6cb5718eaa
* Update module versions * Prepare stable-v1 for version v1.12.0 * Prepare experimental-metrics for version v0.35.0 * Prepare experimental-schema for version v0.0.4 * Update the CHANGELOG * Undo bump to experimental-schema Revert to original version as nothing has changed. * Fix PR number in changelog * Move change from #3497 into current release
"Passthrough" setup for OpenTelemetry
Some Go programs may wish to propagate context without recording spans. To do this in OpenTelemetry, simply install TextMapPropagators, but do not install a TracerProvider using the SDK. This works because the default TracerProvider implementation returns a "Non-Recording" span that keeps the context of the caller but does not record spans.
For example, when you initialize your global settings, the following will propagate context without recording spans:
// Setup Propagators only
otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(propagation.TraceContext{}, propagation.Baggage{}))
But the following will propagate context and create new, potentially recorded spans:
// Setup SDK
exp, _ := stdout.New(stdout.WithPrettyPrint())
tp = sdktrace.NewTracerProvider(
sdktrace.WithBatcher(exp),
)
otel.SetTracerProvider(tp)
// Setup Propagators
otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(propagation.TraceContext{}, propagation.Baggage{}))
The Demo
The demo has the following call structure:
Outer -> Passthrough -> Inner
If all components had both an SDK and propagators registered, we would expect the trace to look like:
|-------outer---------|
|-Passthrough recv-|
|Passthrough send|
|---inner---|
However, in this demo, only the outer and inner have TracerProvider backed by the SDK. All components have Propagators set. In this case, we expect to see:
|-------outer---------|
|---inner---|