On Tuesday, 8 June, several popular websites like Twitch, Amazon, Spotify, Reddit, HBO Max, Quora, PayPal, Vimeo, the New York Times, BBC, Financial Times, UK government website, and a few others, were reported to be facing an outage due to a possible glitch at Fastly, a popular CDN provider. Fastly has confirmed issues with its CDN services and says that it is investigating the matter. But what is a CDN, and why did it impact so many global websites?
What is a CDN?
A Content Distribution Network (CDN) is a network of servers/data centers distributed across the globe that helps highly trafficked websites keep up with the constant demand for data. A CDN does this by offloading some of this load from the website’s primary servers. For instance, sending all the images that make up a web page to millions of users can be a demanding task and easily overwhelm a small group of servers. A CDN can act as a middle-man, sending these images directly to the user without the website’s own servers coming into play, thus improving response time. This is known as “caching.”
Why did so many websites go down together?
Fastly – a global CDN provider to some of the world’s biggest websites – acknowledged an outage just before 10:00 UTC, which caused several websites to go down. Fastly’s network spans the globe and aggregates traffic for multiple websites. When a part of a CDN goes down, it affects any websites served by that part. For instance, Fastly has five cities with a current or planned presence (caching server infrastructure) in India. If any or all of these servers went down, websites using Fastly’s CDN would appear slower or inaccessible to users in India.
Such outages can be isolated or affect traffic globally, depending on how severe.
What’s the status of these websites now?
Fastly responded to the outage and rolled out a fix by 10:57 UTC. According to their status page, Fastly customer websites would continue to see “increased origin load” as the services came back online. This means that when there’s no middle-man caching images and assets, requests from millions of users will go directly to a website’s main servers, possibly slowing down response.
At the time of writing, affected websites such as Twitch, Amazon, Spotify, Reddit, HBO Max, and Quora are accessible to users in India.