link.exs

  test "create Span with Link to outer Span in Task" do
    :otel_batch_processor.set_exporter(:otel_exporter_pid, self())
    OpenTelemetry.register_tracer(:test_tracer, "0.1.0")

    parent_ctx = Ctx.new()

    # create the parent span
    parent = Tracer.start_span("parent")
    # make a new context with it as the active span
    ctx = Tracer.set_current_span(parent_ctx, parent)
    # attach this context (put it in the process dictionary)
    Ctx.attach(ctx)

    task = Task.async(
      fn ->
        # new process has a new context so this span will have no parent
        parent_link = OpenTelemetry.link(parent)
        assert parent_link != :undefined
        Tracer.with_span "child", %{links: [parent_link]} do
          :hello
        end
      end)

    ret = Task.await(task)
    assert :hello = ret

    assert_receive {:span,
                    span(
                      name: "child",
                      parent_span_id: :undefined,
                      links: [_]
                    )}
  end

test.exs

  test "create child Span in Task" do
    :otel_batch_processor.set_exporter(:otel_exporter_pid, self())
    OpenTelemetry.register_tracer(:test_tracer, "0.1.0")

    # create the parent span
    parent = Tracer.start_span("parent")
    # make a new context with it as the active span
    ctx = Tracer.set_current_span(Ctx.new(), parent)
    # attach this context (put it in the process dictionary)
    Ctx.attach(ctx)

    # start the child and set it to current in an unattached context
    child = Tracer.start_span("child")
    ctx = Tracer.set_current_span(ctx, SpanCtx)

    task = Task.async(
      fn ->
        # attach the context with the child span active to this process
        Ctx.attach(ctx)
        Span.end_span(child)
        :hello
      end)

    ret = Task.await(task)
    assert :hello = ret

    span_ctx(span_id: parent_span_id) = Span.end_span(parent)

    assert_receive {:span,
                    span(
                      name: "child",
                      parent_span_id: ^parent_span_id
                    )}
  end