `env-filter`. This feature flag was renamed in version //! 0.1.2, and will be removed in version 0.2. //! - `fmt`: Enables the [`fmt`] module, which provides a subscriber //! implementation for printing formatted representations of trace events. //! Enabled by default. //! - `ansi`: Enables `fmt` support for ANSI terminal colors. Enabled by //! default. //! - `registry`: enables the experimental [`registry`] module. //! - `json`: Enables `fmt` support for JSON output. In JSON output, the ANSI feature does nothing. //! //! ### Optional Dependencies //! //! - [`tracing-log`]: Enables better formatting for events emitted by `log` //! macros in the `fmt` subscriber. On by default. //! - [`chrono`]: Enables human-readable time formatting in the `fmt` subscriber. //! Enabled by default. //! - [`smallvec`]: Causes the `EnvFilter` type to use the `smallvec` crate (rather //! than `Vec`) as a performance optimization. Enabled by default. //! - [`parking_lot`]: Use the `parking_lot` crate's `RwLock` implementation //! rather than the Rust standard library's implementation. //! //! [`tracing`]: https://docs.rs/tracing/latest/tracing/ //! [`Subscriber`]: https://docs.rs/tracing-core/latest/tracing_core/subscriber/trait.Subscriber.html //! [`EnvFilter`]: filter/struct.EnvFilter.html //! [`fmt`]: fmt/index.html //! [`tracing-log`]: https://crates.io/crates/tracing-log //! [`smallvec`]: https://crates.io/crates/smallvec //! [`chrono`]: https://crates.io/crates/chrono //! [`env_logger` crate]: https://crates.io/crates/env_logger //! [`parking_lot`]: https://crates.io/crates/parking_lot //! [`registry`]: registry/index.html #![doc(html_root_url = "https://docs.rs/tracing-subscriber/0.2.0-alpha.6")] #![cfg_attr(docsrs, feature(doc_cfg))] #![warn( missing_debug_implementations, missing_docs, rust_2018_idioms, unreachable_pub, bad_style, const_err, dead_code, improper_ctypes, non_shorthand_field_patterns, no_mangle_generic_items, overflowing_literals, path_statements, patterns_in_fns_without_body, private_in_public, unconditional_recursion, unused, unused_allocation, unused_comparisons, unused_parens, while_true )] use tracing_core::span::Id; #[macro_use] macro_rules! try_lock { ($lock:expr) => { try_lock!($lock, else return) }; ($lock:expr, else $els:expr) => { match $lock { Ok(l) => l, Err(_err) if std::thread::panicking() => $els, Err(_err) => panic!("lock poisoned"), } }; } pub mod field; pub mod filter; #[cfg(feature = "fmt")] #[cfg_attr(docsrs, doc(cfg(feature = "fmt")))] pub mod fmt; pub mod layer; pub mod prelude; #[cfg(feature = "registry")] #[cfg_attr(docsrs, doc(cfg(feature = "registry")))] pub mod registry; pub mod reload; pub(crate) mod sync; pub(crate) mod thread; #[cfg(feature = "env-filter")] #[cfg_attr(docsrs, doc(cfg(feature = "env-filter")))] pub use filter::EnvFilter; pub use layer::Layer; #[cfg(feature = "registry")] #[cfg_attr(docsrs, doc(cfg(feature = "registry")))] pub use registry::Registry; #[cfg(feature = "fmt")] #[cfg_attr(docsrs, doc(cfg(feature = "fmt")))] pub use fmt::Subscriber as FmtSubscriber; use std::default::Default; /// Tracks the currently executing span on a per-thread basis. #[derive(Debug)] pub struct CurrentSpan { current: thread::Local<Vec<Id>>, } impl CurrentSpan { /// Returns a new `CurrentSpan`. pub fn new() -> Self { Self { current: thread::Local::new(), } } /// Returns the [`Id`](::Id) of the span in which the current thread is /// executing, or `None` if it is not inside of a span. pub fn id(&self) -> Option<Id> { self.current.with(|current| current.last().cloned())? } /// Records that the current thread has entered the span with the provided ID. pub fn enter(&self, span: Id) { self.current.with(|current| current.push(span)); } /// Records that the current thread has exited a span. pub fn exit(&self) { self.current.with(|current| { let _ = current.pop(); }); } } impl Default for CurrentSpan { fn default() -> Self { Self::new() } } mod sealed { pub trait Sealed<A = ()> {} }