Facebook Opens Live Commenting To All - InformationWeek
Software // Social
11:27 AM

Facebook Opens Live Commenting To All

A company engineer details the behind-the-scenes development challenges in creating the new instant messaging-like feature.

Top 20 Apps For Managing Social Media
(click image for larger view)
Top 20 Apps For Managing Social Media

By 2014, people are expected to send 128 billion IMs worldwide per day, according to estimates by the Radicati Group. This year, the research firm predicts, users will send 76 billion, compared with 60 billion in 2010.

Before adding live comments, Facebook's infrastructure optimized more reads than writes, he said. But now the company "flipped the game," said Deeter. Because of this messaging feature, each page-load needs multiple writes, and each write of a comment requires a read.

"We realized that we were building something that was fundamentally backwards from most of our other systems," he said. "At Facebook, traditionally, writes are applied to one database and asynchronously replicated to databases across all regions. A good way to think of this approach is 'read locally, write globally.' Because of our unique situation, we settled on the completely opposite approach: 'write locally, read globally.'"

To accomplish this, Facebook deployed distributed storage tiers that exclusively handle writes locally, then less frequently collect information from the company's data centers to create the final result, said Deeter.

When users load their News Feeds via Facebook's Virginia data center, the system writes to a storage tier within that data center, recording the fact that users are viewing specific pieces of content and pushes new comments to those accountholders, he explained. As friends input comments, Facebook fetches viewership information from all its data centers, combines that information, and then pushes out those updates.

"In practice, this means we have to perform multiple cross-country reads for every comment produced. But it works because our commenting rate is significantly lower than our viewing rate," Deeter said. "Reading globally saves us from having to replicate a high volume of writes across data centers, saving expensive, long-distance bandwidth." Other members of the Facebook engineering team included Prasad Chakka, Adam Hupp, Elliot Lynde, Chris Piro, Tom Occhino, and Tom Whitnah. The effort, which began at Hackathon, required constant coordination between Facebook's front- and back-end engineers, said Deeter.

This is not the first marriage of social media and instant messaging. In 2009, for example, Google unveiled Wave, a communication and collaboration system that aims to be "what e-mail might look like if it were invented today." The service -- which Google made widely available in May 2010 -- gave users real-time IM communication and asynchronous email messaging. After underwhelming response, Google nixed Wave in August 2010.

2 of 2
Comment  | 
Print  | 
More Insights
Newest First  |  Oldest First  |  Threaded View
How Enterprises Are Attacking the IT Security Enterprise
How Enterprises Are Attacking the IT Security Enterprise
To learn more about what organizations are doing to tackle attacks and threats we surveyed a group of 300 IT and infosec professionals to find out what their biggest IT security challenges are and what they're doing to defend against today's threats. Download the report to see what they're saying.
Register for InformationWeek Newsletters
White Papers
Current Issue
2017 State of the Cloud Report
As the use of public cloud becomes a given, IT leaders must navigate the transition and advocate for management tools or architectures that allow them to realize the benefits they seek. Download this report to explore the issues and how to best leverage the cloud moving forward.
Twitter Feed
InformationWeek Radio
Archived InformationWeek Radio
Join us for a roundup of the top stories on InformationWeek.com for the week of November 6, 2016. We'll be talking with the InformationWeek.com editors and correspondents who brought you the top stories of the week to get the "story behind the story."
Sponsored Live Streaming Video
Everything You've Been Told About Mobility Is Wrong
Attend this video symposium with Sean Wisdom, Global Director of Mobility Solutions, and learn about how you can harness powerful new products to mobilize your business potential.
Flash Poll