David Wragg
Author Archives: David Wragg
- Home → Author's archive:
David Wragg
Unimog – Cloudflare’s edge load balancer
As the scale of Cloudflare’s edge network has grown, we sometimes reach the limits of parts of our architecture. About two years ago we realized that our existing solution for spreading load within our data centers could no longer meet our needs. We embarked on a project to deploy a Layer 4 Load Balancer, internally called Unimog, to improve the reliability and operational efficiency of our edge network. Unimog has now been deployed in production for over a year.
This post explains the problems Unimog solves and how it works. Unimog builds on techniques used in other Layer 4 Load Balancers, but there are many details of its implementation that are tailored to the needs of our edge network.
The role of Unimog in our edge network
Cloudflare operates an anycast network, meaning that our data centers in 200+ cities around the world serve the same IP addresses. For example, our own cloudflare.com website uses Cloudflare services, and one of its IP addresses is 104.17.175.85. All of our data centers will accept connections to that address and respond to HTTP requests. By the magic of Internet routing, when you visit cloudflare.com and your Continue reading
However improbable: The story of a processor bug
Processor problems have been in the news lately, due to the Meltdown and Spectre vulnerabilities. But generally, engineers writing software assume that computer hardware operates in a reliable, well-understood fashion, and that any problems lie on the software side of the software-hardware divide. Modern processor chips routinely execute many billions of instructions in a second, so any erratic behaviour must be very hard to trigger, or it would quickly become obvious.
But sometimes that assumption of reliable processor hardware doesn’t hold. Last year at Cloudflare, we were affected by a bug in one of Intel’s processor models. Here’s the story of how we found we had a mysterious problem, and how we tracked down the cause.
CC-BY-SA-3.0 image by Alterego
Prologue
Back in February 2017, Cloudflare disclosed a security problem which became known as Cloudbleed. The bug behind that incident lay in some code that ran on our servers to parse HTML. In certain cases involving invalid HTML, the parser would read data from a region of memory beyond the end of the buffer being parsed. The adjacent memory might contain other customers’ data, which would then be returned in the HTTP response, and the result was Cloudbleed.
But Continue reading
A Very WebP New Year from Cloudflare
Cloudflare has an automatic image optimization feature called Polish, available to customers on paid plans. It recompresses images and removes unnecessary data so that they are delivered to browsers more quickly.
Up until now, Polish has not changed image types when optimizing (even if, for example, a PNG might sometimes have been smaller than the equivalent JPEG). But a new feature in Polish allows us to swap out an image for an equivalent image compressed using Google’s WebP format when the browser is capable of handling WebP and delivering that type of image would be quicker.
CC-BY 2.0 image by John Stratford
What is WebP?
The main image formats used on the web haven’t changed much since the early days (apart from the SVG vector format, PNG was the last one to establish itself, almost two decades ago).
WebP is a newer image format for the web, proposed by Google. It takes advantage of progress in image compression techniques since formats such as JPEG and PNG were designed. It is often able to compress the images into a significantly smaller amount of data than the older formats.
WebP is versatile and able to replace the three main Continue reading