The Node.js Runtime

Your Cloud Run function runs in an environment consisting of an operating system version plus add-on packages, language support, and the Functions Framework library that supports and invokes your function. This environment is identified by the language version, and is known as the runtime.

For information about runtimes in general, and to learn which Ubuntu version each Node.js runtime uses, see the Cloud Run functions execution environment.

To start building and deploying Cloud Run functions with Node.js, see the Quickstart.

To build and test your functions on your local system, see Run Functions with Functions Framework.

Select the runtime

Cloud Run functions supports several versions of Node.js, listed on the Runtime support page. You can select the preferred Node.js runtime for your function during deployment:

Execution environment

The execution environment includes the runtime, the operating system, packages, and a library that invokes your function.

Node.js 18 and newer versions use an execution environment based on Ubuntu 22.04. Versions earlier than Node.js 18 are based on Ubuntu 18.04. See Cloud Run functions execution environment for more information.

The library that invokes your function is the Node.js Functions Framework.

Source code structure

In order for Cloud Run functions to find your function's definition, each runtime has certain structuring requirements for your source code. See Writing Cloud Run functions for more information.

Specify dependencies

You can specify dependencies for your functions by listing them in a package.json file. For more information, see Specifying dependencies in Node.js.

NPM build script

By default, the Node.js runtime executes npm run build if a build script is detected in package.json. If you require additional control over your build steps before starting your application, you can provide a custom build step by adding a gcp-build script to your package.json file.

You can prevent your build from running the npm run build script by either:

  • Adding a gcp-build script with an empty value in your package.json file: "gcp-build":"".

  • Setting the build environment variable GOOGLE_NODE_RUN_SCRIPTS to the empty string to prevent all scripts from running.

Asynchronous function completion

When working with asynchronous tasks that involve callbacks or Promise objects, you must explicitly inform the runtime that your function has finished executing these tasks. You can do this in several different ways, as shown in the following samples. The key is that your code must wait for the asynchronous task or Promise to complete before returning; otherwise the asynchronous component of your function may be terminated before it completes.

Event-driven functions

Implicit return

  exports.implicitlyReturning = async (event, context) => {
    return await asyncFunctionThatReturnsAPromise();
  };

Explicit return

  exports.explicitlyReturning = function (event, context) {
    return asyncFunctionThatReturnsAPromise();
  };

HTTP functions

Node.js 

// OK: await-ing a Promise before sending an HTTP response
await Promise.resolve();

// WRONG: HTTP functions should send an
// HTTP response instead of returning.
return Promise.resolve();

// HTTP functions should signal termination by returning an HTTP response.
// This should not be done until all background tasks are complete.
res.send(200);
res.end();

// WRONG: this may not execute since an
// HTTP response has already been sent.
return Promise.resolve();

Use middleware to handle HTTP requests

Node.js HTTP Cloud Run functions provide request and response objects that are compatible with ExpressJS to make consuming HTTP requests simple. Cloud Run functions automatically reads the request body, so you will always receive the body of a request independent of the media type. This means that HTTP requests should be considered to have been fully read by the time your code is executed. The nesting of ExpressJS apps should be used with this caveat—specifically, middleware that expects the body of a request to be unread might not behave as expected.

Use ES Modules

ECMAScript modules (ES modules or ESM) are a TC39 standard, unflagged feature in Node version 14+ for loading JavaScript modules. Unlike CommonJS, ESM provides an asynchronous API for loading modules. It also provides a popular syntax improvement with import and export statements that can be used within a Cloud Run function (instead of require statements).

To use ESM within a Cloud Run function, you must declare "type": "module" within your package.json.

{
  ...
  "type": "module",
  ...
}

Then you can use import and export statements.