How to create two sibling child span with the same parent span?

[miknyko]

Hi, I am facing a scienario that I need calling func_B and func_C sequentially in funcA.

func A { func_B() func_C() }

In each function, I create a span using tracer.start(ctx, span_name).
I understand each time I called tracer.start(), the ctx will be updated. As a result I will get a span hierarchy like A -> B -> C

However, I would like a structure like
A -> B
-> C

with B and C on the same level(on my backend UI).

I just cannot find a way to do that. Any idea? Many thanks.

[dmathieu]

Hi,

No. Context in go is immutable, it cannot be updated.
When you call tracer.Start, two arguments are returned. The first one is the new context, the second one is the new span.
If your third span is created against the same context as your second one, they will both have the same parent.

For example:

ctx, spanA := tracer.Start(context.Background(), "span A")
newCtx, spanB := tracer.Start(ctx, "span B")
yetAnotherCtx, spanC := tracer.Start(ctx, "span B")

In there, the first created span has no parent, since we create a brand new context for it.
The second one has A as a parent, since we use the context from that span.
The third one also has A as a parent, for the same reason.

[miknyko]

Great answer！Many Thanks.