ruby AWS sdk, auth, and greengrass issues.

I'm trying to follow the docs about using greengrass component based auth, and run into a confusing situation.

Ive read that in a greengrass environment, as long as the automatic environment variables are set, auth is handled automatically.

(specifically, AWS_CONTAINER_AUTHORIZATION_TOKEN and AWS_CONTAINER_CREDENTIALS_FULL_URI)

This actually works great when I use a dummy test ruby program, to do things like

wrapper = Aws::IAM::Client.new wrapper.get_user

But when I swap out my test program, for fluentd, using the timestream plugin at https://github.com/StudistCorporation/fluent-plugin-timestream

it bombs out with an auth error,

failed to flush the buffer. retry_times=0 next_retry_time=2023-04-12 17:54:12 +0000 chunk="5f9274b9cd65f79f9897b62d5fca25ed" error_class=Aws::Errors::EndpointDiscoveryError error="Endpoint discovery failed for the operation or discovered endpoint is not working, request will keep failing until endpoint discovery succeeds or :endpoint option is provided."

This is making no sense to me. How can the same(?) ruby aws lib work in one case, but fail in the other?

For what it's worth, this is using ubuntu 20.04