Can span be disabled after created?

[MrCroxx]

Hi, I tried to use tracing to do tail-based tracing, which requires to disable a span after it is created or even entered. Is that possible now?

[mladedav]

What does tail-based tracing mean? And what do you mean by disabling a span, filtering it out the next time it should be created?

[MrCroxx]

Hi @mladedav . By tail-based tracing, I mean to cancel a span tree based on the total duration of the root span. I'm not sure if it can be achieved with low overhead with tracing. With minitrace, there is a cancel() method for Span that can do it.

[mladedav]

No, there's no way to filter out a span after it has been created.

If you want to make this decision when the span is closed you need the Layer implementation to do the filtering.

It should be possible to create something like P99Layer<S, T: Layer<S>>(T, PhantomData<S>) where you do some bookkeeping and if the timeout hasn't elapsed you just call the inner Layer.

Note though that this depends on the implementation of the inner layer. E.g. tracing-opentelemetry exports spans in on_close while other layers may export/print partial spans in on_exit which may be called multiple times, specifically both before the timeout and after the timeout for the same span.