pub struct Metadata<'a> { }
Expand description
Metadata describing a span or event.
All spans and events have the following metadata:
tracing
macros default to using the module path where the span or event originated as the target, but it may be overridden.Level
type for details.In addition, the following optional metadata describing the source code location where the span or event originated may be provided:
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.
In well-behaved applications, two Metadata
with equal callsite identifiers will be equal in all other ways (i.e., have the same name
, target
, etc.). Consequently, in release builds, Metadata::eq
only checks that its arguments have equal callsites. However, the equality of Metadata
’s other fields is checked in debug builds.
Construct new metadata for a span or event, with a name, target, level, field names, and optional source code location.
SourceReturns the names of the fields on the described span or event.
SourceReturns the level of verbosity of the described span or event.
SourceReturns the name of the span.
SourceReturns 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.
SourceReturns the path to the Rust module where the span occurred, or None
if the module path is unknown.
Returns the name of the source code file where the span occurred, or None
if the file is unknown
Returns the line number in the source code file where the span occurred, or None
if the line number is unknown.
Returns an opaque Identifier
that uniquely identifies the callsite this Metadata
originated from.
Returns true if the callsite kind is Event
.
Return true if the callsite kind is Span
.
Tests for self
and other
values to be equal, and is used by ==
.
Tests for !=
. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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