Authentication

In general, the google-cloud-storage library uses Service Account credentials to connect to Google Cloud services. When running on Compute Engine the credentials will be discovered automatically. When running on other environments, the Service Account credentials can be specified by providing the path to the JSON keyfile for the account (or the JSON itself) in environment variables. Additionally, Cloud SDK credentials can also be discovered automatically, but this is only recommended during development.

Project and Credential Lookup

The google-cloud-storage library aims to make authentication as simple as possible, and provides several mechanisms to configure your system without providing Project ID and Service Account Credentials directly in code.

Project ID is discovered in the following order:

1. Specify project ID in method arguments
2. Specify project ID in configuration
3. Discover project ID in environment variables
4. Discover GCE project ID

Credentials are discovered in the following order:

1. Specify credentials in method arguments
2. Specify credentials in configuration
3. Discover credentials path in environment variables
4. Discover credentials JSON in environment variables
5. Discover credentials file in the Cloud SDK's path
6. Discover GCE credentials

Google Cloud Platform environments

While running on Google Cloud Platform environments such as Google Compute Engine, Google App Engine and Google Kubernetes Engine, no extra work is needed. The Project ID and Credentials and are discovered automatically. Code should be written as if already authenticated. Just be sure when you set up the GCE instance, you add the correct scopes for the APIs you want to access. For example:

• All APIs
  • https://www.googleapis.com/auth/cloud-platform
  • https://www.googleapis.com/auth/cloud-platform.read-only
• BigQuery
  • https://www.googleapis.com/auth/bigquery
  • https://www.googleapis.com/auth/bigquery.insertdata
• Compute Engine
  • https://www.googleapis.com/auth/compute
• Datastore
  • https://www.googleapis.com/auth/datastore
  • https://www.googleapis.com/auth/userinfo.email
• DNS
  • https://www.googleapis.com/auth/ndev.clouddns.readwrite
• Pub/Sub
  • https://www.googleapis.com/auth/pubsub
• Storage
  • https://www.googleapis.com/auth/devstorage.full_control
  • https://www.googleapis.com/auth/devstorage.read_only
  • https://www.googleapis.com/auth/devstorage.read_write

Environment Variables

The Project ID and Credentials JSON can be placed in environment variables instead of declaring them directly in code. Each service has its own environment variable, allowing for different service accounts to be used for different services. (See the READMEs for the individual service gems for details.) The path to the Credentials JSON file can be stored in the environment variable, or the Credentials JSON itself can be stored for environments such as Docker containers where writing files is difficult or not encouraged.

The environment variables that Storage checks for project ID are:

1. STORAGE_PROJECT
2. GOOGLE_CLOUD_PROJECT

The environment variables that Storage checks for credentials are configured on Google::Cloud::Storage::Credentials:

1. STORAGE_CREDENTIALS - Path to JSON file, or JSON contents
2. STORAGE_KEYFILE - Path to JSON file, or JSON contents
3. GOOGLE_CLOUD_CREDENTIALS - Path to JSON file, or JSON contents
4. GOOGLE_CLOUD_KEYFILE - Path to JSON file, or JSON contents
5. GOOGLE_APPLICATION_CREDENTIALS - Path to JSON file

require "google/cloud/storage"

ENV["STORAGE_PROJECT"]     = "my-project-id"
ENV["STORAGE_CREDENTIALS"] = "path/to/keyfile.json"

storage = Google::Cloud::Storage.new

Configuration

The Project ID and Credentials JSON can be configured instead of placing them in environment variables or providing them as arguments.

require "google/cloud/storage"

Google::Cloud::Storage.configure do |config|
  config.project_id  = "my-project-id"
  config.credentials = "path/to/keyfile.json"
end

storage = Google::Cloud::Storage.new

Cloud SDK

This option allows for an easy way to authenticate during development. If credentials are not provided in code or in environment variables, then Cloud SDK credentials are discovered.

To configure your system for this, simply:

1. Download and install the Cloud SDK
2. Authenticate using OAuth 2.0 $ gcloud auth login
3. Write code as if already authenticated.

NOTE: This is not recommended for running in production. The Cloud SDK should only be used during development.

Creating a Service Account

Google Cloud requires a Project ID and Service Account Credentials to connect to the APIs. You will use the Project ID and JSON key file to connect to most services with google-cloud-storage.

If you are not running this client on Google Compute Engine, you need a Google Developers service account.

1. Visit the Google Developers Console.
2. Create a new project or click on an existing project.
3. Activate the slide-out navigation tray and select API Manager. From here, you will enable the APIs that your application requires.

Note: You may need to enable billing in order to use these services.

1. Select Credentials from the side navigation.

You should see a screen like one of the following.

Find the "Add credentials" drop down and select "Service account" to be guided through downloading a new JSON key file.

If you want to re-use an existing service account, you can easily generate a new key file. Just select the account you wish to re-use, and click "Generate new JSON key":

The key file you download will be used by this library to authenticate API requests and should be stored in a secure location.

Troubleshooting

If you're having trouble authenticating you can ask for help by following the Troubleshooting Guide.