Scores of popular websites, apps and news outlets worldwide were unavailable for nearly an hour early Tuesday after an outage at Fastly, a major content delivery service.
During the outage, web users – including readers of USA TODAY – received error messages such as “Error 503 Service Unavailable” when trying to access sites. The outage began shortly before 6 a.m. EDT and recovery started less than an hour later.
Fastly CEO Joshua Bixby told the Wall Street Journal Tuesday that the outage was not caused by an outside attack, as in the hacker ransomware attack on Colonial Pipeline on May 7.
Instead, Fastly cited a technical issue and said a fix had been applied, the Associated Press reported.
In a message posted to Twitter at 7:09 a.m. EDT, Fastly said “We identified a service configuration that triggered disruptions across our POPs globally and have disabled that configuration. Our global network is coming back online.”
Still confused? Here’s what that means:
What are CDNs?
Fastly is a cloud-based content delivery network or CDN. Websites, apps, and other companies use CDNs to move content around the world, reducing access time for users. CDNs carry more than half of the internet’s traffic, says Akamai, a CDN and cloud service company.
CDNs describe themselves as internet intermediaries. A simplified version of the process:
- A website wants to serve content such as a webpage, video or image, and sends it to a CDN.
- The CDN copies the content to edge servers across the network.
- The copy process is called caching. Cached information can be rapidly retrieved and is stored on a server for a set period of time.
- The servers are clustered at locations strategically sited around the world. The are known as points of presence or POPs.
- When a user seeks content—by typing a URL into a web browser for example—the CDN sends it from the closest edge server. Imperva.com says an appropriate PoP is chosen based on regional internet traffic patterns.
CDNs say the benefits are:
- A reduction in the physical travel distance for a content request.
- Less time between asking for a web page and having the page load on a device.
- A decrease in bandwidth costs.
How do CDNs work?
Let’s take a look at how this works, using the very USA TODAY website or app you are viewing this story on in a simplified example:
Some joke that the internet is a series of tubes, but that’s fairly accurate. There are wires in tubes everywhere that connect physical computers together, forming the net.
You, the user or client, make a request to download a file. That might look like a URL that you type into a web browser. Or the link you clicked that brought you to this page.
A website is mostly a collection of files that your computer needs to download from a server.
In our simple example, your request goes up to a web server, a machine sitting somewhere. We used to rely on physical racks in our server room in the basement. Now, most of our servers are virtual, but we’ll save an explanation of virtualization and cloud infrastructure for another day.
This web server is our origin server, the place where the files originate from.
If a valid request, the server will serve you those files to you. Your computer downloads it as the data is sent over the internet to your computer.
But files can be big, and your computer might be physically far away from the server. And you might want to request a website or file over and over, and downloading it repeatedly is slow and costly.
This is where caching comes in. It’s a concept where the last seen copy of a file or piece of data is saved for easy retrieval.
It can be pictured as the layers of an onion, protecting the central programs and computers from experiencing too much stress.
One of the most important forms of caching is the content delivery network.
A content delivery network is what it sounds like: a collection of thousands of web servers that hold the most recent copies of websites, files, and application data so that users can download files and do things faster.
Companies like Akamai and Fastly maintain thousands of edge servers in points of presence all over the world. These are close to where you are, even on cell towers. And once one person visits a version of a website, they save a copy there for all subsequent users.
So, unless you are the first person in your area to read this USA TODAY article, it’s likely being served to you by an edge server in a CDN.
During events like today’s outage some edge servers or the entire the CDN may no longer function, so everyone has to go back to the origin server. This causes major bottlenecks as servers get overloaded. Meanwhile, engineers rush to react to the influx of traffic and stabilize systems.
Examples of sites impacted by the outage
USA TODAY, New York Times, CNN, Guardian, BBC, Financial Times, Le Monde
Youtube, Instagram, Twitter, HBO Max, Reddit, Spotify, Twitch, Stack Overflow, Hulu, Quora, Vimeo, Stripe
Amazon, PayPal, Shopify, Etsy
SOURCE USA TODAY Network reporting and research; Associated Press; Reuters; Fastly.com; Akamai; imperva.com
Mitchell Thorson and Katie Vogel contributed to this report.