Production ready eBPF, or how we fixed the BSD socket API

As we develop new products, we often push our operating system - Linux - beyond what is commonly possible. A common theme has been relying on eBPF to build technology that would otherwise have required modifying the kernel. For example, we’ve built DDoS mitigation and a load balancer and use it to monitor our fleet of servers.

This software usually consists of a small-ish eBPF program written in C, executed in the context of the kernel, and a larger user space component that loads the eBPF into the kernel and manages its lifecycle. We’ve found that the ratio of eBPF code to userspace code differs by an order of magnitude or more. We want to shed some light on the issues that a developer has to tackle when dealing with eBPF and present our solutions for building rock-solid production ready applications which contain eBPF.

For this purpose we are open sourcing the production tooling we’ve built for the sk_lookup hook we contributed to the Linux kernel, called tubular. It exists because we’ve outgrown the BSD sockets API. To deliver some products we need features that are just not possible using the standard API.

• Our services are available on millions of Continue reading

Graceful upgrades in Go

The idea behind graceful upgrades is to swap out the configuration and code of a process while it is running, without anyone noticing it. If this sounds error prone, dangerous, undesirable and in general a bad idea – I’m with you. However, sometimes you really need them. Usually this happens in an environment where there is no load balancing layer. We have these at Cloudflare, which led to us investigating and implementing various solutions to this problem.

Coincidentally, implementing graceful upgrades involves some fun low-level systems programming, which is probably why there are already a bajillion options out there. Read on to learn what trade-offs there are, and why you should really really use the Go library we are about to open source. For the impatient, the code is on github  and you can read the documentation on godoc.

The basics

So what does it mean for a process to perform a graceful upgrade? Let’s use a web server as an example: we want to be able to fire HTTP requests at it, and never see an error because a graceful upgrade is happening.

We know that HTTP uses TCP under the Continue reading