The five span.kind values, by name.

span.kind tells Datadog what part a span played in a call: whether the service received the work or sent it, produced a message or consumed one. The backend reads it to build the service map and to infer the services a trace touched but never entered — a database, a queue, an API nobody instrumented.

Integrations set it; so does hand-written instrumentation around a client call the library does not know about:

DDTrace.trace "stripe.charge", type: "http" do
  DDTrace.set_tag("span.kind", DDTrace.Kind.client())
  charge(order)
end

internal is the one you do not set

A span with no kind is internal already: it is the value the backend assumes, so writing it says nothing a reader could not infer. It has a name here because the closed set is worth spelling whole — reading a kind back off a span, or matching on one, needs the name that means "no kind at all".

The functions exist to spell the values without a typo; the raw strings are equally valid everywhere.

Examples

iex> DDTrace.Kind.server()
"server"