Trace_simple.Simple_spanA simple span.
This is a concrete representation of spans that is convenient to manipulate.
type t = {name : string;__FUNCTION__ : string option;__FILE__ : string;__LINE__ : int;time_ns : int64;Time the span was entered.
*)mutable time_exit_ns : int64;Time the span was exited. Set at exit, Int64.max_int otherwise
tid : int;Thread in which span was created
*)trace_id : int64;For async spans
*)parent : Trace_core.parent;flavor : span_flavor;params : Trace_core.extension_parameter list;mutable data : (string * Trace_core.user_data) list;Modified by add_data_to_span
}The type of spans used by all subscribers.