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| <span id="1086">1086</span> |
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| <span id="1090">1090</span> |
| <span id="1091">1091</span> |
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| <span id="1100">1100</span> |
| <span id="1101">1101</span> |
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| <span id="1103">1103</span> |
| <span id="1104">1104</span> |
| <span id="1105">1105</span> |
| <span id="1106">1106</span> |
| <span id="1107">1107</span> |
| <span id="1108">1108</span> |
| <span id="1109">1109</span> |
| <span id="1110">1110</span> |
| <span id="1111">1111</span> |
| <span id="1112">1112</span> |
| <span id="1113">1113</span> |
| <span id="1114">1114</span> |
| <span id="1115">1115</span> |
| </pre><pre class="rust"><code><span class="doccomment">//! A scoped, structured logging and diagnostics system. |
| //! |
| //! # Overview |
| //! |
| //! `tracing` is a framework for instrumenting Rust programs to collect |
| //! structured, event-based diagnostic information. |
| //! |
| //! In asynchronous systems like Tokio, interpreting traditional log messages can |
| //! often be quite challenging. Since individual tasks are multiplexed on the same |
| //! thread, associated events and log lines are intermixed making it difficult to |
| //! trace the logic flow. `tracing` expands upon logging-style diagnostics by |
| //! allowing libraries and applications to record structured events with additional |
| //! information about *temporality* and *causality* — unlike a log message, a span |
| //! in `tracing` has a beginning and end time, may be entered and exited by the |
| //! flow of execution, and may exist within a nested tree of similar spans. In |
| //! addition, `tracing` spans are *structured*, with the ability to record typed |
| //! data as well as textual messages. |
| //! |
| //! The `tracing` crate provides the APIs necessary for instrumenting libraries |
| //! and applications to emit trace data. |
| //! |
| //! *Compiler support: [requires `rustc` 1.49+][msrv]* |
| //! |
| //! [msrv]: #supported-rust-versions |
| //! # Core Concepts |
| //! |
| //! The core of `tracing`'s API is composed of _spans_, _events_ and |
| //! _subscribers_. We'll cover these in turn. |
| //! |
| //! ## Spans |
| //! |
| //! To record the flow of execution through a program, `tracing` introduces the |
| //! concept of [spans]. Unlike a log line that represents a _moment in |
| //! time_, a span represents a _period of time_ with a beginning and an end. When a |
| //! program begins executing in a context or performing a unit of work, it |
| //! _enters_ that context's span, and when it stops executing in that context, |
| //! it _exits_ the span. The span in which a thread is currently executing is |
| //! referred to as that thread's _current_ span. |
| //! |
| //! For example: |
| //! ``` |
| //! use tracing::{span, Level}; |
| //! # fn main() { |
| //! let span = span!(Level::TRACE, "my_span"); |
| //! // `enter` returns a RAII guard which, when dropped, exits the span. this |
| //! // indicates that we are in the span for the current lexical scope. |
| //! let _enter = span.enter(); |
| //! // perform some work in the context of `my_span`... |
| //! # } |
| //!``` |
| //! |
| //! The [`span` module][span]'s documentation provides further details on how to |
| //! use spans. |
| //! |
| //! <div class="example-wrap" style="display:inline-block"><pre class="compile_fail" style="white-space:normal;font:inherit;"> |
| //! |
| //! **Warning**: In asynchronous code that uses async/await syntax, |
| //! `Span::enter` may produce incorrect traces if the returned drop |
| //! guard is held across an await point. See |
| //! [the method documentation][Span#in-asynchronous-code] for details. |
| //! |
| //! </pre></div> |
| //! |
| //! ## Events |
| //! |
| //! An [`Event`] represents a _moment_ in time. It signifies something that |
| //! happened while a trace was being recorded. `Event`s are comparable to the log |
| //! records emitted by unstructured logging code, but unlike a typical log line, |
| //! an `Event` may occur within the context of a span. |
| //! |
| //! For example: |
| //! ``` |
| //! use tracing::{event, span, Level}; |
| //! |
| //! # fn main() { |
| //! // records an event outside of any span context: |
| //! event!(Level::INFO, "something happened"); |
| //! |
| //! let span = span!(Level::INFO, "my_span"); |
| //! let _guard = span.enter(); |
| //! |
| //! // records an event within "my_span". |
| //! event!(Level::DEBUG, "something happened inside my_span"); |
| //! # } |
| //!``` |
| //! |
| //! In general, events should be used to represent points in time _within_ a |
| //! span — a request returned with a given status code, _n_ new items were |
| //! taken from a queue, and so on. |
| //! |
| //! The [`Event` struct][`Event`] documentation provides further details on using |
| //! events. |
| //! |
| //! ## Subscribers |
| //! |
| //! As `Span`s and `Event`s occur, they are recorded or aggregated by |
| //! implementations of the [`Subscriber`] trait. `Subscriber`s are notified |
| //! when an `Event` takes place and when a `Span` is entered or exited. These |
| //! notifications are represented by the following `Subscriber` trait methods: |
| //! |
| //! + [`event`][Subscriber::event], called when an `Event` takes place, |
| //! + [`enter`], called when execution enters a `Span`, |
| //! + [`exit`], called when execution exits a `Span` |
| //! |
| //! In addition, subscribers may implement the [`enabled`] function to _filter_ |
| //! the notifications they receive based on [metadata] describing each `Span` |
| //! or `Event`. If a call to `Subscriber::enabled` returns `false` for a given |
| //! set of metadata, that `Subscriber` will *not* be notified about the |
| //! corresponding `Span` or `Event`. For performance reasons, if no currently |
| //! active subscribers express interest in a given set of metadata by returning |
| //! `true`, then the corresponding `Span` or `Event` will never be constructed. |
| //! |
| //! # Usage |
| //! |
| //! First, add this to your `Cargo.toml`: |
| //! |
| //! ```toml |
| //! [dependencies] |
| //! tracing = "0.1" |
| //! ``` |
| //! |
| //! ## Recording Spans and Events |
| //! |
| //! Spans and events are recorded using macros. |
| //! |
| //! ### Spans |
| //! |
| //! The [`span!`] macro expands to a [`Span` struct][`Span`] which is used to |
| //! record a span. The [`Span::enter`] method on that struct records that the |
| //! span has been entered, and returns a [RAII] guard object, which will exit |
| //! the span when dropped. |
| //! |
| //! For example: |
| //! |
| //! ```rust |
| //! use tracing::{span, Level}; |
| //! # fn main() { |
| //! // Construct a new span named "my span" with trace log level. |
| //! let span = span!(Level::TRACE, "my span"); |
| //! |
| //! // Enter the span, returning a guard object. |
| //! let _enter = span.enter(); |
| //! |
| //! // Any trace events that occur before the guard is dropped will occur |
| //! // within the span. |
| //! |
| //! // Dropping the guard will exit the span. |
| //! # } |
| //! ``` |
| //! |
| //! The [`#[instrument]`][instrument] attribute provides an easy way to |
| //! add `tracing` spans to functions. A function annotated with `#[instrument]` |
| //! will create and enter a span with that function's name every time the |
| //! function is called, with arguments to that function will be recorded as |
| //! fields using `fmt::Debug`. |
| //! |
| //! For example: |
| //! ```ignore |
| //! # // this doctest is ignored because we don't have a way to say |
| //! # // that it should only be run with cfg(feature = "attributes") |
| //! use tracing::{Level, event, instrument}; |
| //! |
| //! #[instrument] |
| //! pub fn my_function(my_arg: usize) { |
| //! // This event will be recorded inside a span named `my_function` with the |
| //! // field `my_arg`. |
| //! event!(Level::INFO, "inside my_function!"); |
| //! // ... |
| //! } |
| //! # fn main() {} |
| //! ``` |
| //! |
| //! For functions which don't have built-in tracing support and can't have |
| //! the `#[instrument]` attribute applied (such as from an external crate), |
| //! the [`Span` struct][`Span`] has a [`in_scope()` method][`in_scope`] |
| //! which can be used to easily wrap synchonous code in a span. |
| //! |
| //! For example: |
| //! ```rust |
| //! use tracing::info_span; |
| //! |
| //! # fn doc() -> Result<(), ()> { |
| //! # mod serde_json { |
| //! # pub(crate) fn from_slice(buf: &[u8]) -> Result<(), ()> { Ok(()) } |
| //! # } |
| //! # let buf: [u8; 0] = []; |
| //! let json = info_span!("json.parse").in_scope(|| serde_json::from_slice(&buf))?; |
| //! # let _ = json; // suppress unused variable warning |
| //! # Ok(()) |
| //! # } |
| //! ``` |
| //! |
| //! You can find more examples showing how to use this crate [here][examples]. |
| //! |
| //! [RAII]: https://github.com/rust-unofficial/patterns/blob/master/patterns/behavioural/RAII.md |
| //! [examples]: https://github.com/tokio-rs/tracing/tree/master/examples |
| //! |
| //! ### Events |
| //! |
| //! [`Event`]s are recorded using the [`event!`] macro: |
| //! |
| //! ```rust |
| //! # fn main() { |
| //! use tracing::{event, Level}; |
| //! event!(Level::INFO, "something has happened!"); |
| //! # } |
| //! ``` |
| //! |
| //! ## Using the Macros |
| //! |
| //! The [`span!`] and [`event!`] macros as well as the `#[instrument]` attribute |
| //! use fairly similar syntax, with some exceptions. |
| //! |
| //! ### Configuring Attributes |
| //! |
| //! Both macros require a [`Level`] specifying the verbosity of the span or |
| //! event. Optionally, the [target] and [parent span] may be overridden. If the |
| //! target and parent span are not overridden, they will default to the |
| //! module path where the macro was invoked and the current span (as determined |
| //! by the subscriber), respectively. |
| //! |
| //! For example: |
| //! |
| //! ``` |
| //! # use tracing::{span, event, Level}; |
| //! # fn main() { |
| //! span!(target: "app_spans", Level::TRACE, "my span"); |
| //! event!(target: "app_events", Level::INFO, "something has happened!"); |
| //! # } |
| //! ``` |
| //! ``` |
| //! # use tracing::{span, event, Level}; |
| //! # fn main() { |
| //! let span = span!(Level::TRACE, "my span"); |
| //! event!(parent: &span, Level::INFO, "something has happened!"); |
| //! # } |
| //! ``` |
| //! |
| //! The span macros also take a string literal after the level, to set the name |
| //! of the span. |
| //! |
| //! ### Recording Fields |
| //! |
| //! Structured fields on spans and events are specified using the syntax |
| //! `field_name = field_value`. Fields are separated by commas. |
| //! |
| //! ``` |
| //! # use tracing::{event, Level}; |
| //! # fn main() { |
| //! // records an event with two fields: |
| //! // - "answer", with the value 42 |
| //! // - "question", with the value "life, the universe and everything" |
| //! event!(Level::INFO, answer = 42, question = "life, the universe, and everything"); |
| //! # } |
| //! ``` |
| //! |
| //! As shorthand, local variables may be used as field values without an |
| //! assignment, similar to [struct initializers]. For example: |
| //! |
| //! ``` |
| //! # use tracing::{span, Level}; |
| //! # fn main() { |
| //! let user = "ferris"; |
| //! |
| //! span!(Level::TRACE, "login", user); |
| //! // is equivalent to: |
| //! span!(Level::TRACE, "login", user = user); |
| //! # } |
| //!``` |
| //! |
| //! Field names can include dots, but should not be terminated by them: |
| //! ``` |
| //! # use tracing::{span, Level}; |
| //! # fn main() { |
| //! let user = "ferris"; |
| //! let email = "ferris@rust-lang.org"; |
| //! span!(Level::TRACE, "login", user, user.email = email); |
| //! # } |
| //!``` |
| //! |
| //! Since field names can include dots, fields on local structs can be used |
| //! using the local variable shorthand: |
| //! ``` |
| //! # use tracing::{span, Level}; |
| //! # fn main() { |
| //! # struct User { |
| //! # name: &'static str, |
| //! # email: &'static str, |
| //! # } |
| //! let user = User { |
| //! name: "ferris", |
| //! email: "ferris@rust-lang.org", |
| //! }; |
| //! // the span will have the fields `user.name = "ferris"` and |
| //! // `user.email = "ferris@rust-lang.org"`. |
| //! span!(Level::TRACE, "login", user.name, user.email); |
| //! # } |
| //!``` |
| //! |
| //! Fields with names that are not Rust identifiers, or with names that are Rust reserved words, |
| //! may be created using quoted string literals. However, this may not be used with the local |
| //! variable shorthand. |
| //! ``` |
| //! # use tracing::{span, Level}; |
| //! # fn main() { |
| //! // records an event with fields whose names are not Rust identifiers |
| //! // - "guid:x-request-id", containing a `:`, with the value "abcdef" |
| //! // - "type", which is a reserved word, with the value "request" |
| //! span!(Level::TRACE, "api", "guid:x-request-id" = "abcdef", "type" = "request"); |
| //! # } |
| //!``` |
| //! |
| //! The `?` sigil is shorthand that specifies a field should be recorded using |
| //! its [`fmt::Debug`] implementation: |
| //! ``` |
| //! # use tracing::{event, Level}; |
| //! # fn main() { |
| //! #[derive(Debug)] |
| //! struct MyStruct { |
| //! field: &'static str, |
| //! } |
| //! |
| //! let my_struct = MyStruct { |
| //! field: "Hello world!" |
| //! }; |
| //! |
| //! // `my_struct` will be recorded using its `fmt::Debug` implementation. |
| //! event!(Level::TRACE, greeting = ?my_struct); |
| //! // is equivalent to: |
| //! event!(Level::TRACE, greeting = tracing::field::debug(&my_struct)); |
| //! # } |
| //! ``` |
| //! |
| //! The `%` sigil operates similarly, but indicates that the value should be |
| //! recorded using its [`fmt::Display`] implementation: |
| //! ``` |
| //! # use tracing::{event, Level}; |
| //! # fn main() { |
| //! # #[derive(Debug)] |
| //! # struct MyStruct { |
| //! # field: &'static str, |
| //! # } |
| //! # |
| //! # let my_struct = MyStruct { |
| //! # field: "Hello world!" |
| //! # }; |
| //! // `my_struct.field` will be recorded using its `fmt::Display` implementation. |
| //! event!(Level::TRACE, greeting = %my_struct.field); |
| //! // is equivalent to: |
| //! event!(Level::TRACE, greeting = tracing::field::display(&my_struct.field)); |
| //! # } |
| //! ``` |
| //! |
| //! The `%` and `?` sigils may also be used with local variable shorthand: |
| //! |
| //! ``` |
| //! # use tracing::{event, Level}; |
| //! # fn main() { |
| //! # #[derive(Debug)] |
| //! # struct MyStruct { |
| //! # field: &'static str, |
| //! # } |
| //! # |
| //! # let my_struct = MyStruct { |
| //! # field: "Hello world!" |
| //! # }; |
| //! // `my_struct.field` will be recorded using its `fmt::Display` implementation. |
| //! event!(Level::TRACE, %my_struct.field); |
| //! # } |
| //! ``` |
| //! |
| //! Additionally, a span may declare fields with the special value [`Empty`], |
| //! which indicates that that the value for that field does not currently exist |
| //! but may be recorded later. For example: |
| //! |
| //! ``` |
| //! use tracing::{trace_span, field}; |
| //! |
| //! // Create a span with two fields: `greeting`, with the value "hello world", and |
| //! // `parting`, without a value. |
| //! let span = trace_span!("my_span", greeting = "hello world", parting = field::Empty); |
| //! |
| //! // ... |
| //! |
| //! // Now, record a value for parting as well. |
| //! span.record("parting", &"goodbye world!"); |
| //! ``` |
| //! |
| //! Note that a span may have up to 32 fields. The following will not compile: |
| //! |
| //! ```rust,compile_fail |
| //! # use tracing::Level; |
| //! # fn main() { |
| //! let bad_span = span!( |
| //! Level::TRACE, |
| //! "too many fields!", |
| //! a = 1, b = 2, c = 3, d = 4, e = 5, f = 6, g = 7, h = 8, i = 9, |
| //! j = 10, k = 11, l = 12, m = 13, n = 14, o = 15, p = 16, q = 17, |
| //! r = 18, s = 19, t = 20, u = 21, v = 22, w = 23, x = 24, y = 25, |
| //! z = 26, aa = 27, bb = 28, cc = 29, dd = 30, ee = 31, ff = 32, gg = 33 |
| //! ); |
| //! # } |
| //! ``` |
| //! |
| //! Finally, events may also include human-readable messages, in the form of a |
| //! [format string][fmt] and (optional) arguments, **after** the event's |
| //! key-value fields. If a format string and arguments are provided, |
| //! they will implicitly create a new field named `message` whose value is the |
| //! provided set of format arguments. |
| //! |
| //! For example: |
| //! |
| //! ``` |
| //! # use tracing::{event, Level}; |
| //! # fn main() { |
| //! let question = "the ultimate question of life, the universe, and everything"; |
| //! let answer = 42; |
| //! // records an event with the following fields: |
| //! // - `question.answer` with the value 42, |
| //! // - `question.tricky` with the value `true`, |
| //! // - "message", with the value "the answer to the ultimate question of life, the |
| //! // universe, and everything is 42." |
| //! event!( |
| //! Level::DEBUG, |
| //! question.answer = answer, |
| //! question.tricky = true, |
| //! "the answer to {} is {}.", question, answer |
| //! ); |
| //! # } |
| //! ``` |
| //! |
| //! Specifying a formatted message in this manner does not allocate by default. |
| //! |
| //! [struct initializers]: https://doc.rust-lang.org/book/ch05-01-defining-structs.html#using-the-field-init-shorthand-when-variables-and-fields-have-the-same-name |
| //! [target]: Metadata::target |
| //! [parent span]: span::Attributes::parent |
| //! [determined contextually]: span::Attributes::is_contextual |
| //! [`fmt::Debug`]: std::fmt::Debug |
| //! [`fmt::Display`]: std::fmt::Display |
| //! [fmt]: std::fmt#usage |
| //! [`Empty`]: field::Empty |
| //! |
| //! ### Shorthand Macros |
| //! |
| //! `tracing` also offers a number of macros with preset verbosity levels. |
| //! The [`trace!`], [`debug!`], [`info!`], [`warn!`], and [`error!`] behave |
| //! similarly to the [`event!`] macro, but with the [`Level`] argument already |
| //! specified, while the corresponding [`trace_span!`], [`debug_span!`], |
| //! [`info_span!`], [`warn_span!`], and [`error_span!`] macros are the same, |
| //! but for the [`span!`] macro. |
| //! |
| //! These are intended both as a shorthand, and for compatibility with the [`log`] |
| //! crate (see the next section). |
| //! |
| //! [`span!`]: span! |
| //! [`event!`]: event! |
| //! [`trace!`]: trace! |
| //! [`debug!`]: debug! |
| //! [`info!`]: info! |
| //! [`warn!`]: warn! |
| //! [`error!`]: error! |
| //! [`trace_span!`]: trace_span! |
| //! [`debug_span!`]: debug_span! |
| //! [`info_span!`]: info_span! |
| //! [`warn_span!`]: warn_span! |
| //! [`error_span!`]: error_span! |
| //! |
| //! ### For `log` Users |
| //! |
| //! Users of the [`log`] crate should note that `tracing` exposes a set of |
| //! macros for creating `Event`s (`trace!`, `debug!`, `info!`, `warn!`, and |
| //! `error!`) which may be invoked with the same syntax as the similarly-named |
| //! macros from the `log` crate. Often, the process of converting a project to |
| //! use `tracing` can begin with a simple drop-in replacement. |
| //! |
| //! Let's consider the `log` crate's yak-shaving example: |
| //! |
| //! ```rust,ignore |
| //! use std::{error::Error, io}; |
| //! use tracing::{debug, error, info, span, warn, Level}; |
| //! |
| //! // the `#[tracing::instrument]` attribute creates and enters a span |
| //! // every time the instrumented function is called. The span is named after the |
| //! // the function or method. Parameters passed to the function are recorded as fields. |
| //! #[tracing::instrument] |
| //! pub fn shave(yak: usize) -> Result<(), Box<dyn Error + 'static>> { |
| //! // this creates an event at the DEBUG level with two fields: |
| //! // - `excitement`, with the key "excitement" and the value "yay!" |
| //! // - `message`, with the key "message" and the value "hello! I'm gonna shave a yak." |
| //! // |
| //! // unlike other fields, `message`'s shorthand initialization is just the string itself. |
| //! debug!(excitement = "yay!", "hello! I'm gonna shave a yak."); |
| //! if yak == 3 { |
| //! warn!("could not locate yak!"); |
| //! // note that this is intended to demonstrate `tracing`'s features, not idiomatic |
| //! // error handling! in a library or application, you should consider returning |
| //! // a dedicated `YakError`. libraries like snafu or thiserror make this easy. |
| //! return Err(io::Error::new(io::ErrorKind::Other, "shaving yak failed!").into()); |
| //! } else { |
| //! debug!("yak shaved successfully"); |
| //! } |
| //! Ok(()) |
| //! } |
| //! |
| //! pub fn shave_all(yaks: usize) -> usize { |
| //! // Constructs a new span named "shaving_yaks" at the TRACE level, |
| //! // and a field whose key is "yaks". This is equivalent to writing: |
| //! // |
| //! // let span = span!(Level::TRACE, "shaving_yaks", yaks = yaks); |
| //! // |
| //! // local variables (`yaks`) can be used as field values |
| //! // without an assignment, similar to struct initializers. |
| //! let _span = span!(Level::TRACE, "shaving_yaks", yaks).entered(); |
| //! |
| //! info!("shaving yaks"); |
| //! |
| //! let mut yaks_shaved = 0; |
| //! for yak in 1..=yaks { |
| //! let res = shave(yak); |
| //! debug!(yak, shaved = res.is_ok()); |
| //! |
| //! if let Err(ref error) = res { |
| //! // Like spans, events can also use the field initialization shorthand. |
| //! // In this instance, `yak` is the field being initalized. |
| //! error!(yak, error = error.as_ref(), "failed to shave yak!"); |
| //! } else { |
| //! yaks_shaved += 1; |
| //! } |
| //! debug!(yaks_shaved); |
| //! } |
| //! |
| //! yaks_shaved |
| //! } |
| //! ``` |
| //! |
| //! ## In libraries |
| //! |
| //! Libraries should link only to the `tracing` crate, and use the provided |
| //! macros to record whatever information will be useful to downstream |
| //! consumers. |
| //! |
| //! ## In executables |
| //! |
| //! In order to record trace events, executables have to use a `Subscriber` |
| //! implementation compatible with `tracing`. A `Subscriber` implements a |
| //! way of collecting trace data, such as by logging it to standard output. |
| //! |
| //! This library does not contain any `Subscriber` implementations; these are |
| //! provided by [other crates](#related-crates). |
| //! |
| //! The simplest way to use a subscriber is to call the [`set_global_default`] |
| //! function: |
| //! |
| //! ``` |
| //! extern crate tracing; |
| //! # pub struct FooSubscriber; |
| //! # use tracing::{span::{Id, Attributes, Record}, Metadata}; |
| //! # impl tracing::Subscriber for FooSubscriber { |
| //! # fn new_span(&self, _: &Attributes) -> Id { Id::from_u64(0) } |
| //! # fn record(&self, _: &Id, _: &Record) {} |
| //! # fn event(&self, _: &tracing::Event) {} |
| //! # fn record_follows_from(&self, _: &Id, _: &Id) {} |
| //! # fn enabled(&self, _: &Metadata) -> bool { false } |
| //! # fn enter(&self, _: &Id) {} |
| //! # fn exit(&self, _: &Id) {} |
| //! # } |
| //! # impl FooSubscriber { |
| //! # fn new() -> Self { FooSubscriber } |
| //! # } |
| //! # fn main() { |
| //! |
| //! let my_subscriber = FooSubscriber::new(); |
| //! tracing::subscriber::set_global_default(my_subscriber) |
| //! .expect("setting tracing default failed"); |
| //! # } |
| //! ``` |
| //! |
| //! <pre class="compile_fail" style="white-space:normal;font:inherit;"> |
| //! <strong>Warning</strong>: In general, libraries should <em>not</em> call |
| //! <code>set_global_default()</code>! Doing so will cause conflicts when |
| //! executables that depend on the library try to set the default later. |
| //! </pre> |
| //! |
| //! This subscriber will be used as the default in all threads for the |
| //! remainder of the duration of the program, similar to setting the logger |
| //! in the `log` crate. |
| //! |
| //! In addition, the default subscriber can be set through using the |
| //! [`with_default`] function. This follows the `tokio` pattern of using |
| //! closures to represent executing code in a context that is exited at the end |
| //! of the closure. For example: |
| //! |
| //! ```rust |
| //! # pub struct FooSubscriber; |
| //! # use tracing::{span::{Id, Attributes, Record}, Metadata}; |
| //! # impl tracing::Subscriber for FooSubscriber { |
| //! # fn new_span(&self, _: &Attributes) -> Id { Id::from_u64(0) } |
| //! # fn record(&self, _: &Id, _: &Record) {} |
| //! # fn event(&self, _: &tracing::Event) {} |
| //! # fn record_follows_from(&self, _: &Id, _: &Id) {} |
| //! # fn enabled(&self, _: &Metadata) -> bool { false } |
| //! # fn enter(&self, _: &Id) {} |
| //! # fn exit(&self, _: &Id) {} |
| //! # } |
| //! # impl FooSubscriber { |
| //! # fn new() -> Self { FooSubscriber } |
| //! # } |
| //! # fn main() { |
| //! |
| //! let my_subscriber = FooSubscriber::new(); |
| //! # #[cfg(feature = "std")] |
| //! tracing::subscriber::with_default(my_subscriber, || { |
| //! // Any trace events generated in this closure or by functions it calls |
| //! // will be collected by `my_subscriber`. |
| //! }) |
| //! # } |
| //! ``` |
| //! |
| //! This approach allows trace data to be collected by multiple subscribers |
| //! within different contexts in the program. Note that the override only applies to the |
| //! currently executing thread; other threads will not see the change from with_default. |
| //! |
| //! Any trace events generated outside the context of a subscriber will not be collected. |
| //! |
| //! Once a subscriber has been set, instrumentation points may be added to the |
| //! executable using the `tracing` crate's macros. |
| //! |
| //! ## `log` Compatibility |
| //! |
| //! The [`log`] crate provides a simple, lightweight logging facade for Rust. |
| //! While `tracing` builds upon `log`'s foundation with richer structured |
| //! diagnostic data, `log`'s simplicity and ubiquity make it the "lowest common |
| //! denominator" for text-based logging in Rust — a vast majority of Rust |
| //! libraries and applications either emit or consume `log` records. Therefore, |
| //! `tracing` provides multiple forms of interoperability with `log`: `tracing` |
| //! instrumentation can emit `log` records, and a compatibility layer enables |
| //! `tracing` [`Subscriber`]s to consume `log` records as `tracing` [`Event`]s. |
| //! |
| //! ### Emitting `log` Records |
| //! |
| //! This crate provides two feature flags, "log" and "log-always", which will |
| //! cause [spans] and [events] to emit `log` records. When the "log" feature is |
| //! enabled, if no `tracing` `Subscriber` is active, invoking an event macro or |
| //! creating a span with fields will emit a `log` record. This is intended |
| //! primarily for use in libraries which wish to emit diagnostics that can be |
| //! consumed by applications using `tracing` *or* `log`, without paying the |
| //! additional overhead of emitting both forms of diagnostics when `tracing` is |
| //! in use. |
| //! |
| //! Enabling the "log-always" feature will cause `log` records to be emitted |
| //! even if a `tracing` `Subscriber` _is_ set. This is intended to be used in |
| //! applications where a `log` `Logger` is being used to record a textual log, |
| //! and `tracing` is used only to record other forms of diagnostics (such as |
| //! metrics, profiling, or distributed tracing data). Unlike the "log" feature, |
| //! libraries generally should **not** enable the "log-always" feature, as doing |
| //! so will prevent applications from being able to opt out of the `log` records. |
| //! |
| //! See [here][flags] for more details on this crate's feature flags. |
| //! |
| //! The generated `log` records' messages will be a string representation of the |
| //! span or event's fields, and all additional information recorded by `log` |
| //! (target, verbosity level, module path, file, and line number) will also be |
| //! populated. Additionally, `log` records are also generated when spans are |
| //! entered, exited, and closed. Since these additional span lifecycle logs have |
| //! the potential to be very verbose, and don't include additional fields, they |
| //! will always be emitted at the `Trace` level, rather than inheriting the |
| //! level of the span that generated them. Furthermore, they are are categorized |
| //! under a separate `log` target, "tracing::span" (and its sub-target, |
| //! "tracing::span::active", for the logs on entering and exiting a span), which |
| //! may be enabled or disabled separately from other `log` records emitted by |
| //! `tracing`. |
| //! |
| //! ### Consuming `log` Records |
| //! |
| //! The [`tracing-log`] crate provides a compatibility layer which |
| //! allows a `tracing` [`Subscriber`] to consume `log` records as though they |
| //! were `tracing` [events]. This allows applications using `tracing` to record |
| //! the logs emitted by dependencies using `log` as events within the context of |
| //! the application's trace tree. See [that crate's documentation][log-tracer] |
| //! for details. |
| //! |
| //! [log-tracer]: https://docs.rs/tracing-log/latest/tracing_log/#convert-log-records-to-tracing-events |
| //! |
| //! ## Related Crates |
| //! |
| //! In addition to `tracing` and `tracing-core`, the [`tokio-rs/tracing`] repository |
| //! contains several additional crates designed to be used with the `tracing` ecosystem. |
| //! This includes a collection of `Subscriber` implementations, as well as utility |
| //! and adapter crates to assist in writing `Subscriber`s and instrumenting |
| //! applications. |
| //! |
| //! In particular, the following crates are likely to be of interest: |
| //! |
| //! - [`tracing-futures`] provides a compatibility layer with the `futures` |
| //! crate, allowing spans to be attached to `Future`s, `Stream`s, and `Executor`s. |
| //! - [`tracing-subscriber`] provides `Subscriber` implementations and |
| //! utilities for working with `Subscriber`s. This includes a [`FmtSubscriber`] |
| //! `FmtSubscriber` for logging formatted trace data to stdout, with similar |
| //! filtering and formatting to the [`env_logger`] crate. |
| //! - [`tracing-log`] provides a compatibility layer with the [`log`] crate, |
| //! allowing log messages to be recorded as `tracing` `Event`s within the |
| //! trace tree. This is useful when a project using `tracing` have |
| //! dependencies which use `log`. Note that if you're using |
| //! `tracing-subscriber`'s `FmtSubscriber`, you don't need to depend on |
| //! `tracing-log` directly. |
| //! - [`tracing-appender`] provides utilities for outputting tracing data, |
| //! including a file appender and non blocking writer. |
| //! |
| //! Additionally, there are also several third-party crates which are not |
| //! maintained by the `tokio` project. These include: |
| //! |
| //! - [`tracing-timing`] implements inter-event timing metrics on top of `tracing`. |
| //! It provides a subscriber that records the time elapsed between pairs of |
| //! `tracing` events and generates histograms. |
| //! - [`tracing-opentelemetry`] provides a subscriber for emitting traces to |
| //! [OpenTelemetry]-compatible distributed tracing systems. |
| //! - [`tracing-honeycomb`] Provides a layer that reports traces spanning multiple machines to [honeycomb.io]. Backed by [`tracing-distributed`]. |
| //! - [`tracing-distributed`] Provides a generic implementation of a layer that reports traces spanning multiple machines to some backend. |
| //! - [`tracing-actix-web`] provides `tracing` integration for the `actix-web` web framework. |
| //! - [`tracing-actix`] provides `tracing` integration for the `actix` actor |
| //! framework. |
| //! - [`tracing-gelf`] implements a subscriber for exporting traces in Greylog |
| //! GELF format. |
| //! - [`tracing-coz`] provides integration with the [coz] causal profiler |
| //! (Linux-only). |
| //! - [`tracing-bunyan-formatter`] provides a layer implementation that reports events and spans |
| //! in [bunyan] format, enriched with timing information. |
| //! - [`tracing-wasm`] provides a `Subscriber`/`Layer` implementation that reports |
| //! events and spans via browser `console.log` and [User Timing API (`window.performance`)]. |
| //! - [`tracing-web`] provides a layer implementation of level-aware logging of events |
| //! to web browsers' `console.*` and span events to the [User Timing API (`window.performance`)]. |
| //! - [`tide-tracing`] provides a [tide] middleware to trace all incoming requests and responses. |
| //! - [`test-log`] takes care of initializing `tracing` for tests, based on |
| //! environment variables with an `env_logger` compatible syntax. |
| //! - [`tracing-unwrap`] provides convenience methods to report failed unwraps |
| //! on `Result` or `Option` types to a `Subscriber`. |
| //! - [`diesel-tracing`] provides integration with [`diesel`] database connections. |
| //! - [`tracing-tracy`] provides a way to collect [Tracy] profiles in instrumented |
| //! applications. |
| //! - [`tracing-elastic-apm`] provides a layer for reporting traces to [Elastic APM]. |
| //! - [`tracing-etw`] provides a layer for emitting Windows [ETW] events. |
| //! - [`tracing-fluent-assertions`] provides a fluent assertions-style testing |
| //! framework for validating the behavior of `tracing` spans. |
| //! - [`sentry-tracing`] provides a layer for reporting events and traces to [Sentry]. |
| //! - [`tracing-forest`] provides a subscriber that preserves contextual coherence by |
| //! grouping together logs from the same spans during writing. |
| //! - [`tracing-loki`] provides a layer for shipping logs to [Grafana Loki]. |
| //! - [`tracing-logfmt`] provides a layer that formats events and spans into the logfmt format. |
| //! - [`reqwest-tracing`] provides a middleware to trace [`reqwest`] HTTP requests. |
| //! |
| //! If you're the maintainer of a `tracing` ecosystem crate not listed above, |
| //! please let us know! We'd love to add your project to the list! |
| //! |
| //! [`tracing-opentelemetry`]: https://crates.io/crates/tracing-opentelemetry |
| //! [OpenTelemetry]: https://opentelemetry.io/ |
| //! [`tracing-honeycomb`]: https://crates.io/crates/tracing-honeycomb |
| //! [`tracing-distributed`]: https://crates.io/crates/tracing-distributed |
| //! [honeycomb.io]: https://www.honeycomb.io/ |
| //! [`tracing-actix-web`]: https://crates.io/crates/tracing-actix-web |
| //! [`tracing-actix`]: https://crates.io/crates/tracing-actix |
| //! [`tracing-gelf`]: https://crates.io/crates/tracing-gelf |
| //! [`tracing-coz`]: https://crates.io/crates/tracing-coz |
| //! [coz]: https://github.com/plasma-umass/coz |
| //! [`tracing-bunyan-formatter`]: https://crates.io/crates/tracing-bunyan-formatter |
| //! [bunyan]: https://github.com/trentm/node-bunyan |
| //! [`tracing-wasm`]: https://docs.rs/tracing-wasm |
| //! [`tracing-web`]: https://docs.rs/tracing-web |
| //! [User Timing API (`window.performance`)]: https://developer.mozilla.org/en-US/docs/Web/API/User_Timing_API |
| //! [`tide-tracing`]: https://crates.io/crates/tide-tracing |
| //! [tide]: https://crates.io/crates/tide |
| //! [`test-log`]: https://crates.io/crates/test-log |
| //! [`tracing-unwrap`]: https://docs.rs/tracing-unwrap |
| //! [`diesel`]: https://crates.io/crates/diesel |
| //! [`diesel-tracing`]: https://crates.io/crates/diesel-tracing |
| //! [`tracing-tracy`]: https://crates.io/crates/tracing-tracy |
| //! [Tracy]: https://github.com/wolfpld/tracy |
| //! [`tracing-elastic-apm`]: https://crates.io/crates/tracing-elastic-apm |
| //! [Elastic APM]: https://www.elastic.co/apm |
| //! [`tracing-etw`]: https://github.com/microsoft/tracing-etw |
| //! [ETW]: https://docs.microsoft.com/en-us/windows/win32/etw/about-event-tracing |
| //! [`tracing-fluent-assertions`]: https://crates.io/crates/tracing-fluent-assertions |
| //! [`sentry-tracing`]: https://crates.io/crates/sentry-tracing |
| //! [Sentry]: https://sentry.io/welcome/ |
| //! [`tracing-forest`]: https://crates.io/crates/tracing-forest |
| //! [`tracing-loki`]: https://crates.io/crates/tracing-loki |
| //! [Grafana Loki]: https://grafana.com/oss/loki/ |
| //! [`tracing-logfmt`]: https://crates.io/crates/tracing-logfmt |
| //! [`reqwest-tracing`]: https://crates.io/crates/reqwest-tracing |
| //! [`reqwest`]: https://crates.io/crates/reqwest |
| //! |
| //! <pre class="ignore" style="white-space:normal;font:inherit;"> |
| //! <strong>Note</strong>: Some of these ecosystem crates are currently |
| //! unreleased and/or in earlier stages of development. They may be less stable |
| //! than <code>tracing</code> and <code>tracing-core</code>. |
| //! </pre> |
| //! |
| //! ## Crate Feature Flags |
| //! |
| //! The following crate [feature flags] are available: |
| //! |
| //! * A set of features controlling the [static verbosity level]. |
| //! * `log`: causes trace instrumentation points to emit [`log`] records as well |
| //! as trace events, if a default `tracing` subscriber has not been set. This |
| //! is intended for use in libraries whose users may be using either `tracing` |
| //! or `log`. |
| //! * `log-always`: Emit `log` records from all `tracing` spans and events, even |
| //! if a `tracing` subscriber has been set. This should be set only by |
| //! applications which intend to collect traces and logs separately; if an |
| //! adapter is used to convert `log` records into `tracing` events, this will |
| //! cause duplicate events to occur. |
| //! * `attributes`: Includes support for the `#[instrument]` attribute. |
| //! This is on by default, but does bring in the `syn` crate as a dependency, |
| //! which may add to the compile time of crates that do not already use it. |
| //! * `std`: Depend on the Rust standard library (enabled by default). |
| //! |
| //! `no_std` users may disable this feature with `default-features = false`: |
| //! |
| //! ```toml |
| //! [dependencies] |
| //! tracing = { version = "0.1.37", default-features = false } |
| //! ``` |
| //! |
| //! <pre class="ignore" style="white-space:normal;font:inherit;"> |
| //! <strong>Note</strong>: <code>tracing</code>'s <code>no_std</code> support |
| //! requires <code>liballoc</code>. |
| //! </pre> |
| //! |
| //! ### Unstable Features |
| //! |
| //! These feature flags enable **unstable** features. The public API may break in 0.1.x |
| //! releases. To enable these features, the `--cfg tracing_unstable` must be passed to |
| //! `rustc` when compiling. |
| //! |
| //! The following unstable feature flags are currently available: |
| //! |
| //! * `valuable`: Enables support for recording [field values] using the |
| //! [`valuable`] crate. |
| //! |
| //! #### Enabling Unstable Features |
| //! |
| //! The easiest way to set the `tracing_unstable` cfg is to use the `RUSTFLAGS` |
| //! env variable when running `cargo` commands: |
| //! |
| //! ```shell |
| //! RUSTFLAGS="--cfg tracing_unstable" cargo build |
| //! ``` |
| //! Alternatively, the following can be added to the `.cargo/config` file in a |
| //! project to automatically enable the cfg flag for that project: |
| //! |
| //! ```toml |
| //! [build] |
| //! rustflags = ["--cfg", "tracing_unstable"] |
| //! ``` |
| //! |
| //! [feature flags]: https://doc.rust-lang.org/cargo/reference/manifest.html#the-features-section |
| //! [field values]: crate::field |
| //! [`valuable`]: https://crates.io/crates/valuable |
| //! |
| //! ## Supported Rust Versions |
| //! |
| //! Tracing is built against the latest stable release. The minimum supported |
| //! version is 1.49. The current Tracing version is not guaranteed to build on |
| //! Rust versions earlier than the minimum supported version. |
| //! |
| //! Tracing follows the same compiler support policies as the rest of the Tokio |
| //! project. The current stable Rust compiler and the three most recent minor |
| //! versions before it will always be supported. For example, if the current |
| //! stable compiler version is 1.45, the minimum supported version will not be |
| //! increased past 1.42, three minor versions prior. Increasing the minimum |
| //! supported compiler version is not considered a semver breaking change as |
| //! long as doing so complies with this policy. |
| //! |
| //! [`log`]: https://docs.rs/log/0.4.6/log/ |
| //! [span]: mod@span |
| //! [spans]: mod@span |
| //! [`Span`]: span::Span |
| //! [`in_scope`]: span::Span::in_scope |
| //! [event]: Event |
| //! [events]: Event |
| //! [`Subscriber`]: subscriber::Subscriber |
| //! [Subscriber::event]: subscriber::Subscriber::event |
| //! [`enter`]: subscriber::Subscriber::enter |
| //! [`exit`]: subscriber::Subscriber::exit |
| //! [`enabled`]: subscriber::Subscriber::enabled |
| //! [metadata]: Metadata |
| //! [`field::display`]: field::display |
| //! [`field::debug`]: field::debug |
| //! [`set_global_default`]: subscriber::set_global_default |
| //! [`with_default`]: subscriber::with_default |
| //! [`tokio-rs/tracing`]: https://github.com/tokio-rs/tracing |
| //! [`tracing-futures`]: https://crates.io/crates/tracing-futures |
| //! [`tracing-subscriber`]: https://crates.io/crates/tracing-subscriber |
| //! [`tracing-log`]: https://crates.io/crates/tracing-log |
| //! [`tracing-timing`]: https://crates.io/crates/tracing-timing |
| //! [`tracing-appender`]: https://crates.io/crates/tracing-appender |
| //! [`env_logger`]: https://crates.io/crates/env_logger |
| //! [`FmtSubscriber`]: https://docs.rs/tracing-subscriber/latest/tracing_subscriber/fmt/struct.Subscriber.html |
| //! [static verbosity level]: level_filters#compile-time-filters |
| //! [instrument]: https://docs.rs/tracing-attributes/latest/tracing_attributes/attr.instrument.html |
| //! [flags]: #crate-feature-flags |
| </span><span class="attribute">#![cfg_attr(not(feature = <span class="string">"std"</span>), no_std)] |
| #![cfg_attr(docsrs, feature(doc_cfg), deny(rustdoc::broken_intra_doc_links))] |
| #![doc(html_root_url = <span class="string">"https://docs.rs/tracing/0.1.37"</span>)] |
| #![doc( |
| html_logo_url = <span class="string">"https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/logo-type.png"</span>, |
| issue_tracker_base_url = <span class="string">"https://github.com/tokio-rs/tracing/issues/" |
| </span>)] |
| #![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 |
| )] |
| |
| #[cfg(not(feature = <span class="string">"std"</span>))] |
| </span><span class="kw">extern crate </span>alloc; |
| |
| <span class="comment">// Somehow this `use` statement is necessary for us to re-export the `core` |
| // macros on Rust 1.26.0. I'm not sure how this makes it work, but it does. |
| </span><span class="attribute">#[allow(unused_imports)] |
| #[doc(hidden)] |
| </span><span class="kw">use </span>tracing_core::<span class="kw-2">*</span>; |
| |
| <span class="attribute">#[doc(inline)] |
| </span><span class="kw">pub use </span><span class="self">self</span>::instrument::Instrument; |
| <span class="kw">pub use </span><span class="self">self</span>::{dispatcher::Dispatch, event::Event, field::Value, subscriber::Subscriber}; |
| |
| <span class="attribute">#[doc(hidden)] |
| </span><span class="kw">pub use </span><span class="self">self</span>::span::Id; |
| |
| <span class="attribute">#[doc(hidden)] |
| </span><span class="kw">pub use </span>tracing_core::{ |
| callsite::{<span class="self">self</span>, Callsite}, |
| metadata, |
| }; |
| <span class="kw">pub use </span>tracing_core::{event, Level, Metadata}; |
| |
| <span class="attribute">#[doc(inline)] |
| </span><span class="kw">pub use </span><span class="self">self</span>::span::Span; |
| <span class="attribute">#[cfg(feature = <span class="string">"attributes"</span>)] |
| #[cfg_attr(docsrs, doc(cfg(feature = <span class="string">"attributes"</span>)))] |
| #[doc(inline)] |
| </span><span class="kw">pub use </span>tracing_attributes::instrument; |
| |
| <span class="attribute">#[macro_use] |
| </span><span class="kw">mod </span>macros; |
| |
| <span class="kw">pub mod </span>dispatcher; |
| <span class="kw">pub mod </span>field; |
| <span class="doccomment">/// Attach a span to a `std::future::Future`. |
| </span><span class="kw">pub mod </span>instrument; |
| <span class="kw">pub mod </span>level_filters; |
| <span class="kw">pub mod </span>span; |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">mod </span>stdlib; |
| <span class="kw">pub mod </span>subscriber; |
| |
| <span class="attribute">#[doc(hidden)] |
| </span><span class="kw">pub mod </span>__macro_support { |
| <span class="kw">pub use </span><span class="kw">crate</span>::callsite::Callsite; |
| <span class="kw">use crate</span>::{subscriber::Interest, Metadata}; |
| <span class="kw">pub use </span>core::concat; |
| |
| <span class="doccomment">/// Callsite implementation used by macro-generated code. |
| /// |
| /// /!\ WARNING: This is *not* a stable API! /!\ |
| /// This type, and all code contained in the `__macro_support` module, is |
| /// a *private* API of `tracing`. It is exposed publicly because it is used |
| /// by the `tracing` macros, but it is not part of the stable versioned API. |
| /// Breaking changes to this module may occur in small-numbered versions |
| /// without warning. |
| </span><span class="kw">pub use </span>tracing_core::callsite::DefaultCallsite <span class="kw">as </span>MacroCallsite; |
| |
| <span class="doccomment">/// /!\ WARNING: This is *not* a stable API! /!\ |
| /// This function, and all code contained in the `__macro_support` module, is |
| /// a *private* API of `tracing`. It is exposed publicly because it is used |
| /// by the `tracing` macros, but it is not part of the stable versioned API. |
| /// Breaking changes to this module may occur in small-numbered versions |
| /// without warning. |
| </span><span class="kw">pub fn </span>__is_enabled(meta: <span class="kw-2">&</span>Metadata<<span class="lifetime">'static</span>>, interest: Interest) -> bool { |
| interest.is_always() || <span class="kw">crate</span>::dispatcher::get_default(|default| default.enabled(meta)) |
| } |
| |
| <span class="doccomment">/// /!\ WARNING: This is *not* a stable API! /!\ |
| /// This function, and all code contained in the `__macro_support` module, is |
| /// a *private* API of `tracing`. It is exposed publicly because it is used |
| /// by the `tracing` macros, but it is not part of the stable versioned API. |
| /// Breaking changes to this module may occur in small-numbered versions |
| /// without warning. |
| </span><span class="attribute">#[inline] |
| #[cfg(feature = <span class="string">"log"</span>)] |
| </span><span class="kw">pub fn </span>__disabled_span(meta: <span class="kw-2">&</span><span class="lifetime">'static </span>Metadata<<span class="lifetime">'static</span>>) -> <span class="kw">crate</span>::Span { |
| <span class="kw">crate</span>::Span::new_disabled(meta) |
| } |
| |
| <span class="doccomment">/// /!\ WARNING: This is *not* a stable API! /!\ |
| /// This function, and all code contained in the `__macro_support` module, is |
| /// a *private* API of `tracing`. It is exposed publicly because it is used |
| /// by the `tracing` macros, but it is not part of the stable versioned API. |
| /// Breaking changes to this module may occur in small-numbered versions |
| /// without warning. |
| </span><span class="attribute">#[inline] |
| #[cfg(not(feature = <span class="string">"log"</span>))] |
| </span><span class="kw">pub fn </span>__disabled_span(<span class="kw">_</span>: <span class="kw-2">&</span><span class="lifetime">'static </span>Metadata<<span class="lifetime">'static</span>>) -> <span class="kw">crate</span>::Span { |
| <span class="kw">crate</span>::Span::none() |
| } |
| |
| <span class="doccomment">/// /!\ WARNING: This is *not* a stable API! /!\ |
| /// This function, and all code contained in the `__macro_support` module, is |
| /// a *private* API of `tracing`. It is exposed publicly because it is used |
| /// by the `tracing` macros, but it is not part of the stable versioned API. |
| /// Breaking changes to this module may occur in small-numbered versions |
| /// without warning. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"log"</span>)] |
| </span><span class="kw">pub fn </span>__tracing_log( |
| meta: <span class="kw-2">&</span>Metadata<<span class="lifetime">'static</span>>, |
| logger: <span class="kw-2">&</span><span class="lifetime">'static </span><span class="kw">dyn </span>log::Log, |
| log_meta: log::Metadata<<span class="lifetime">'_</span>>, |
| values: <span class="kw-2">&</span>tracing_core::field::ValueSet<<span class="lifetime">'_</span>>, |
| ) { |
| logger.log( |
| <span class="kw-2">&</span><span class="kw">crate</span>::log::Record::builder() |
| .file(meta.file()) |
| .module_path(meta.module_path()) |
| .line(meta.line()) |
| .metadata(log_meta) |
| .args(<span class="macro">format_args!</span>( |
| <span class="string">"{}"</span>, |
| <span class="kw">crate</span>::log::LogValueSet { |
| values, |
| is_first: <span class="bool-val">true |
| </span>} |
| )) |
| .build(), |
| ); |
| } |
| } |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"log"</span>)] |
| #[doc(hidden)] |
| </span><span class="kw">pub mod </span>log { |
| <span class="kw">use </span>core::fmt; |
| <span class="kw">pub use </span>log::<span class="kw-2">*</span>; |
| <span class="kw">use </span>tracing_core::field::{Field, ValueSet, Visit}; |
| |
| <span class="doccomment">/// Utility to format [`ValueSet`]s for logging. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>LogValueSet<<span class="lifetime">'a</span>> { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) values: <span class="kw-2">&</span><span class="lifetime">'a </span>ValueSet<<span class="lifetime">'a</span>>, |
| <span class="kw">pub</span>(<span class="kw">crate</span>) is_first: bool, |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'a</span>> fmt::Display <span class="kw">for </span>LogValueSet<<span class="lifetime">'a</span>> { |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| <span class="kw">struct </span>LogVisitor<<span class="lifetime">'a</span>, <span class="lifetime">'b</span>> { |
| f: <span class="kw-2">&</span><span class="lifetime">'a </span><span class="kw-2">mut </span>fmt::Formatter<<span class="lifetime">'b</span>>, |
| is_first: bool, |
| result: fmt::Result, |
| } |
| |
| <span class="kw">impl </span>Visit <span class="kw">for </span>LogVisitor<<span class="lifetime">'_</span>, <span class="lifetime">'_</span>> { |
| <span class="kw">fn </span>record_debug(<span class="kw-2">&mut </span><span class="self">self</span>, field: <span class="kw-2">&</span>Field, value: <span class="kw-2">&</span><span class="kw">dyn </span>fmt::Debug) { |
| <span class="kw">let </span>res = <span class="kw">if </span><span class="self">self</span>.is_first { |
| <span class="self">self</span>.is_first = <span class="bool-val">false</span>; |
| <span class="kw">if </span>field.name() == <span class="string">"message" </span>{ |
| <span class="macro">write!</span>(<span class="self">self</span>.f, <span class="string">"{:?}"</span>, value) |
| } <span class="kw">else </span>{ |
| <span class="macro">write!</span>(<span class="self">self</span>.f, <span class="string">"{}={:?}"</span>, field.name(), value) |
| } |
| } <span class="kw">else </span>{ |
| <span class="macro">write!</span>(<span class="self">self</span>.f, <span class="string">" {}={:?}"</span>, field.name(), value) |
| }; |
| <span class="kw">if let </span><span class="prelude-val">Err</span>(err) = res { |
| <span class="self">self</span>.result = <span class="self">self</span>.result.and(<span class="prelude-val">Err</span>(err)); |
| } |
| } |
| |
| <span class="kw">fn </span>record_str(<span class="kw-2">&mut </span><span class="self">self</span>, field: <span class="kw-2">&</span>Field, value: <span class="kw-2">&</span>str) { |
| <span class="kw">if </span>field.name() == <span class="string">"message" </span>{ |
| <span class="self">self</span>.record_debug(field, <span class="kw-2">&</span><span class="macro">format_args!</span>(<span class="string">"{}"</span>, value)) |
| } <span class="kw">else </span>{ |
| <span class="self">self</span>.record_debug(field, <span class="kw-2">&</span>value) |
| } |
| } |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>visit = LogVisitor { |
| f, |
| is_first: <span class="self">self</span>.is_first, |
| result: <span class="prelude-val">Ok</span>(()), |
| }; |
| <span class="self">self</span>.values.record(<span class="kw-2">&mut </span>visit); |
| visit.result |
| } |
| } |
| } |
| |
| <span class="kw">mod </span>sealed { |
| <span class="kw">pub trait </span>Sealed {} |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="tracing" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |