Use context to stop tracing

[dyladan]

There is a spec issue for this: open-telemetry/opentelemetry-specification#530

Other SIGs such as python, ruby, and Java already have implemented such a system.

I don't believe we need to wait for the spec. Even if the spec never merges, we are still technically allowed to use context to stop tracing as it is an SDK concern.

We are currently using a "magic" http header to signal to the http plugin not to trace, but this doesn't work for DNS.

[michaelgoin]

@dyladan Happy to take a stab at this.

[dyladan]

@michaelgoin great! I assigned you. I was probably going to tackle this by setting the context property in the span processor, but if that doesn't work for you feel free to go your own way

[michaelgoin]

Very sorry for neglecting this for so long. Plan to focus this week and getting something up there.

The one suggested path seems pretty clear around where to check the property and no-op and I'll continue to get more comfortable with how everything is plumbed to make sure that's the right approach.

But I did want to verify what you mean by "setting the context property in the span processor." @dyladan you up for a quick chat either on zoom/whatever or gitter this week? Being new to the project, I just want to make sure I'm really understanding intent.

[dyladan]

Sure, I'm up for a chat. Go ahead and grab a 30m slot on my calendar https://calendly.com/daniel-dyla/30min