How to nest multiple Span?

[holicc]

this code can not nest Span instead Create a new span without relation

let parent_cx =
        opentelemetry::global::get_text_map_propagator(|propagator| propagator.extract(&header));
let span = tracing::info_span!(target: "otel::tracing", "Request");

span.set_parent(parent_cx.clone());
let _enter = span.enter();

    {
        let test_span = tracing::info_span!("TEST");
        test_span.set_parent(parent_cx);
        let _enter = test_span.enter();
        tracing::info!("test span");
    }

[ymgyt]

How about the following code?

 {
        let test_span = tracing::info_span!("TEST");
        // test_span.set_parent(parent_cx);
        let _enter = test_span.enter();
        tracing::info!("test span");
 }

[holicc]

Yes,it works. But why? I need to set the parent context.

[ymgyt]

The parent-child relationship of spans is managed by the tracing-subscriber's Registry, so even without specifying a parent, the span on the stack is maintained as the parent span.
The information is maintained in the hierarchy parent_cx <- span <- test_span. Wouldn't this meet the requirements?

[holicc]

The parent-child relationship of spans is managed by the tracing-subscriber's Registry, so even without specifying a parent, the span on the stack is maintained as the parent span. The information is maintained in the hierarchy parent_cx <- span <- test_span. Wouldn't this meet the requirements?

Yes, but I got two distinct spans.

• span
• test_span

You mean I shouldn't set_parent and instead let the Register manage itself?

[holicc]

Oh, I know why the spans are not nested. It's because I created a span first and did not set its parent, so I got root_span <- span (with new context) <- test_span. I broke the hierarchy of Register. So I created a root_span with context to fix the problem.