Defining and Improving Website Load Testing
Before launching a website, you want to be sure it can handle the expected level of activity without slowing down or crashing. Load testing allows you to see how your site will perform under "real world" conditions and helps you identify areas where changes need to be made to avoid unexpected problems when the site goes live.
What is load testing?
As a type of performance testing, a load test is defined as "the process of putting demand on a system and measuring its response." By placing your website and its supporting server under "ordinary stress" and observing the outcomes, you get a good idea of whether or not it will work the way it's supposed to when accessed by a reasonable number of users.
Unlike stress testing, in which a system is pushed to its limits until it fails, load tests only push hard enough to demonstrate the effects on performance at the intended capacity or just short of an overload. Taking this step down from a stress test reveals the point at which your website stops providing a good user experience instead of simply telling you what it takes to cause a crash.
There are two types of load testing to consider when building your site:
- Endurance, also called longevity, measures performance during constant, moderate-level work.
- Volume determines how well the system can handle heavy work for short periods.
Both tests begin with realistic scenarios involving actions you expect actual users to take as they interact with your site. From these models, you can determine:
- The maximum capacity of the server.
- Whether the underlying infrastructure offers sufficient support.
- How many users the site can handle at a time.
- How long good performance can be maintained under the largest expected load of users.
To discover these limitations and understand what changes must be made to scale up the load your website can handle, you need to understand how to set up and perform a proper load test.
How does load testing work?
You may have created a list of goals or objectives for your website before you began designing. This list is useful for load testing because it defines what you expect the finished site to do and how you want users to interact with it. When performing a load test, you want to focus on what's required to achieve the intended outcomes.
For example, if you're creating an ecommerce site and will be offering a discount to celebrate the launch, you want to be sure the server can handle the influx of customers driven to the site by your pre-launch campaigns. This scenario forms the basis of your test case, a hypothetical situation in which users' expected actions are carried out and the resulting effects on load are measured.
Although each case is unique, there are some common metrics to monitor when testing load:
- Latency, or how fast the server responds to client requests.
- Throughput, defined as the number of requests a server can handle during a given period of time.
- The percentage of the CPU, memory, and network utilized.
- User load, a value denoting the maximum number of simultaneous users the server can handle.
Pay attention to each metric as you run your tests, and make note of the points at which it becomes impractical for the server to accept more requests. This is likely to happen before the full capacity of the server is reached, and a common sign is an increase in latency resulting in slow page load times.
Your goal is to discover the point at which the site stops functioning in a user-friendly manner. To determine this, start your test with a small load and gradually increase until the user experience begins to suffer. Beginning with a low number of users ensures you don't miss any bottlenecks or errors arising as the load grows. Instead, you get clear data showing how your site performs in a variety of situations and can pinpoint the areas you need to fix prior to going live.
Why is load testing important?
No matter what you want to accomplish with your website, you need to know its underlying infrastructure is strong, stable and reliable enough to support a reasonable number of users. Load tests are performed in a safe environment before your site is seen by the public, so you can create, run and monitor as many test cases as necessary without affecting live pages.
A well-executed load test in which the proper performance metrics are monitored shows you any existing glitches or bugs with the potential to disrupt site performance and negatively affect the user experience. It also reveals elements slowing down normal processes or creating situations in which performance suffers while waiting for a response from the server. If you discover your server lacks the capacity to handle the amount of traffic your site is likely to draw, you'll need to consider taking steps to reduce the load or investigate ways to scale up the hardware. Learn more about things to consider when running a high traffic website.
Because building and launching a website already takes a great deal of work, you may be tempted to skip load testing and fix any issues later. However, doing so can lead to a variety of problems, the solutions for which may take longer than the tests designed to prevent them in the first place. When you take the time to run load tests, you benefit by:
- Avoiding unnecessary downtime
- Ensuring visitors can always access the information they want
- Preventing loss of ecommerce revenue
- Maintaining a reputation of reliability with visitors and customers
- Preserving the expected page load speeds
- Increasing the amount of time visitors spend on the site
- Always being able to follow through on promised promotions or perks
Everything you discover during a load test can be used to develop a long-term performance management strategy. With knowledge of potential performance problems and their causes, you can implement big changes before you launch and make further tweaks along the way to continually improve the user experience. After applying these tweaks, be sure to run your tests again to see if the problems have been fixed.
Top tools for load testing
It's easier to perform comprehensive load tests if you use a program to automate the process. You can do the tests manually, but these tools save time and effort while still giving you the information necessary to improve site performance:
Apache JMeter is a Java-based open source program suitable for many different types of load testing
LoadComplete creates realistic test cases, automates the testing process and provides detailed reports on key metrics
NeoLoad is useful for simulating realistic user activity in test environments
SmartMeter uses JMeter as its core and auto-generates reports, making it a simple and practical solution for your load testing needs
WebLOAD offers a free version of professional-quality testing software with the capacity to handle enterprise-level systems
Tips for reducing load
As the number of users accessing your site increases, the supporting server is asked to handle more and more requests. Called the origin server, this is the main infrastructure on which your entire site relies. Once it hits capacity, your site can't support any more users without either suffering serious performance problems or shutting down entirely.
How can you scale up without investing in a server with more capacity? Try these tactics to reduce the load on the existing server and allow your site to handle more visitors:
- Use a content delivery network to store static content on edge servers around the world. This helps reduce the load on your origin server while simultaneously improve page speed.
- Compress images for web use with a tool such as Optimus.
- Prevent others from hotlinking files or images from your site.
- Host large files with third party services, such as Dropbox or Google Drive.
- Clean up code by eliminating unnecessary notes and white space.
- Make use of caching tools to minimize the number of times content is loaded from scratch.
Making these changes cuts down on the number of requests sent to the origin server and reduces the amount of bandwidth necessary to deliver a high quality user experience. You'll not only increase the amount of traffic your site can handle but also speed up page load speeds so that content remains easily accessible even during the busiest times.
When you perform a series of load tests prior to a website launch, you help to safeguard against embarrassing problems like slow load times, errors and crashes. Knowing what the server can handle before opening the site up to the first influx of real traffic allows you to make the necessary adjustments to reduce server load and improve performance. Users get the experience they expect, and you enjoy all the perks of increased site traffic and higher levels of engagement.