LoadImpact

How many times can you get slashdotted?

Slashdotting (or "the slashdot effect") is a term coined by the site slashdot.com. It means that some big website/blog/newssite writes an article about you, causing tons of their visitors to take a sudden interest in your website, and causing your site to get overloaded with all the new visitors.

Slashdot has been around for a long time, but now there are many other sites that are big enough to cause a slashdot effect when they publish an article about something. One such site is the Russian web developer site habrahabr.ru where they call the effect the "habr effect".

We have had extensive experience with the "habr effect". We were mentioned on habrahabr.ru in february 2009 the first time, which caused some traffic to come our way. However, it seems habrahabr.ru has increased its number of readers substantially since then - they seem to have around 10x as much traffic today as they did early 2009, according to Alexa.

So, on wednesday they published an article about the importance of load testing as a way to avoid the habr-effect. They suggested people use Load Impact for their load testing (which we think is a splendid idea, of course). This resulted in a lot of people coming to our site to try out our load testing service.

This wouldn't have been a problem under normal circumstances, but an unknown bug in our frontend code had made it possible to start an unlimited number of load tests. We never noticed this under normal traffic conditions, but when several hundred new visitors arrived at the same time from habrahabr, and many of them tried to start a free load test, we suddenly found ourselves executing close to 200 load tests at the same time!

Our system was having problems: We had been habr'd (slashdotted) because of an article about how to avoid getting habr'd.

the effect the habrahabr article had on our (concurrent) site visitors

After some frantic bug-hunting, we found and fixed the frontend bug, and things started working much better.

Then we thought "hey, this was somewhat funny". We decided to write a blog article about the load testing people who got overloaded because of an article saying you should use their load testing service to avoid getting overloaded.

I wrote and published that article on our blog yesterday (thursday).

Today (friday) habrahabr picked it up and published a link to it. Guess what happened?

Yes, same thing (but a longer spike this time, so more traffic)

So today we have achieved something remarkable:

• Today, we were habr'd because of an article about being habr'd because of an article about how to avoid being habr'd!

All programmers out there will love the recursion, I bet.

Note: to be honest we didn't have much problem with the traffic today, even though it peaked at more visitors per hour than we normally get in a whole day.