Add traces/zipkin support to simplify troubleshooting of slow requests

[dlg99]

FEATURE REQUEST

1. Please describe the feature you are requesting.

Add traces/zipkin support to simplify troubleshooting of slow requests

2. Indicate the importance of this issue to you (blocker, must-have, should-have, nice-to-have). Are you currently using any workarounds to address this issue?

Should have.

3. Provide any additional detail on your proposed use case for this feature.

Tracing compliments metrics framework by enabling one's deep dive into performance details of single request. Zipkin provides UI to view such traces though there are other implementations.
Opentracing provides framework for tracing that can be used with various tracing backends, zipkin included.

[sijie]

@dlg99 are you still actively working on it?