Facebook experienced a technical glitch lasting a few hours on Thursday, which resulted in the longest outage in four years, says the social networking site. The fault was traced to a flawed modification made by Facebook in a system that is activated whenever invalid data is found. The system itself was somehow deemed invalid, resulting in a feedback loop that overwhelmed the site's database cluster.

Engineers have since brought the site up again by turning off the automated system and essentially restarting the site. So while the site is operating as usual now, engineers are still working on ways to modify and re-enable the system without triggering a reoccurrence.

If anything, this outage highlights the inherent challenges in attaining perfect uptime for massive and constantly updated sites, even in the face of virtually limitless resources. For now, Robert Johnson, director of software engineering at Facebook wrote that "We apologize again for the site outage, and we want you to know that we take the performance and reliability of Facebook very seriously."

For more on this story:
- check out this article at CBS News
- check out this article at Computerworld

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