Calling gRPC server via Traffic Director from CloudBuild

[s0s0rhw]

I'm trying to call a GRPC server via traffic director using xds from a CloudBuild step.

I did setup gRPC server running on GKE following instruction in https://cloud.google.com/traffic-director/docs/security-proxyless-setup#bootstrap-security-config-fi.... The instruction runs a test gRPC client on GKE, but I would like to run the test gRPC client from CloudBuild steps.

Calling gRPC server through traffic director requires initializing traffic director bootstrap configuration.
And the configuration includes certificate provider something like this.

...
"certificate_providers": {
  "google_cloud_private_spiffe": {
    "plugin_name": "file_watcher",
    "config": {
      "certificate_file": "/var/run/secrets/workload-spiffe-credentials/certificates.pem",
      "private_key_file": "/var/run/secrets/workload-spiffe-credentials/private_key.pem",
      "ca_certificate_file": "/var/run/secrets/workload-spiffe-credentials/ca_certificates.pem",
      "refresh_interval": "600s"
    }
  }
}
...

Are the 3 files gRPC client certificate files?
How to download the above 3 files from where to the Cloudbuild steps?

Thanks,
Seyoung