Feature request: make environment variables compatible with google-cloud-ruby

[timanovsky]

It would be nice if node and ruby applications can use the same configuration environment variables, and same preceding logic. In my particular project I'm using two variables: DATASTORE_EMULATOR_HOST and GCLOUD_KEYFILE_JSON. First have higher priority. If it is unset, datastore client goes to service endpoint specified by content of GCLOUD_KEYFILE_JSON. For node application I need to implement it myself

See how it is used here for example: https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/ea2be47beb32615b2bf69f8a846a684f86c8328c/google-cloud-datastore/lib/google/cloud/datastore/credentials.rb

[stephenplusplus]

We do support the datastore emulator variable, and for JSON, try GOOGLE_APPLICATION_CREDENTIALS, which comes from when you authenticate using the gcloud SDK, but you can set the env var manually to point to a JSON key file. That should be supported in Ruby as well.

[stephenplusplus]

Going to close @timanovsky, but let me know if GOOGLE_APPLICATION_CREDENTIALS doesn't do the trick.

[lukewlms]

There's a solution here for using environment variables instead of an on-disk file (critical for our Heroku setup).

You can authenticate with credentials: { private_key, client_email } rather than path to a json file.