Putting five-year old smartphones through their paces might sound a little strange. Facebook is running its app on these devices for an important reason though. It wants to ensure everyone has the best Facebook experience possible, regardless of the device they own.
For people in emerging markets, obtaining a high-end modern smartphone is very difficult. Over the next few years, hundreds of thousands of people in Asia and South America will come online, the vast majority of them via low-end or aging Android smartphones. To ensure Facebook is accessible, the company has a server rack filled with handsets like the iPhone 4S and Samsung Galaxy Nexus, both launched in 2011.
“Guys in Brazil and Southeast Asia, they don’t have the cool new phone,” Ken Patchett, Facebook’s director of Western Data Center Operations, told CNET during a tour of the facility. Facebook’s Prineville data centre in Oregon is its oldest data centre but one that is continually expanding. It has undergone non-stop construction since its launch.
In total, Prineville holds over 2,000 phones, spread across 60 server racks of 32 devices each. Known as the Mobile Device Lab, the phones are controlled by servers and run continual automated tests of Facebook’s mobile apps, constantly monitoring for performance problems.
Each time a developer makes a code change to the Facebook, Facebook Messenger or Instagram apps, the update is immediately deployed to the phones. The servers begin to measure the performance of the new build, assessing important properties like news feed browsing speed and battery life. By studying the apps across dozens of smartphone models, Facebook can be confident they’ll perform well on the aging hardware.
The Mobile Device Lab has evolved considerably since Facebook’s earliest efforts to track device performance. The phones were moved to Prineville in March 2015 when they became a permanent automated testing stage. Before that, the handsets were placed on a plastic rack capable of holding 100 devices. The earliest version of the setup saw engineers use an old Android phone at their desks, alongside their primary device.
Mobile Device Lab represents app testing at its most thorough. Most tech companies run automated tests on a handful of popular devices using software emulators. Facebook decided that approach isn’t good enough. By running actual versions of its apps on real devices, Facebook can be sure its results are as indicative of real world performance as possible.
For all it’s achieved, the Mobile Device Lab is limited in one key respect though. Facebook is unable to test the performance of its apps on the limited 2G internet connections common in emerging markets, preventing it from seeing how they’ll degrade as network performance drops off.
Facebook is continuing to improve the Mobile Device Lab but there are currently no plans to add in checks for slow network connections. In the near future, it intends to open-source the Lab’s hardware and software, allowing other developers to test their apps on a range of devices as thoroughly as Facebook does.
