How to simulate heavy traffic

This guide will walk you through how to simulate a large number of users accessing the website at the same time. This is useful for testing how the website performs under load.

Simple testing

Begin by installing autocannon, a tool for load testing HTTP servers. You can install it globally using pnpm:
bash
```
pnpm install -g autocannon
```
The development server is not suitable for realistic load testing, so you need to build and start the website first:
bash
```
pnpm build
pnpm preview
```
To run a load test, you need to decide which page you want to test. For example, to test the website's news page, you can use http://localhost:7777/news.
The following command starts the load test. It simulates 200 users accessing the news page as many times as possible for 20 seconds:
bash
```
autocannon -c 200 -d 20 --renderStatusCodes http://localhost:7777/news
```
Requests made by authenticated users often create more load on the server. If you need to test this, you can use the --headers option to send cookies or other headers. For example, to send a cookie with the request, you can use:
bash
```
autocannon -c 200 -d 20 --headers "Cookie":"authjs.session-token=..." http://localhost:7777/news
autocannon -c 200 -d 20 --headers "Cookie":"externalCode=..." http://localhost:7777/news
```
You may also want to send form data or other request information. For example, to send a POST request with form data, you can use:
bash
```
 autocannon -c 200 -d 20 --method POST --idReplacement --renderStatusCodes --body "ticketId=f47cdd7b-e347-4d28-a0d1-e0babcc650f3" --headers "Cookie":"externalCode=[<id>]" --headers "Content-Type":"application/x-www-form-urlencoded" http://localhost:7777/shop/tickets?/addToCart
```
Browsing the website normally and inspecting the requests using the browser's developer tools can help you identify the headers you need to send.

Programmatic usage

If you need to run load tests programmatically, you can use the autocannon module in your Node.js scripts. Here is an example script that simulates 300 users adding a ticket to the cart:

import autocannon from "autocannon";
import { randomBytes } from "crypto";

const base = "http://localhost:7777";
const path = "/shop/tickets?/addToCart";
const url = `${base}${path}`;
const ticket = "2f13d41b-67aa-4e06-84cf-e56633a5042a";
const ids = new Set();
const requests = 300;

const instance = autocannon(
  {
    url,
    connections: requests,
    amount: requests,
    timeout: 60,
    body: `ticketId=${ticket}`,
    method: "POST",
    setupClient: (client) => {
      const id = randomBytes(16).toString("hex");
      ids.add(id);
      client.setHeaders({
        "Content-Type": "application/x-www-form-urlencoded",
        Cookie: `externalCode=${id}`,
        origin: `${base}`,
        referer: `${base}/shop/tickets`,
        accept: "application/json, text/plain, */*",
      });
    },
  },
  finishedBench,
);

autocannon.track(instance, {});

function finishedBench(err, res) {
  console.log("finished bench", err, res);
  console.log("ids", ids.size);
}

Save this script to a file, for example load-test.js, and run it using node:

bash

node load-test.js

Considerations

You may prefer to use other tools like ab, wrk, or k6. autocannon is chosen here because it is easy to use, but note that it may have performance limitations.
You can adjust the number of users and duration as needed. Note that browsers may open multiple connections to the server, so the number of connections may not be the same as the number of users.
Be careful when running load tests on production servers. They can cause high CPU usage and slow down the server for other users. Additionally, sending a large number of requests to the server can be considered a DoS attack on the network.

How to simulate heavy traffic ​

Simple testing ​

Programmatic usage ​

Considerations ​

How to simulate heavy traffic

Simple testing

Programmatic usage

Considerations