How do you enable millions of people to stay connected to their friends from their desktops, even when they are not using Facebook from their browsers? Late last year, we sat down to tackle this opportunity and today, we’re announcing Facebook Messenger for Windows.
As with most projects at Facebook, the team was small — two engineers and a designer — and our schedule was aggressive. The idea was simple: build an app that will run on your computer and deliver notifications and chat messages as they arrive from your friends. But to make the experience as compelling as possible, we focused on a few more key aspects:
- Simple and consistent with Facebook's UI — the interface should feel natural to people that are familiar with our website.
- Always ON and connected — when enabled, the app should turn on at system boot and stay connected at all times.
- Instant and reliable delivery of messages — chat messages and notifications should be delivered reliably without any delay.
With these key goals in mind, the team started coding toward the end of 2011. Less than two months later, we had built an initial alpha-quality product that combined all of the realtime communication features found in Facebook products like Ticker, Notifications, Friend Requests, and Chat, and rolled it out internally to employees for testing. After collecting feedback, we launched the product as a limited trial to about a small percentage of US users to test the app's effectiveness and the scalability of our server endpoints. Since then, we have polished the product, removed the last of the blocking bugs, and are ramping up for the full launch.
Reliable message delivery
To establish and maintain a persistent channel with our servers, we decided to use MQTT, which is the same real-time push channel that Facebook Messenger for iPhone and Android use. This is a very low-overhead protocol, and based on experience with the Messenger apps on phones, it has a proven track record of being extremely resilient and reliable. We keep one channel open at all times and use it to push down notifications, friend requests, Ticker stories and friends’ presence information. We also use the same channel to send and receive chat messages.
Installers and updaters
As with any client software, the first experience anyone has with the Messenger app is its installation flow. To make the installation flow as simple as possible, we used a small meta installer that takes care of downloading the right version of installer and performing the installation without any additional clicks. We learned a lot from building installers for Video Calling and reused much of the same technologies in Facebook Messenger. Our installation flow is optimized for each browser and walks people through the steps necessary to successfully download and install the software.
Another challenge with client software is how to keep it up to date. We want our users to receive bug fixes and updates without ever having to manually reinstall the app and ideally, this should just happen in the background without requiring any user interaction. Here, we used Google’s open source technology, Omaha, the same technology behind Google Chrome's auto updater. This technology helps us push bug fixes and updates reliably to everyone who has Facebook Messenger installed.
As we were developing Facebook Messenger for Windows, we found ourselves using the product for our day-to-day communication, replacing exchanges through the IRC client, which is what most Facebook engineers use internally. We're excited to continue improving the app and adding features, so stay tuned. We hope you have as much fun using this product as we had building it.
Designer: Rasmus Andersson
Engineering Manager: Ari Steinberg