[][src]Struct tracing::Metadata

pub struct Metadata<'a> { /* fields omitted */ }

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:

Metadata is used by Subscribers 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.

Note
Note: Although instances of Metadata cannot
be compared directly, they provide a method 
id, returning an opaque 
callsite identifier  which uniquely identifies the callsite where the metadata
originated. This can be used to determine if two Metadata correspond to
the same callsite.

Implementations

impl<'a> Metadata<'a>[src]

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: FieldSet,
    kind: Kind
) -> Metadata<'a>
[src]

Construct new metadata for a span or event, with a name, target, level, field names, and optional source code location.

pub fn fields(&self) -> &FieldSet[src]

Returns the names of the fields on the described span or event.

pub fn level(&self) -> &Level[src]

Returns the level of verbosity of the described span or event.

pub fn name(&self) -> &'static str[src]

Returns the name of the span.

pub fn target(&self) -> &'a str[src]

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 module_path(&self) -> Option<&'a str>[src]

Returns the path to the Rust module where the span occurred, or None if the module path is unknown.

pub fn file(&self) -> Option<&'a str>[src]

Returns the name of the source code file where the span occurred, or None if the file is unknown

pub fn line(&self) -> Option<u32>[src]

Returns the line number in the source code file where the span occurred, or None if the line number is unknown.

pub fn callsite(&self) -> Identifier[src]

Returns an opaque Identifier that uniquely identifies the callsite this Metadata originated from.

pub fn is_event(&self) -> bool[src]

Returns true if the callsite kind is Event.

pub fn is_span(&self) -> bool[src]

Return true if the callsite kind is Span.

Trait Implementations

impl<'a> Debug for Metadata<'a>[src]

Auto Trait Implementations

impl<'a> !RefUnwindSafe for Metadata<'a>

impl<'a> Send for Metadata<'a>

impl<'a> Sync for Metadata<'a>

impl<'a> Unpin for Metadata<'a>

impl<'a> !UnwindSafe for Metadata<'a>

Blanket Implementations

impl<T> Any for T where
    T: 'static + ?Sized
[src]

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

impl<T> From<T> for T[src]

impl<T> Instrument for T[src]

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.