provides support for TracingMetadata

[OlegDokuka]

closes #583

Signed-off-by: Oleh Dokuka shadowgun@i.ua

[OlegDokuka]

cc\ @adriancole your feedback is really appreciated (also see https://github.com/rsocket/rsocket/blob/master/Extensions/Tracing-Zipkin.md for more info)

[codefromthecrypt]

I'd suggest focusing on the outputs vs the inputs. Ex instead of describing features like isSamplingEnabled and isDebuggingEnabled (knowing there may be different sampling algos etc).. focus only on the resulting data that you'd take action on.

isReported -> isSampled: https://github.com/openzipkin/brave/blob/master/brave/src/main/java/brave/propagation/SamplingFlags.java#L83

if you want to support debug you should also know the difference between this and sampled
isDebug: https://github.com/openzipkin/brave/blob/master/brave/src/main/java/brave/propagation/SamplingFlags.java#L108

Not now, but just fyi, there's a third option which is that data is sampled, but it is not propagated in primary trace headers/frames. This is for recording everything for local processing such as metrics or secondary sampling

isSampledLocal:
https://github.com/openzipkin/brave/blob/master/brave/src/main/java/brave/propagation/SamplingFlags.java#L100

Hope this helps!

[spencergibb]

He's trying to implement the extension spec he mentioned.

[codefromthecrypt]

sorry missed that link.. I saw "Add Zipkin Tracing Flyweight" and had no idea what it meant.

In that case, just retain comments about isSampled and isDebug and forget about isSampledLocal as that's not propagated.

[OlegDokuka]

Alright, by looking more into all the stuff I tend to say that current RSocket spec is incorrect and misaligned with today's implementation of TraceContext that I found at brave. Fixing that first and then continue on this impl

[OlegDokuka]

@adriancole do you have a few minutes to chat on the TraceContext topic and discuss all the flags that it has and their importance / behavior?

[codefromthecrypt]

ok find me here https://gitter.im/openzipkin/zipkin