Allow setting custom metric attributes in otelhttp transport

[luca-filipponi]

There is no option to include a set of attribute on metrics for every request

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: luca-filipponi / name: Luca Filipponi (710e12a, 90b1f5d, cfcd084, 835a213)
• ✅ login: dmathieu / name: Damien Mathieu (68d3c06, 014e0bf)

[dmathieu]

You shouldn't need this option. The same can be achieved with a view.
https://opentelemetry.io/docs/languages/go/instrumentation/#registering-views

[luca-filipponi]

You shouldn't need this option. The same can be achieved with a view.

Ohh nice, so i guess this is not useful! Will check out how this works

[luca-filipponi]

@dmathieu i've checked out the documentation of the view, but I don't see an option to add attributes with that

you can only filter them?
https://github.com/open-telemetry/opentelemetry-go/blob/82184aa44bb892ad95d98e09196a7c331f17797e/sdk/metric/instrument.go#L146

[dmathieu]

Urgh yes sorry, my bad.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.5%. Comparing base (abb5953) to head (68d3c06).
Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #5876   +/-   ##
=====================================
  Coverage   65.5%   65.5%           
=====================================
  Files        203     203           
  Lines      12926   12936   +10     
=====================================
+ Hits        8474    8486   +12     
+ Misses      4198    4197    -1     
+ Partials     254     253    -1     

Files	Coverage Δ
instrumentation/net/http/otelhttp/config.go	82.0% <100.0%> (+1.1%)	⬆️
instrumentation/net/http/otelhttp/transport.go	95.2% <100.0%> (+0.2%)	⬆️

... and 1 file with indirect coverage changes

[luca-filipponi]

Created an issue: #5877, not sure if this is the best way to add this functionality (maybe there can be an option to add attributes in a the view? but it seems more invasive)

[dmathieu]

Typically, with this kind of attributes in otelhttp and other instrumentations, the follow request we have seen is to be able to set data dynamically, depending on the request data.

I wonder if it would be worth going directly with a callback that accepts the request as a parameter?

[luca-filipponi]

I wonder if it would be worth going directly with a callback that accepts the request as a parameter?

yea, pretty sure I can do that 😄 will send changes in a bit

[luca-filipponi]

@dmathieu what is the process for merging? do you want me to squash commits? is there anything else that i should do?

[dmathieu]

A second approval from a member of @open-telemetry/go-approvers is required before we can merge.

[dashpole]

I think this has been discussed, but I don't remember the outcome. Can you update the description to include it?

Why can't the Labeler be used to accomplish this?

[dmathieu]

It's mentioned in #5877.

[dashpole]

Thanks. Does it need to be a function, then, if the goal is to add constant labels not based on the request? This seems to just duplicate the Labeler's functionality right now.

[dmathieu]

I asked for it to be a function here, as every other option we've set like this before was always followed with a request to be able to dynamically add data rather than statically.
I don't mind reverting that if you feel against it though.

[luca-filipponi]

@hanyuancheung @dmathieu i've squashed all the commits and rebased with main. Let me know if you need me to do something else.