Module kernel::tracing

Shim to handle tracing v0.1 vs v0.2

NOTE for features used

Unfortunately, we can’t support the case where tracing 0.1 and 0.2 are both selected yet. This might be changed in the future. The following truth table shows the outcome when you select various feature flags.

The _oops_all_tracing_features feature is a “trap” for when the package is built with --all-features, which is usually just for docs and testing. In that case, the feature then ignores the other feature settings, and just picks tracing-01. This is an unfortunate hack that works too well not to use for now.

_oops_all_tracing_features	tracing-01	tracing-02	Outcome
true	don’t care	don’t care	tracing-01 used
false	false	false	Compile Error
false	false	true	tracing-02 used
false	true	false	tracing-01 used
false	true	true	Compile Error

Modules

• callsite
  Callsites represent the source locations from which spans or events originate.
• dispatcher
  Dispatches trace events to Subscribers.
• event
  Events represent single points in time during the execution of a program.
• field
  Span and Event key-value data.
• instrument
  Attach a span to a std::future::Future.
• level_filters
  Trace verbosity level filtering.
• metadata
  Metadata describing trace data.
• span
  Spans represent periods of time in which a program was executing in a particular context.
• subscriber
  Collects and records trace data.

Macros

• debug
  Constructs an event at the debug level.
• debug_span
  Constructs a span at the debug level.
• enabled
  Checks whether a span or event is enabled based on the provided metadata.
• error
  Constructs an event at the error level.
• error_span
  Constructs a span at the error level.
• event
  Constructs a new Event.
• event_enabled
  Tests whether an event with the specified level and target would be enabled.
• info
  Constructs an event at the info level.
• info_span
  Constructs a span at the info level.
• metadata
  Statically constructs new span metadata.
• span
  Constructs a new span.
• span_enabled
  Tests whether a span with the specified level and target would be enabled.
• trace
  Constructs an event at the trace level.
• trace_span
  Constructs a span at the trace level.
• warn
  Constructs an event at the warn level.
• warn_span
  Constructs a span at the warn level.

Structs

• Dispatch
  Dispatch trace data to a Subscriber.
• Event
  Events represent single points in time where something occurred during the execution of a program.
• Id
  Identifies a span within the context of a subscriber.
• Level
  Describes the level of verbosity of a span or event.
• Metadata
  Metadata describing a span or event.
• Span
  A handle representing a span, with the capability to enter the span if it exists.

Traits

• Callsite
  Trait implemented by callsites.
• Instrument
  Attaches spans to a std::future::Future.
• Subscriber
  Trait representing the functions required to collect trace data.
• Value
  A field value of an erased type.

Attribute Macros

• instrument
  Instruments a function to create and enter a tracing span every time the function is called.