When the whales fly (or Twitter hiccups)

From time to time, the users of Twitter are unable to login on the official website.

Sometimes the screen below can be seen, sometimes just a timeout error. Interesting enough, after you refresh a couple of times, you are able to do whatever you were trying to do, and then never get this error until you login again.

http://twitter.com/503
http://twitter.com/503

There can be many reasons for which we see this error. From a simple overload to a distributed denial of service. Which we know that it happened on August 6, 2009 [1].
But, the most common reason is too many users(or services) are trying to access the Twitter services simultaneously. In this case, the servers behind the twitter.com domain are overloaded and are not able to access the required information to let you in. There is a corresponding HTTP error which is reported : 503 – Service (or server) not available.
But what is this error and why are we able to see it when the webservers are not available?
There’s a trick.

Any decent webserver reserves a certain amount of connections for this kind of messages. This error code can be served in the following circumstances:
– Too many connections simultaneously.
– There is no content anymore in the Root folder – usually a site upgrade.
– A load balancer (usually a normal http server with mod_proxy_balancer loaded) report this when no balancer member is able to serve the requests.

So, is this really the case with Twitter?
It may be… considering the fact that various sources report that Twitter has more than 200 million users.
In order to find out more about Twitter’s outages please read Wikipedia [1]

What to do when the whale flies?
Be patient.

Legend:
[1]. http://en.wikipedia.org/wiki/Twitter#Outages


© Copyright 2010 Sorin Mustaca, All rights Reserved. Written For: Sorin Mustaca on Cybersecurity


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