[receiver/googlecloudmonitoring, receiver/googlecloudspanner] Add optional config for credentials

[PaulBernier]

Component(s)

receiver/googlecloudmonitoring, receiver/googlecloudspanner

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

I'd like to add the ability to explicitly specify credentials in the receiver config instead of relying on implicit default credentials defined in the environment of the otel collector. We don't always have the possibility to set the credentials in env variables, also we might already have other GCP app running with a different set of credentials. We should offer the flexibility to specify either a path to creds file or the JSON of the creds.

Describe the solution you'd like

I already made this change for receiver/googlecloudpubsub #37255. The maintainer would prefer for that change to be first added to the Google maintained receiver, which is why I open this issue.

Describe alternatives you've considered

No response

Additional context

No response

[github-actions]

Pinging code owners:

• receiver/googlecloudmonitoring: @dashpole @TylerHelmuth @abhishek-at-cloudwerx
• receiver/googlecloudspanner: @dashpole @dsimil @KiranmayiB @harishbohara11

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[github-actions]

Pinging code owners for extension/googleclientauth: @dashpole @aabmass @jsuereth @punya @psx95. See Adding Labels via Comments if you do not have permissions to add labels yourself. For example, comment '/label priority:p2 -needs-triaged' to set the priority and remove the needs-triaged label.

[dashpole]

I would like to try to consolidate these configuration options in the googleclientauth extension's config, if possible, rather than add them to all of the exporters and receivers individually. The exporters and receivers would need to be updated to use the auth extension as a library, and embed the googleclientauth's Config.

[PaulBernier]

@dashpole That would make sense, I was not aware of this extension. But currently I don't see any receiver or exporter in open-telemetry/opentelemetry-collector-contrib having a dependency on googleclientauthextension, is that WIP?

If I follow correctly, it would have to be a contribution to this repo first https://github.com/GoogleCloudPlatform/opentelemetry-operations-go/tree/main/extension/googleclientauthextension and then to https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/googleclientauthextension (that is just a shallow wrapper?), is that correct?

[dashpole]

the googleclientauth extension works (is implemented), but isn't used by the google exporters today. It currently can only be used by components that support pluggable auth.

Yeah... I should move the entire implementation into contrib. But for now, starting with https://github.com/GoogleCloudPlatform/opentelemetry-operations-go/tree/main/extension/googleclientauthextension is the way to go