Support service tags

[mustafaakin]

Requirement - what kind of business use case are you trying to solve?

OpenTracing specification added service tags:

opentracing/specification@f7ca62c

Problem - what in Jaeger blocks you from solving the requirement?

It is not implemented yet.

Proposal - what do you suggest to solve the problem or improve the existing situation?

We should implement it. Seems like a good first contribution.

Any open questions to address

Nothing now. Just override the service name in tracer, if a service tag exists?

[jpkrohling]

Would you like to contribute a patch?

[mustafaakin]

Would love to, any pointers on how to approach it?

[jpkrohling]

If I'm reading the spec correctly, it might be sufficient to just change the JaegerSpan#getServiceName to return the contents of a tag named service if there's one, or keep its current behavior in case there's none.

But join our bi-weekly call today, it's a good topic to discuss as it might affect other clients (Go, Python, ...).

[yurishkuro]

I think this change is best done on the server side

[jpkrohling]

@mustafaakin we just talked about it during today's bi-weekly meeting. There were a few ideas around and the best one seems to be by implementing a span filter/adjuster on the backend side.

Are you comfortable coding in Go? If so, you can take a look at the current adjusters there under https://github.com/jaegertracing/jaeger/tree/master/model/adjuster

[mustafaakin]

Sorry could not attend the meeting, implementing it in the serve is more reasonable. I can contribute in Go, no problem. I will have a look and send a pr

[yurishkuro]

Replacing with the ticket for the backend jaegertracing/jaeger#936.