Add support for :authority pseudo-header for grpc client

[enuret]

This adds support for configuring authority dial option for grpc exporter

[linux-foundation-easycla]

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• ✅ login: enuret (df80854)

[codeboten]

Thanks for the contribution @enuret. The change looks ok, i'm not familiar w/ the :authority header can you tell me a bit more about the use-case for setting it?

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.04% ⚠️

Comparison is base (81242fa) 90.30% compared to head (df80854) 90.27%.
Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8228      +/-   ##
==========================================
- Coverage   90.30%   90.27%   -0.04%     
==========================================
  Files         301      301              
  Lines       15581    15584       +3     
==========================================
- Hits        14071    14068       -3     
- Misses       1222     1227       +5     
- Partials      288      289       +1     

Files Changed	Coverage Δ
config/configgrpc/configgrpc.go	91.59% <100.00%> (+0.11%)	⬆️

... and 1 file with indirect coverage changes

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[enuret]

Thanks for the contribution @enuret. The change looks ok, i'm not familiar w/ the :authority header can you tell me a bit more about the use-case for setting it?

Hey @codeboten! Thanks for doing the review! This header is a destination host-name by default.

My particular case is configuring envoy to balance traffic between two opentelemetry collectors or between opentelemetry collector and data backend and using envoy virtual hosts to match backends.

So, envoy uses ":authority" header for http/2 requests to match them to virtual hosts: https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_conn_man/route_matching

In my case the example call will look like:
collector (otlpexporter endpoint = envoyhost) -> envoy -> backend

By default, :authority header will be equal "envoyhost" because it is the endpoint address but if "backend" will be specified in :authority header it will be possible to match it based on Virtual host domain name in envoy.

For example, it will let routing based on domain name with configuration like it :

route_config:
  name: local_route
  virtual_hosts:
  - name: backend1
     domains: ["backend1"]
     routes:
     - match:
          prefix: /
        route:
          cluster: backend1

  - name: backend2
     domains: ["backend2"]
     routes:
     - match:
          prefix: /
        route:
          cluster: backend2

[codeboten]

Thanks for the info 👍🏻