Reason why facebook was down for 2hours
It was unfortunate ,Earlier today i tried logging in to my face book around 6 a.m ,i couldn’t, my fellow bloggers and journalist were busy telling us Facebook was down ,nobody care to tell the reason why?
Despite Lizard Squad, a group notorious for attention seeking antics online, claimed responsibility on Twitter for the outages.
After my research on the reason why facebook was down for 2hours ,I found out the truth:
An automated system for verifying configuration values ended up causing much more damage than it fixed.
Early today Facebook was down or unreachable for many of you for approximately 2.5 hours. This is the worst outage we’ve had in over four years, and we wanted to first of all apologize for it. We also wanted to provide much more technical detail on what happened and share one big lesson learned.
The key flaw that caused this outage to be so severe was an unfortunate handling of an error condition. An automated system for verifying configuration values ended up causing much more damage than it fixed.
The intent of the automated system is to check for configuration values that are invalid in the cache and replace them with updated values from the persistent store. This works well for a transient problem with the cache, but it doesn’t work when the persistent store is invalid.
Today we made a change to the persistent copy of a configuration value that was interpreted as invalid. This meant that every single client saw the invalid value and attempted to fix it. Because the fix involves making a query to a cluster of databases, that cluster was quickly overwhelmed by hundreds of thousands of queries a second.
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