root spans are not recorded with trace_id_ratio_based

[dvic]

I'm not sure what should be done here but this doesn't seem right does it?

trace_id_ratio_based_sampler(_Config) ->
    Tracer = opentelemetry:get_tracer(),

    Sampler1 = otel_sampler:setup(always_on),

    %% this succeeds
    SpanCtx1 = otel_tracer:start_span(Tracer, <<"span-1">>, #{sampler => Sampler1}),
    ?assertMatch(true, SpanCtx1#span_ctx.is_recording),

    Sampler2 = otel_sampler:setup({trace_id_ratio_based, 1.0}),

    %% this fails
    SpanCtx2 = otel_tracer:start_span(Tracer, <<"span-1">>, #{sampler => Sampler2}),
    ?assertMatch(true, SpanCtx2#span_ctx.is_recording),

    ok.

It's because ParentTraceId = trace_id(Ctx), is undefined (in otel_span_utils), and that's because start_span inside opentelemetry/otel_tracer:

start_span(Tracer={Module, _}, Name, Opts) ->
    Module:start_span(otel_ctx:get_current(), Tracer, Name, Opts).

in which otel_ctx:get_current() here returns #{}.

[dvic]

The test case above can be dropped inside opentelemetry_SUITE.erl and run with rebar3 ct --suite apps/opentelemetry/test/opentelemetry_SUITE.erl --case trace_id_ratio_based_sampler

[dvic]

if I move (all in otel_span_utils)

{NewSpanCtx, ParentSpanId} = new_span_ctx(Ctx),

to the top

and use

ParentTraceId = trace_id(NewSpanCtx),

and

trace_id(Ctx) ->
    case Ctx of
        #span_ctx{trace_id = TraceId} ->
            TraceId;
        _ ->
            undefined
    end.

then all tests pass (including the one in this issue).