Macro duration

macro_rules! duration {
    ($category:expr, $name:expr $(, $key:expr => $val:expr)* $(,)?) => { ... };
}

Convenience macro for the duration function that can be used to trace the duration of a scope. If you need finer grained control over when a duration starts and stops, see duration_begin and duration_end.

Example:

  {
      duration!(c"foo", c"bar", "x" => 5, "y" => 10);
      ...
      ...
      // event will be recorded on drop.
  }

is equivalent to

  {
      let mut args;
      let _scope =  {
          static CACHE: trace_site_t = trace_site_t::new(0);
          if let Some(_context) = TraceCategoryContext::acquire_cached(c"foo", &CACHE) {
              args = [ArgValue::of("x", 5), ArgValue::of("y", 10)];
              Some($crate::duration(c"foo", c"bar", &args))
          } else {
              None
          }
      };
      ...
      ...
      // event will be recorded on drop.
  }