Apache and Jersey Client Inconsistencies

[srapp]

I was messing a bit more with the Apache and Jersey implementations in Brave and noticed a few discrepancies between the two. Most notably, the headers are calculated differently and the attributes associated with the spans were inconsistent as well. It seems like it would be good for the client side tracing to be as consistent as possible between the libraries Brave offers, and I'd like to offer a plan.

We could introduce a shared 'brave-client' module that contains some interceptors which do the appropriate work of computing the header and span info, and also sends the CR and CS events, agnostic to the web client implementation. The implementation of adding a header to a request differs on which client library your using, but we could add RequestAdaptor interface that the shared module delegates to, and then the Jersey and Apache libraries can implement that accordingly.

I admittedly have started down this path in code to see if it could pan out, and I think there's some real promise with it, but I'd like to see what you thought first. I have a branch up in my fork called refactor-clients that has my current progress on the idea and may provide a bit more context about my proposal.

[kristofa]

I agree that it is probably the right time to implement an abstraction on top of the existing ClientTracer and ServerTracer. It should make supporting additional libraries easier, with less code, and more consistent.

I'll do my best to have a closer look in next few days.