In general, the google-cloud-datastore library uses Service Account credentials to connect to Google Cloud services. When running within Google Cloud Platform environments 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.


  1. Create a service account and credentials.
  2. Set the environment variable.
export DATASTORE_CREDENTIALS=/path/to/json`
  1. Initialize the client.
require "google/cloud/datastore"

client =

Project and Credential Lookup

The google-cloud-datastore 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
  5. Discover project ID in credentials JSON

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

When running on Google Cloud Platform (GCP), including Google Compute Engine (GCE), Google Kubernetes Engine (GKE), Google App Engine (GAE), Google Cloud Functions (GCF) and Cloud Run, the Project ID and Credentials and are discovered automatically. Code should be written as if already authenticated.

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 google-cloud-datastore checks for project ID are:


The environment variables that google-cloud-datastore checks for credentials are configured on Google::Cloud::Datastore::Credentials:

  1. DATASTORE_CREDENTIALS - Path to JSON file, or JSON contents
  2. DATASTORE_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
require "google/cloud/datastore"

ENV["DATASTORE_PROJECT"]     = "my-project-id"
ENV["DATASTORE_CREDENTIALS"] = "path/to/keyfile.json"

client =


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

require "google/cloud/datastore"

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

client =

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-datastore.

If you are not running this client within Google Cloud Platform environments, you need a Google Developers service account.

  1. Visit the Google Cloud Console.
  2. Create a new project or click on an existing project.
  3. Activate the menu in the upper left and select APIs & Services. From here, you will enable the APIs that your application requires.

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

  4. Select Credentials from the side navigation.

    Find the "Create credentials" drop down near the top of the page, 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 click the pencil tool on the right side to edit the service account, select the Keys tab, and then select Add Key.

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


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