Support OpenTelemetry concepts on Activity

[tarekgh]

This issue tracking the work as the part of the issue https://github.com/dotnet/corefx/issues/42305

Please look at dotnet/designs#98 for the detailed design.

[noahfalk]

@tarekgh is the primary dev owner, I am actively assisting. So far design feedback has been occurring in #32660

[reyang]

Looks great! Thanks @tarekgh and @noahfalk!

One question related to

using (Activity foo = new Activity(...))
{
    throw new FoobarException(...);
}

If it is possible to capture the exception and associate it with the Activity?

In OpenTelemetry Python there is such feature (although I think it is more like a question to the language/runtime rather than API) where we know if there is exception and derive status code.

[tarekgh]

Thanks @reyang for your review.

I don't think we can automatically capture the exception inside using block without try-catch. The user can write the code like:

using (Activity foo = Activity.StartNew(...))
{
    try
    {
        throw new FoobarException(...);
    }
    catch (Exception e)
    {
        foo?.SetCustomProperty("Exception", e);
    }
}

and if there is any listener, will get the notification in stopping the activity and then can check if the exception is set there using GetCustomProperty. I'll think if we'll have a better way to handle it.

[reyang]

If developers perform exception handling in a central place (e.g. the evil global exception handler, or catching exception from top level code), is there a way for them to know what's the enclosing activity? (I guess no?)

try {
    using (var foo = new Activity("foo"))
    {
        using (var baz = new Activity("baz")
        {
            DoSomething();
        }
        DoSomething();
    }
    using (var bar = new Activity("bar"))
    {
        DoSomething();
    }
} catch (FoobarException ex) {
    log(
        ex,
        MagicalFunctionWhichReturnsTheEnclosingActivity(ex).Name, // this is hard since activity is disposed already
        MagicalFunctionWhichReturnsTheVeryContext(ex).SpanId,
    );
}