2023-02-03 learning Express JS

[jerryschen31]

App and Routing https://expressjs.com/en/starter/basic-routing.html

[jerryschen31]

Route definition takes the following structure:

app.METHOD(PATH, HANDLER) app is an instance of express. METHOD is an HTTP request method, in lowercase. PATH is a path on the server. HANDLER is the function executed when the route is matched.

const express = require('express');
const app = express();
app.put('/user', (req, res) => {
  res.send('Got a PUT request at <URL-OF-THIS-SERVER>/user')
})

[jerryschen31]

To serve static files such as images, CSS files, and JavaScript files, use the express.static built-in middleware function in Express.

The function signature is: express.static(root, [options])

The root argument specifies the root directory from which to serve static assets. For more information on the options argument, see express.static.

For example, use the following code to serve images, CSS files, and JavaScript files in a directory named public:

app.use(express.static('public'))

Now, you can load (i.e., serve to the client) the files that are in the public directory:

http://localhost:3000/images/kitten.jpg
http://localhost:3000/css/style.css
http://localhost:3000/js/app.js
http://localhost:3000/images/bg.png
http://localhost:3000/hello.html

NOTE: For best results, use a reverse proxy cache to improve performance of serving static assets.

[jerryschen31]

Cache request results Another strategy to improve the performance in production is to cache the result of requests, so that your app does not repeat the operation to serve the same request repeatedly.

Use a caching server like Varnish or Nginx (see also Nginx Caching) to greatly improve the speed and performance of your app.

Use a load balancer No matter how optimized an app is, a single instance can handle only a limited amount of load and traffic. One way to scale an app is to run multiple instances of it and distribute the traffic via a load balancer. Setting up a load balancer can improve your app’s performance and speed, and enable it to scale more than is possible with a single instance.

A load balancer is usually a reverse proxy that orchestrates traffic to and from multiple application instances and servers. You can easily set up a load balancer for your app by using Nginx or HAProxy.

With load balancing, you might have to ensure that requests that are associated with a particular session ID connect to the process that originated them. This is known as session affinity, or sticky sessions, and may be addressed by the suggestion above to use a data store such as Redis for session data (depending on your application). For a discussion, see Using multiple nodes.

Use a reverse proxy A reverse proxy sits in front of a web app and performs supporting operations on the requests, apart from directing requests to the app. It can handle error pages, compression, caching, serving files, and load balancing among other things.

Handing over tasks that do not require knowledge of application state to a reverse proxy frees up Express to perform specialized application tasks. For this reason, it is recommended to run Express behind a reverse proxy like Nginx or HAProxy in production.