When instrumenting libraries and applications, the most simple approach requires three steps.
Obtain a tracer¶
auto provider = opentelemetry::trace::Provider::GetTracerProvider(); auto tracer = provider->GetTracer("foo_library", "1.0.0");
TracerProvider acquired in the first step is a singleton object
that is usually provided by the OpenTelemetry C++ SDK. It is used to
provide specific implementations for API interfaces. In case no SDK is
used, the API provides a default no-op implementation of a
Tracer acquired in the second step is needed to create and start
Start a span¶
auto span = tracer->StartSpan("HandleRequest");
This creates a span, sets its name to
"HandleRequest", and sets its
start time to the current time. Refer to the API documentation for other
operations that are available to enrich spans with additional data.
Mark a span as active¶
auto scope = tracer->WithActiveSpan(span);
This marks a span as active and returns a
Scope object bound to the
lifetime of the span. When the
Scope object is destroyed, the
related span is ended.
The concept of an active span is important, as any span that is created without explicitly specifying a parent is parented to the currently active span.