diff options
Diffstat (limited to 'src/lib.rs')
| -rw-r--r-- | src/lib.rs | 234 |
1 files changed, 217 insertions, 17 deletions
@@ -6,7 +6,7 @@ //! //! Note that this macro is also re-exported by the main `tracing` crate. //! -//! *Compiler support: [requires `rustc` 1.49+][msrv]* +//! *Compiler support: [requires `rustc` 1.56+][msrv]* //! //! [msrv]: #supported-rust-versions //! @@ -16,7 +16,7 @@ //! //! ```toml //! [dependencies] -//! tracing = "0.1" +//! tracing-attributes = "0.1.24" //! ``` //! //! The [`#[instrument]`][instrument] attribute can now be added to a function @@ -35,28 +35,28 @@ //! ``` //! //! [`tracing`]: https://crates.io/crates/tracing -//! [instrument]: macro@instrument //! [span]: https://docs.rs/tracing/latest/tracing/span/index.html +//! [instrument]: macro@self::instrument //! //! ## 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 +//! version is 1.56. 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 +//! stable compiler version is 1.69, the minimum supported version will not be +//! increased past 1.66, 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. //! #![doc( html_logo_url = "https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/logo-type.png", - html_favicon_url = "https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/favicon.ico", issue_tracker_base_url = "https://github.com/tokio-rs/tracing/issues/" )] +#![cfg_attr(docsrs, deny(rustdoc::broken_intra_doc_links))] #![warn( missing_debug_implementations, missing_docs, @@ -77,6 +77,9 @@ unused_parens, while_true )] +// TODO: once `tracing` bumps its MSRV to 1.42, remove this allow. +#![allow(unused)] +extern crate proc_macro; use proc_macro2::TokenStream; use quote::{quote, ToTokens}; @@ -88,7 +91,7 @@ mod expand; /// Instruments a function to create and enter a `tracing` [span] every time /// the function is called. /// -/// Unless overriden, a span with `info` level will be generated. +/// Unless overridden, a span with the [`INFO`] [level] will be generated. /// The generated span's name will be the name of the function. /// By default, all arguments to the function are included as fields on the /// span. Arguments that are `tracing` [primitive types] implementing the @@ -96,27 +99,217 @@ mod expand; /// not implement `Value` will be recorded using [`std::fmt::Debug`]. /// /// [primitive types]: https://docs.rs/tracing/latest/tracing/field/trait.Value.html#foreign-impls -/// [`Value` trait]: https://docs.rs/tracing/latest/tracing/field/trait.Value.html +/// [`Value` trait]: https://docs.rs/tracing/latest/tracing/field/trait.Value.html. +/// +/// # Overriding Span Attributes +/// +/// To change the [name] of the generated span, add a `name` argument to the +/// `#[instrument]` macro, followed by an equals sign and a string literal. For +/// example: +/// +/// ``` +/// # use tracing_attributes::instrument; +/// +/// // The generated span's name will be "my_span" rather than "my_function". +/// #[instrument(name = "my_span")] +/// pub fn my_function() { +/// // ... do something incredibly interesting and important ... +/// } +/// ``` +/// +/// To override the [target] of the generated span, add a `target` argument to +/// the `#[instrument]` macro, followed by an equals sign and a string literal +/// for the new target. The [module path] is still recorded separately. For +/// example: +/// +/// ``` +/// pub mod my_module { +/// # use tracing_attributes::instrument; +/// // The generated span's target will be "my_crate::some_special_target", +/// // rather than "my_crate::my_module". +/// #[instrument(target = "my_crate::some_special_target")] +/// pub fn my_function() { +/// // ... all kinds of neat code in here ... +/// } +/// } +/// ``` +/// +/// Finally, to override the [level] of the generated span, add a `level` +/// argument, followed by an equals sign and a string literal with the name of +/// the desired level. Level names are not case sensitive. For example: +/// +/// ``` +/// # use tracing_attributes::instrument; +/// // The span's level will be TRACE rather than INFO. +/// #[instrument(level = "trace")] +/// pub fn my_function() { +/// // ... I have written a truly marvelous implementation of this function, +/// // which this example is too narrow to contain ... +/// } +/// ``` +/// +/// # Skipping Fields +/// +/// To skip recording one or more arguments to a function or method, pass +/// the argument's name inside the `skip()` argument on the `#[instrument]` +/// macro. This can be used when an argument to an instrumented function does +/// not implement [`fmt::Debug`], or to exclude an argument with a verbose or +/// costly `Debug` implementation. Note that: /// -/// To skip recording a function's or method's argument, pass the argument's name -/// to the `skip` argument on the `#[instrument]` macro. For example, -/// `skip` can be used when an argument to an instrumented function does -/// not implement [`fmt::Debug`], or to exclude an argument with a verbose -/// or costly Debug implementation. Note that: /// - multiple argument names can be passed to `skip`. /// - arguments passed to `skip` do _not_ need to implement `fmt::Debug`. /// +/// You can also use `skip_all` to skip all arguments. +/// +/// ## Examples +/// +/// ``` +/// # use tracing_attributes::instrument; +/// # use std::collections::HashMap; +/// // This type doesn't implement `fmt::Debug`! +/// struct NonDebug; +/// +/// // `arg` will be recorded, while `non_debug` will not. +/// #[instrument(skip(non_debug))] +/// fn my_function(arg: usize, non_debug: NonDebug) { +/// // ... +/// } +/// +/// // These arguments are huge +/// #[instrument(skip_all)] +/// fn my_big_data_function(large: Vec<u8>, also_large: HashMap<String, String>) { +/// // ... +/// } +/// ``` +/// +/// Skipping the `self` parameter: +/// +/// ``` +/// # use tracing_attributes::instrument; +/// #[derive(Debug)] +/// struct MyType { +/// data: Vec<u8>, // Suppose this buffer is often quite long... +/// } +/// +/// impl MyType { +/// // Suppose we don't want to print an entire kilobyte of `data` +/// // every time this is called... +/// #[instrument(skip(self))] +/// pub fn my_method(&mut self, an_interesting_argument: usize) { +/// // ... do something (hopefully, using all that `data`!) +/// } +/// } +/// ``` +/// +/// # Adding Fields +/// /// Additional fields (key-value pairs with arbitrary data) can be passed to /// to the generated span through the `fields` argument on the /// `#[instrument]` macro. Strings, integers or boolean literals are accepted values /// for each field. The name of the field must be a single valid Rust -/// identifier, nested (dotted) field names are not supported. +/// identifier, nested (dotted) field names are not supported. Any +/// Rust expression can be used as a field value in this manner. These +/// expressions will be evaluated at the beginning of the function's body, so +/// arguments to the function may be used in these expressions. Field names may +/// also be specified *without* values. Doing so will result in an [empty field] +/// whose value may be recorded later within the function body. /// /// Note that overlap between the names of fields and (non-skipped) arguments /// will result in a compile error. /// +/// ## Examples +/// +/// Adding a new field based on the value of an argument: +/// +/// ``` +/// # use tracing_attributes::instrument; +/// +/// // This will record a field named "i" with the value of `i` *and* a field +/// // named "next" with the value of `i` + 1. +/// #[instrument(fields(next = i + 1))] +/// pub fn my_function(i: usize) { +/// // ... +/// } +/// ``` +/// +/// Recording specific properties of a struct as their own fields: +/// +/// ``` +/// # mod http { +/// # pub struct Error; +/// # pub struct Response<B> { pub(super) _b: std::marker::PhantomData<B> } +/// # pub struct Request<B> { _b: B } +/// # impl<B> std::fmt::Debug for Request<B> { +/// # fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { +/// # f.pad("request") +/// # } +/// # } +/// # impl<B> Request<B> { +/// # pub fn uri(&self) -> &str { "fake" } +/// # pub fn method(&self) -> &str { "GET" } +/// # } +/// # } +/// # use tracing_attributes::instrument; +/// +/// // This will record the request's URI and HTTP method as their own separate +/// // fields. +/// #[instrument(fields(http.uri = req.uri(), http.method = req.method()))] +/// pub fn handle_request<B>(req: http::Request<B>) -> http::Response<B> { +/// // ... handle the request ... +/// # http::Response { _b: std::marker::PhantomData } +/// } +/// ``` +/// +/// This can be used in conjunction with `skip` or `skip_all` to record only +/// some fields of a struct: +/// ``` +/// # use tracing_attributes::instrument; +/// // Remember the struct with the very large `data` field from the earlier +/// // example? Now it also has a `name`, which we might want to include in +/// // our span. +/// #[derive(Debug)] +/// struct MyType { +/// name: &'static str, +/// data: Vec<u8>, +/// } +/// +/// impl MyType { +/// // This will skip the `data` field, but will include `self.name`, +/// // formatted using `fmt::Display`. +/// #[instrument(skip(self), fields(self.name = %self.name))] +/// pub fn my_method(&mut self, an_interesting_argument: usize) { +/// // ... do something (hopefully, using all that `data`!) +/// } +/// } +/// ``` +/// +/// Adding an empty field to be recorded later: +/// +/// ``` +/// # use tracing_attributes::instrument; +/// +/// // This function does a very interesting and important mathematical calculation. +/// // Suppose we want to record both the inputs to the calculation *and* its result... +/// #[instrument(fields(result))] +/// pub fn do_calculation(input_1: usize, input_2: usize) -> usize { +/// // Rerform the calculation. +/// let result = input_1 + input_2; +/// +/// // Record the result as part of the current span. +/// tracing::Span::current().record("result", &result); +/// +/// // Now, the result will also be included on this event! +/// tracing::info!("calculation complete!"); +/// +/// // ... etc ... +/// # 0 +/// } +/// ``` +/// /// # Examples +/// /// Instrumenting a function: +/// /// ``` /// # use tracing_attributes::instrument; /// #[instrument] @@ -229,8 +422,8 @@ mod expand; /// 42 /// } /// ``` -/// The level of the return value event defaults to the same level as the span generated by `#[instrument]`. -/// By default, this will be `TRACE`, but if the span level is overridden, the event will be at the same +/// The return value event will have the same level as the span generated by `#[instrument]`. +/// By default, this will be [`INFO`], but if the level is overridden, the event will be at the same /// level. /// /// It's also possible to override the level for the `ret` event independently: @@ -353,6 +546,13 @@ mod expand; /// ``` /// /// [span]: https://docs.rs/tracing/latest/tracing/span/index.html +/// [name]: https://docs.rs/tracing/latest/tracing/struct.Metadata.html#method.name +/// [target]: https://docs.rs/tracing/latest/tracing/struct.Metadata.html#method.target +/// [level]: https://docs.rs/tracing/latest/tracing/struct.Level.html +/// [module path]: https://docs.rs/tracing/latest/tracing/struct.Metadata.html#method.module_path +/// [`INFO`]: https://docs.rs/tracing/latest/tracing/struct.Level.html#associatedconstant.INFO +/// [empty field]: https://docs.rs/tracing/latest/tracing/field/struct.Empty.html +/// [field syntax]: https://docs.rs/tracing/latest/tracing/#recording-fields /// [`follows_from`]: https://docs.rs/tracing/latest/tracing/struct.Span.html#method.follows_from /// [`tracing`]: https://github.com/tokio-rs/tracing /// [`fmt::Debug`]: std::fmt::Debug |