Backend

Note

There are no specific requirements for a Looker application. While the reference implementation using JavaScript and Express.js, any choice of language, framework and platform can be used. Looker provides pre-built SDKs in JavaScript/TypeScript, Ruby, Python, C#, Kotlin (Android) and Swift (iOS).

The Looker Data Application Reference Implementation is built in JavaScript and Express.js, to use a single language for the full stack. It serves these main purposes:

  1. Authentication services
    • Providing tokens, for both embedding content and making API calls
    • Creating signed URLs for embedded content
    • Updating embed user permissions
  2. Backend API examples
    • Running data queries from the backend to provide the client with data

Authentication

Creating signed URLs for embedding

A key step in the embed flow is to generate a signed URL, as explained in the reference docs. This url can be generated via the Looker API, or your application can do so. By convention, a Looker application provides an /auth endpoint. The full code for generating the signed URL itself is provided in \auth\auth_utils.js, which exports a createSignedURL function. Additional examples in Python, Ruby, Java, C# and PHP are available on the Looker GitHub repository.

Embed Secrets

To support embedding, you must configure a domain allowlist, and set an embed secret.

The Looker URL and embed secret should be accessed by your application as environment variables (see below). Alternatively, one can retrive signed iframe urls via the Looker API method create_sso_embed_url(body).

API Keys for backend API calls

For backend patterns, where you are accessing Looker's API from the application or server, you must provide the SDK with a Client ID and Secret, plus information about the Looker instance. These should be provided to your application as environment variables (see below)

Env variables required by backend

PBL_PORT=3000

LOOKERSDK_API_VERSION=4.0
LOOKERSDK_BASE_URL=https://your-instance.looker.com
LOOKERSDK_CLIENT_ID=xxxxxxxxxxxxxxxxxxxxxx
LOOKERSDK_CLIENT_SECRET=xxxxxxxxxxxxxxxxxxxxxx
# no protocol for this host
LOOKERSDK_EMBED_HOST=your-instance.looker.com
LOOKERSDK_EMBED_SECRET=xxxxxxxxxxxxxxxxxxxxxx