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//! Metadata describing trace data. use super::{callsite, field}; use crate::stdlib::{fmt, str::FromStr}; /// Metadata describing a [span] or [event]. /// /// All spans and events have the following metadata: /// - A [name], represented as a static string. /// - A [target], a string that categorizes part of the system where the span /// or event occurred. The `tracing` macros default to using the module /// path where the span or event originated as the target, but it may be /// overridden. /// - A [verbosity level]. /// - The names of the [fields] defined by the span or event. /// - Whether the metadata corresponds to a span or event. /// /// In addition, the following optional metadata describing the source code /// location where the span or event originated _may_ be provided: /// - The [file name] /// - The [line number] /// - The [module path] /// /// Metadata is used by [`Subscriber`]s when filtering spans and events, and it /// may also be used as part of their data payload. /// /// When created by the `event!` or `span!` macro, the metadata describing a /// particular event or span is constructed statically and exists as a single /// static instance. Thus, the overhead of creating the metadata is /// _significantly_ lower than that of creating the actual span. Therefore, /// filtering is based on metadata, rather than on the constructed span. /// /// <div class="information"> /// <div class="tooltip ignore" style="">ⓘ<span class="tooltiptext">Note</span></div> /// </div> /// <div class="example-wrap" style="display:inline-block"> /// <pre class="ignore" style="white-space:normal;font:inherit;"> /// <strong>Note</strong>: Although instances of <code>Metadata</code> cannot /// be compared directly, they provide a method <a href="struct.Metadata.html#method.id"> /// <code>id</code></a>, returning an opaque <a href="../callsite/struct.Identifier.html"> /// callsite identifier</a> which uniquely identifies the callsite where the metadata /// originated. This can be used to determine if two <code>Metadata</code> correspond to /// the same callsite. /// </pre></div> /// /// [span]: ../span/index.html /// [event]: ../event/index.html /// [name]: #method.name /// [target]: #method.target /// [fields]: #method.fields /// [verbosity level]: #method.level /// [file name]: #method.file /// [line number]: #method.line /// [module path]: #method.module /// [`Subscriber`]: ../subscriber/trait.Subscriber.html /// [`id`]: struct.Metadata.html#method.id /// [callsite identifier]: ../callsite/struct.Identifier.html pub struct Metadata<'a> { /// The name of the span described by this metadata. name: &'static str, /// The part of the system that the span that this metadata describes /// occurred in. target: &'a str, /// The level of verbosity of the described span. level: Level, /// The name of the Rust module where the span occurred, or `None` if this /// could not be determined. module_path: Option<&'a str>, /// The name of the source code file where the span occurred, or `None` if /// this could not be determined. file: Option<&'a str>, /// The line number in the source code file where the span occurred, or /// `None` if this could not be determined. line: Option<u32>, /// The names of the key-value fields attached to the described span or /// event. fields: field::FieldSet, /// The kind of the callsite. kind: Kind, } /// Indicates whether the callsite is a span or event. #[derive(Clone, Debug, Eq, PartialEq)] pub struct Kind(KindInner); /// Describes the level of verbosity of a span or event. #[derive(Clone, Debug, Eq, PartialEq, Ord, PartialOrd)] pub struct Level(LevelInner); // ===== impl Metadata ===== impl<'a> Metadata<'a> { /// Construct new metadata for a span or event, with a name, target, level, field /// names, and optional source code location. pub const fn new( name: &'static str, target: &'a str, level: Level, file: Option<&'a str>, line: Option<u32>, module_path: Option<&'a str>, fields: field::FieldSet, kind: Kind, ) -> Self { Metadata { name, target, level, module_path, file, line, fields, kind, } } /// Returns the names of the fields on the described span or event. pub fn fields(&self) -> &field::FieldSet { &self.fields } /// Returns the level of verbosity of the described span or event. pub fn level(&self) -> &Level { &self.level } /// Returns the name of the span. pub fn name(&self) -> &'static str { self.name } /// Returns a string describing the part of the system where the span or /// event that this metadata describes occurred. /// /// Typically, this is the module path, but alternate targets may be set /// when spans or events are constructed. pub fn target(&self) -> &'a str { self.target } /// Returns the path to the Rust module where the span occurred, or /// `None` if the module path is unknown. pub fn module_path(&self) -> Option<&'a str> { self.module_path } /// Returns the name of the source code file where the span /// occurred, or `None` if the file is unknown pub fn file(&self) -> Option<&'a str> { self.file } /// Returns the line number in the source code file where the span /// occurred, or `None` if the line number is unknown. pub fn line(&self) -> Option<u32> { self.line } /// Returns an opaque `Identifier` that uniquely identifies the callsite /// this `Metadata` originated from. #[inline] pub fn callsite(&self) -> callsite::Identifier { self.fields.callsite() } /// Returns true if the callsite kind is `Event`. pub fn is_event(&self) -> bool { self.kind.is_event() } /// Return true if the callsite kind is `Span`. pub fn is_span(&self) -> bool { self.kind.is_span() } } impl<'a> fmt::Debug for Metadata<'a> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { let mut meta = f.debug_struct("Metadata"); meta.field("name", &self.name) .field("target", &self.target) .field("level", &self.level); if let Some(path) = self.module_path() { meta.field("module_path", &path); } match (self.file(), self.line()) { (Some(file), Some(line)) => { meta.field("location", &format_args!("{}:{}", file, line)); } (Some(file), None) => { meta.field("file", &format_args!("{}", file)); } // Note: a line num with no file is a kind of weird case that _probably_ never occurs... (None, Some(line)) => { meta.field("line", &line); } (None, None) => {} }; meta.field("fields", &format_args!("{}", self.fields)) .field("callsite", &self.callsite()) .field("kind", &self.kind) .finish() } } #[derive(Clone, Debug, Eq, PartialEq)] enum KindInner { Event, Span, } impl Kind { /// `Event` callsite pub const EVENT: Kind = Kind(KindInner::Event); /// `Span` callsite pub const SPAN: Kind = Kind(KindInner::Span); /// Return true if the callsite kind is `Span` pub fn is_span(&self) -> bool { match self { Kind(KindInner::Span) => true, _ => false, } } /// Return true if the callsite kind is `Event` pub fn is_event(&self) -> bool { match self { Kind(KindInner::Event) => true, _ => false, } } } // ===== impl Level ===== impl Level { /// The "error" level. /// /// Designates very serious errors. pub const ERROR: Level = Level(LevelInner::Error); /// The "warn" level. /// /// Designates hazardous situations. pub const WARN: Level = Level(LevelInner::Warn); /// The "info" level. /// /// Designates useful information. pub const INFO: Level = Level(LevelInner::Info); /// The "debug" level. /// /// Designates lower priority information. pub const DEBUG: Level = Level(LevelInner::Debug); /// The "trace" level. /// /// Designates very low priority, often extremely verbose, information. pub const TRACE: Level = Level(LevelInner::Trace); } impl fmt::Display for Level { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { match *self { Level::TRACE => f.pad("TRACE"), Level::DEBUG => f.pad("DEBUG"), Level::INFO => f.pad("INFO"), Level::WARN => f.pad("WARN"), Level::ERROR => f.pad("ERROR"), } } } #[cfg(feature = "std")] #[cfg_attr(docsrs, doc(cfg(feature = "std")))] impl crate::stdlib::error::Error for ParseLevelError {} impl FromStr for Level { type Err = ParseLevelError; fn from_str(s: &str) -> Result<Self, ParseLevelError> { s.parse::<usize>() .map_err(|_| ParseLevelError { _p: () }) .and_then(|num| match num { 1 => Ok(Level::ERROR), 2 => Ok(Level::WARN), 3 => Ok(Level::INFO), 4 => Ok(Level::DEBUG), 5 => Ok(Level::TRACE), _ => Err(ParseLevelError { _p: () }), }) .or_else(|_| match s { s if s.eq_ignore_ascii_case("error") => Ok(Level::ERROR), s if s.eq_ignore_ascii_case("warn") => Ok(Level::WARN), s if s.eq_ignore_ascii_case("info") => Ok(Level::INFO), s if s.eq_ignore_ascii_case("debug") => Ok(Level::DEBUG), s if s.eq_ignore_ascii_case("trace") => Ok(Level::TRACE), _ => Err(ParseLevelError { _p: () }), }) } } #[repr(usize)] #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, Ord, PartialOrd)] enum LevelInner { /// The "error" level. /// /// Designates very serious errors. Error = 1, /// The "warn" level. /// /// Designates hazardous situations. Warn, /// The "info" level. /// /// Designates useful information. Info, /// The "debug" level. /// /// Designates lower priority information. Debug, /// The "trace" level. /// /// Designates very low priority, often extremely verbose, information. Trace, } /// Returned if parsing a `Level` fails. #[derive(Debug)] pub struct ParseLevelError { _p: (), } impl fmt::Display for ParseLevelError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.pad( "error parsing level: expected one of \"error\", \"warn\", \ \"info\", \"debug\", \"trace\", or a number 1-5", ) } } #[cfg(test)] mod tests { use super::*; #[test] fn level_from_str() { assert_eq!("error".parse::<Level>().unwrap(), Level::ERROR); assert_eq!("4".parse::<Level>().unwrap(), Level::DEBUG); assert!("0".parse::<Level>().is_err()) } }