Expose custom round tripper in confighttp.ClientSettings as an extension

[pavankrish123]

Is your feature request related to a problem? Please describe.

We already have defined custom round tripper as a part of HTTPClientSettings in confighttp.go. This has been done to provide some help with testing. However, It is not exposed as a configuration/plugin.

We are running into variety of use cases where we are ending up with requirement to "plug in" a custom round tripper/interceptor of export requests/responses around 1) auditing 2) logging 3) capturing some business specific metrics.

If the custom round tripper is exposed as an extension (akin to how we are doing auth class extensions) - Users can plugin their own custom interceptors extensions on http exporters without need to modifying new exporters/modifying core similar to how we plug in auth.

Describe the solution you'd like
something like

extensions:
  mycustomroundtripper:

exporters:
  otlphttp/withroundtripper:
    endpoint: http://localhost:9000
    inteceptors:
      roundtrippers:  [mycustomroundtripper, ....]

cc: @pureklkl @svrnm

[Sprakhar97]

Hey @pavankrish123, if this feature request is still valid I would like to work on it.

[pavankrish123]

Thanks @Sprakhar97 - Can you please check with @jpkrohling before starting on this feature.

[jpkrohling]

Related to open-telemetry/opentelemetry-collector-contrib#6908

[jpkrohling]

@open-telemetry/collector-approvers, what's your opinion on this? I think it's a good idea to have this, as it would also help with the "authorization" use case.

I would design it a bit differently, though: I would attempt to make this generic so that this can be applied to both gRPC and HTTP transports. And use the word "interceptor" instead of "roundtripper".

[tigrannajaryan]

@jpkrohling The idea sounds interesting but I am not sure we want to work on it right now. Given that we want to stabilize our API asap I think we want to direct our efforts towards that.

[jpkrohling]

Agree, I'll label it accordingly

[milas]

Is this something a PR would be welcome for at this time? I can possibly contribute this.

[disclaimer: employee of Docker Inc]

[jpkrohling]

Yes, we wanted to prepare support for generic interceptors first though:

#7441
open-telemetry/opentelemetry-collector-contrib#6908

Would you like to help with that as well?

[atoulme]

I am going to close this issue as not planned at this time. Please reopen if this is till being worked on.