Express

Express is a fast, unopinionated, minimalist web framework for Node.js. The App Platform’s serverless environment makes it easy to run apps without managing Node.js servers.

Getting Started#

Add your Express app to Edgio by running the following command in your project’s root directory:

1npm i -g @layer0/cli # yarn global add @layer0/cli
20 init

Running your app locally#

Test your app with the App Platform on your local machine by running the following command in your project’s root directory:

10 dev

Deploying#

Deploy your app to the App Platform by running the following command in your project’s root directory:

10 deploy

Overriding the default app location#

When you deploy your Express app to the App Platform, the Edgio CLI bundles your app as a single javascript file so that it can be run as a serverless function. By default, Edgio looks for your app in the following common locations:

• src/server.ts
• src/server.js
• src/app.ts
• src/app.js
• src/index.ts
• src/index.js
• server.js
• app.js
• index.js

If it cannot find one of these files, you can specify the path to the app in layer0.config.js:

1const {join} = require('path');
2
3// layer0.config.js
4module.exports = {
5  connector: '@layer0/express',
6  express: {
7    appPath: join(process.cwd(), 'path', 'to', 'app.js'),
8  },
9};

The file you specify in appPath should export an instance of an express app using export default or module.exports.

Serving Static Assets#

If your express app serves any static assets, you’ll need to add routes to your Edgio router configuration to serve them from the edge. For example, to serve all paths under /assets from dist/client/assets:

1// routes.js
2import {Router} from '@layer0/core';
3
4export default new Router()
5  // Prevent search engine bot(s) from indexing
6  // Read more on: https://docs.layer0.co/guides/cookbook#blocking-search-engine-crawlers
7  .noIndexPermalink()
8  .match('/assets/:path*', ({cache, serveStatic}) => {
9    cache({
10      edge: {
11        maxAgeSeconds: 60 * 60 * 365, // cache at the edge for one year
12      },
13      browser: {
14        maxAgeSeconds: 60 * 60 * 365, // cache in the browser for one year - only do this if you include hashes in your client asset filenames
15      },
16    });
17    serveStatic('dist/client/assets/:path*');
18  })
19  .fallback(({renderWithApp}) => renderWithApp()); // serve all unmatched URLs from express

Adding Additional Files Needed during SSR#

If your express app expects to be able to read files from the filesystem at runtime, for example an index.html template, you can ensure they are included in the app bundle that is deployed to App Platform’s serverless workers by adding the following to layer0.config.js

1module.exports = {
2  /* ... */
3
4  includeFiles: {
5    // Include index.html in the serverless bundle
6    'dist/client/index.html': true,
7  },
8};

Transpiling and TypeScript support#

Edgio will automatically transpile JavaScript and TypeScript source code for running on Node.js version 14. If you want to control how source files are compiled, you can transpile your app on your own and point your appPath config to the transpiled version of your app’s main entry point.

Bundling Options#

By default, Edgio uses ESBuild to transpile and bundle your application code. If you’re having difficulty fitting your app within the limit for serverless bundles, you can try bundling with ncc, which should produce smaller bundles, by adding the following to layer0.config.js:

1module.exports = {
2  express: {
3    bundler: '@vercel/ncc',
4  },
5};

Then add ncc to your app’s build dependencies:

1npm i -D @vercel/ncc@^0.34.0

Or, using yarn:

1yarn add --dev @vercel/ncc@^0.34.0

NCC produces a tree-shaken, bundle which includes your application code and all of its dependencies in a single file (written to .layer0/lambda/backends/index.js). NFT is also supported:

1module.exports = {
2  express: {
3    bundler: '@vercel/nft',
4  },
5};

Then add nft to your app’s build dependencies:

1npm i -D @vercel/nft@^0.21.0

Or, using yarn:

1yarn add --dev @vercel/nft@^0.21.0

NFT is similar to NCC, but it produces an exploded directory tree instead of including all of your code in a single file. We recommend trying ncc first.