NextJS Load Test

Overview

In this guide, we'll walk through creating a load test for a Next.js website using Locust, and running it with LoadForge. This specific test is able to used with any Javascript based site (next, nuxt, react, etc) as it automatically crawls URLs on the site and uses those in the load test.

Prerequisites

Ensure you have:

• Very basic understanding of Python.
• Have set up a LoadForge account.
• Have added and verified your Host for testing

Using BS4

LoadForge instances come pre-provisioned with many helpful tools, including beautifulsoup4, which we use for parsing html content in this test. You can install it yourself locally if you can busy developing your test still with the following command:

pip install locust beautifulsoup4

Creating Your Test File

The example below demonstrates a user that crawls a webpage, discovering and loading linked pages and static content (like images, CSS, JS files). You can paste this locustfile directly into LoadForge to test your site.

from bs4 import BeautifulSoup
from locust import HttpUser, task, between

class WebsiteUser(HttpUser):
    wait_time = between(1, 2.5)
    
    def on_start(self):
        self.crawl("/")
    
    def crawl(self, path):
        response = self.client.get(path, name="[Page] "+path)
        if response.status_code == 200:
            soup = BeautifulSoup(response.text, "html.parser")
            
            # Discover linked pages
            links = [a["href"] for a in soup.find_all("a", href=True)]
            for link in links:
                self.crawl(link)
            
            # Load static content (img, css, js)
            resources = [(link["href"], "CSS") for link in soup.find_all("link", href=True)]
            resources += [(script["src"], "JS") for script in soup.find_all("script", src=True)]
            resources += [(img["src"], "IMG") for img in soup.find_all("img", src=True)]

            for resource, res_type in resources:
                self.client.get(resource, name=f"[{res_type}] {resource}")

    
    @task(1)
    def load_homepage(self):
        self.client.get("/")

Notes on the script

• on_start: Initiates crawling the homepage once per simulated user.
• crawl: A recursive method making GET requests to paths, discovering and loading other linked resources.
• @task(1): Simulates users continually loading the homepage.

Conclusion

This guide provided a basic setup for load testing a Next.js website, crawling, and discovering links/resources. Ensure to optimize and adjust your locustfile based on real-world user interactions, website structure, and testing objectives.

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