Custom tags for spans of net/httpclient

[tkuenzle]

Is your feature request related to a problem? Please describe.
We are using the skipper/net/httpclient for quite a few services due to it's out-of-the-box support for opentelemetry. Recently a new requirement was raised, that we need to tag all outgoing client spans with specific tags, i.e. peer.service and peer.hostname. Currently, skipper/net/httpclient does only support very few tags, namely kind, component, http.url and http.method of which only component is configurable. We would like to be able to pass any additional tags that we need.

Describe the solution you would like
We would like to have a new option called sth like OpentracingTags or CustomOpentracingTags of type opentracing.Tags. These would be added to each span in addition to the previously supported ones.

Describe alternatives you've considered (optional)
Alternatively we could allow passing some kind of a hook as an option with the span as argument, so that the span could be modified in any way.

Would you like to work on it?
Yes

[szuecs]

@tkuenzle I think it's fine to do the suggested feature with the suggested solution. CustomOpentracingTags sounds good to me.

[AlexanderYastrebov]

I guess CustomOpentracingTags is a static set of tags.
We need to see how hard it is actually to use custom Tracer that overrides StartSpan and injects other tags there. It would allow to add dynamic tags.

[AlexanderYastrebov]

We need to see how hard it is actually to use custom Tracer that overrides StartSpan and injects other tags there.

#2103

[AlexanderYastrebov]

Also we need to keep opentracing/specification#163 in mind before investing more into it, I've created #2104

[tkuenzle]

Thanks for the POC @AlexanderYastrebov. Looks a lot easier than I assumed. It does still feel like a workaround and not like a nice solution though 😄

But especially in the light of opentracing being deprecated I guess it makes sense not to add more opentracing specific options 👍

[AlexanderYastrebov]

@tkuenzle Thank you, then I am closing this.