Black Friday and Cyber Monday are right around the corner and it’s time to talk about stress testing.
Your site is going to get hammered unlike any other time of the year, and if you’re like most retailers in 2014 you’re hoping to go back into the black from a weaker fall retail season.
So what do you need to do to stay afloat?
There are plenty of services available to you but one I’ve used and particularly found useful was LoadImpact.com.
What are concurrent users?
Stress testing is usually measured by concurrent users, that is to say, how many requests are simultaneously being made to your server at any given moment. Now 100 concurrent requests does not equal 100 customers. Take this blog for instance, you are on the site, but you aren’t making any requests right now. The text from this blog has already loaded and is sitting cached on your machine where you are reading it. You would not be a concurrent user because you made the request a few minutes ago and no you are no longer asking for anything from this server.
How many concurrent users should I test for?
There is no one-size fits all number but there is a good formula to start. We are mainly concerned about your busiest time, right? So let’s think about that time frame, it should be an 8-10 hour window. Estimate how many orders you’ll be getting during that time, you can do this by looking at last year’s and multiplying by how much you’ve grown in the last year. If you don’t have historical data, take your busiest time this year and multiply that by 50%.
The formula for concurrent users is as follows:
(Estimated Orders / hours it spans) * 2 = Concurrent Users to test for
So let’s use some practice numbers:
Let’s say you get 500 orders during your busiest time, which spans 8 hours, your concurrent users are as follows:
(500 / 8) * 2 = 125
You should run a test for 125 or more concurrent users.
Hopefully, this will prepare you for a very fortuitous holiday shopping season!
Also, while you’re doing your load testing, make sure you keep your monitors and alerts up to date on Canary so if anything goes wrong, you’ll be the first one to find out.