Serving Static Files

In addition to handling dynamic requests, applications often need to serve additional static files such as JavaScript, images, and CSS. The standard environment allows you to decide how to serve static content for your application. You can serve static content directly from your application, host it on a GCP option like Cloud Storage, or use a third-party content delivery network (CDN).

Hosting your static site on App Engine can cost less than using a traditional hosting provider, as App Engine provides a free tier.

Serving files from App Engine

To serve static files for Node.js in the standard environment, you define the handlers in your app.yaml file using either the static_dir or static_files elements.

Configuring your static file handlers

To configure your app to serve the ./public directory from the /static URL, you define a handler in your app.yaml file.

The following demonstrates how to serve the static files of a sample app's ./public directory. The template for this app's index.html page instructs the browser to load the main.css file, for example:

<link type="text/css" rel="stylesheet" href="/static/css/main.css">

The ./public directory is defined in the static_dir element of the project's app.yaml file:

handlers:
  - url: /favicon\.ico
    static_files: favicon.ico

  - url: /static
    static_dir: public

  - url: /.*
    secure: always
    redirect_http_response_code: 301
    script: auto

The handlers section in the above example includes two handlers for URLs. When App Engine receives a request for a URL beginning with /static, it maps the remainder of the path to files in the ./public directory. If an appropriate file is found in the directory, the contents of that file are returned to the client. All other URLs match the /.* pattern, and are handled by your app.

URL path patterns are tested in the order they appear in app.yaml, therefore the pattern for your static files should be defined before the /.* pattern. For more information, see the app.yaml reference.

Serving files for local development

Most web frameworks include support for serving static files, which you can use to serve files locally during development.

In the following example, the app uses the express.static middleware to serve files from the ./public directory to the /static URL. Specifically, the example app is serving a stylesheet that is located in ./public/css, from the URL /static/main.css.

'use strict';

const express = require('express');
const app = express();

app.set('view engine', 'pug');

// Use the built-in express middleware for serving static files from './public'
app.use('/static', express.static('public'));

app.get('/', (req, res) => {
  res.render('index');
});

// Start the server
const PORT = process.env.PORT || 8080;
app.listen(PORT, () => {
  console.log(`App listening on port ${PORT}`);
  console.log('Press Ctrl+C to quit.');
});

The view refers to /static/main.css.

doctype html
html(lang="en")
  head
    title Static Files
    meta(charset='utf-8')
    link(rel="stylesheet", href="/static/main.css")
  body
    p This is a static file serving example.

Other Node.js frameworks, such as Hapi, Koa, and Sails typically support serving static files directly from the app. Refer to their documentation for details on how to configure and use static content.

Serving files from GCP

You also have the option of using Cloud CDN or another GCP storage service like Cloud Storage.

Serving files from Cloud Storage

Cloud Storage can be used to host static assets for dynamic web apps. The benefits of using Cloud Storage instead of serving directly from your app include:

  • Cloud Storage essentially works as a content delivery network. This does not require any special configuration because by default any publicly readable object is cached in the global Cloud Storage network.
  • Your app's load will be reduced by offloading serving static assets to Cloud Storage. Depending on how many static assets you have and the frequency of access, this can reduce the cost of running your app by a significant amount.
  • Bandwidth charges for accessing content can often be less with Cloud Storage.

You can upload your assets to Cloud Storage by using the Cloud SDK or the Cloud Storage API.

Example of serving from a Cloud Storage bucket

This simple example creates a Cloud Storage bucket and uploads static assets using Cloud SDK:

  1. Create a bucket. It's common, but not required, to name your bucket after your project ID. The bucket name must be globally unique.

    gsutil mb gs://<your-bucket-name>
    
  2. Set the ACL to grant read access to items in the bucket.

    gsutil defacl set public-read gs://<your-bucket-name>
    
  3. Upload items to the bucket. The rsync command is typically the fastest and easiest way to upload and update assets. You could also use cp.

    gsutil -m rsync -r ./static gs://<your-bucket-name>/static
    

You can now access your static assets via https://storage.googleapis.com/<your-bucket-name>/static/....

For more details on how to use Cloud Storage to serve static assets, including how to serve from a custom domain name, refer to How to Host a Static Website.

For more information on how to use the Cloud Storage API to dynamically upload, download, and manipulate files from within your app, see Using Cloud Storage.

Serving from a third-party content delivery network

You can use any external third-party CDN to serve your static files and cache dynamic requests but your app might experience increased latency and cost.

For improved performance, you should use a third-party CDN that supports CDN Interconnect.

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App Engine standard environment for Node.js docs