Tonic Interceptor

[blogle]

Adds optional config for an interceptor to enable modifying each outbound metrics request.

For example - my company has a centralized opentelemetry-collector that gives our SRE team flexibility to determine where they should pipe and store metrics that feed into grafana. This central collector sits behind google IAP. Each internal service needs to supply an oauth token in the grpc headers to publish metrics to this endpoint. This PR exposes the machinery for applications to access the request object and supply such metadata.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: blogle / name: Brandon Ogle (18223c6, 307478f, a915cd4)

[jtescher]

Thanks for getting this started, makes sense to have interceptor support, added some comments.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (57147b1) 69.9% compared to head (32f6af3) 69.9%.

Additional details and impacted files

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  Coverage   69.9%   69.9%           
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  Files        116     116           
  Lines       9027    9027           
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  Hits        6316    6316           
  Misses      2711    2711           

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[blogle]

bump @jtescher

Is anything else you would like to see on this PR? Getting this auth setup working is becoming a higher priority for our team, so would be great to get this integrated.

[TommyCpp]

Sorry didn't get a chance to take a look over the weekend. I will take a look before cut 0.19 release

[blogle]

Is this the only item going into the 0.19 release? If so what needs to be done to move this forward? We would really like to start migrating our metrics, but this has been a blocking issue for us.

[cijothomas]

@blogle Not a comment on the PR content, but a general rule - the CLA check must be cleared before any PRs can be accepted. Could you sign the CLA check? (you may need to consult your employer to see if there are any legal steps to be followed)

[hdost]

Looks like you've addressed @jtescher suggestions but yes you'll need to need to sign the CLA.
Thank you for your contribution!

[TommyCpp]

Probably need to address the lint issue also. But I can take a look if needed

[blogle]

CLA should now be cleared up. @TommyCpp as for the lints, I believe those pub warnings are pre-existing as I don't think I touched visibility of anything. That said, if this is blocking the PR, I can probably make those all pub(crate) since TonicExporterBuilder is the actual public interface there.

[TommyCpp]

Looks like it needs your approval cc @jtescher

[TommyCpp]

I have pushed a change to fix the lint issue and make the configurations public