The selfie that changed the world, or at least Twitter, has been in the news for the past month. On March 2, 2014 the infamous Oscar selfie of Ellen and her celebrity friends broke a record of 2 million retweets before midnight the same night. That record was previously set by President Barack Obama, hugging first lady Michelle Obama after his 2012 re-election.
The selfie caused Twitter to crash for more than 20 minutes, also breaking the record for the longest crash of the social media site. Twitter was infamous for crashing in its early days (anyone remember “Fail Whale?”), so it’s no wonder the social media giant worked extra hard to completely prepare their website infrastructure before going public in November 2013. This included building their own load testing tool, Iago, in 2012.
If they built their own tool to perform their own load test, why did the selfie cause their site to crash? The Oscar selfie crash is a perfect example of what companies can easily overlook. Twitter did not test their users properly and their homegrown tool clearly doesn’t solve all of the their problems…their servers still crash.
So what is Iago and why did Twitter decide to make it? And what does that have to do with your decision to use homegrown tools versus vendor load testing tools? Don’t worry, we will tell you.
Twitter’s homegrown Load Testing Tool: Iago
Iago was created in June of 2012 by Twitter’s internal engineering team. According to Twitter, Iago is a load generator created to help the social media site test services before they encounter production traffic. Chris Aniszczyk, Head of Open Source at Twitter, said, “There are many load generators available in the open source and commercial software worlds, but Iago provided us with capabilities that are uniquely suited for Twitter’s environment and the precise degree to which we need to test our services.”
Basically their homegrown tool was completely customized for their platform alone – a very attractive aspect of developing your own tool.
The three attributes Twitter focused on in creating Iago were:
- High performance – Iago was designed to generate traffic in a precise and predictable way, to minimize variance between test runs and allow comparisons to be made between development iterations.
- Multi-protocol – Modeling a system as complex as Twitter can be difficult, but it’s made easier by decomposing it into component services. Once decomposed, each piece can be tested in isolation; which requires the load generator to speak each service’s protocol. Twitter has in excess of 100 such services, and Iago tests most of them using built-in support for the internal protocols Twitter uses.
- Extensible – Iago is designed for engineers. It assumes the person building the system will also be interested in validating performance. As such, the tool is designed from the ground up to be extensible – making it easy to generate new traffic types, over new protocols and with individualized traffic sources.
Why Twitter Couldn’t Handle Ellen’s Selfie
If we were to do the math, Iago was up and running for nearly two years before the Oscar selfie. What happened to their load testing tool?
There were two main reasons why Twitter crashed. First, the tweet Ellen posted was a picture. On Twitter, a tweet accounts for only 260 bytes of data while a picture on Twitter accounts for 33KB of data, almost 130 times as much as a tweet. Second, Twitter’s distributed server system was already at max capacity so the load taken on by the website couldn’t be distributed to any nearby servers.
Twitter made one major mistake contributing to the crash back in March: they didn’t anticipate and replicate real user activity. Most likely Iago wasn’t instructed to generate a load based on a picture being retweeted millions of times, thus Twitter didn’t know what to expect when the Oscars rolled around.
Homegrown Tool vs. Vendor Load Testing Solutions
Twitter was looking for a DIY homegrown solution because of their unique platform, and while most load testing tools seek to accomplish the same goal, there are always differences between tools. Here are some of the differences we see between homegrown and vendor-provided load testing tools.
Homegrown Tools Are Not For Everyone
Twitter’s tool has done well to help them improve the performance of the service, but continued service disruptions show that it isn’t perfect. A homegrown tool isn’t always the best solution, and most of the time, companies do not have the resources handy to completely build their load testing tool from scratch. If you are interested in learning more about vendor options, give us a call. We’re more than happy to help.