dvSpanZoneKey top-level constant

Object const dvSpanZoneKey

The zone key the current span hangs on.

A zone rather than a parameter threaded through every function: a query three calls deep has to be able to hang a child span off the request's without each function in between taking a span it does not otherwise use. That threading is exactly the boilerplate that stops people instrumenting anything.

It lives here rather than beside the HTTP middleware that first set it, because logging needs to read it too and a log line that cannot name the trace it happened inside is half of an investigation.

Implementation

const Object dvSpanZoneKey = #dartvelSpan;