GitHub uses MySQL to store its metadata: Issues, Pull Requests, comments, organizations, notifications and so forth. While git repository data does not need MySQL to exist and persist, GitHub’s service does. Authentication, API, and the website itself all require the availability of our MySQL fleet.
We serve a lot of diffs here at GitHub. Because it is computationally expensive to generate and display a diff, we’ve traditionally had to apply some very conservative limits on what gets loaded. We knew we could do better, and we set out to do so.
Recently we introduced GLB, the GitHub Load Balancer that powers GitHub.com. The GLB proxy tier, which handles TCP connection and TLS termination is powered by HAProxy, a reliable and high performance TCP and HTTP proxy daemon. As part of the design of GLB, we set out to solve a few of the common issues found when using HAProxy at scale.
Today we are announcing the open source release of octocatalog-diff: GitHub’s Puppet development and testing tool.
At GitHub we serve billions of HTTP, Git and SSH connections each day. To get the best performance we run on bare metal hardware. Historically one of the more complex components has been our load balancing tier. Traditionally we scaled this vertically, running a small set of very large machines running haproxy, and using a very specific hardware configuration allowing dedicated 10G link failover. Eventually we needed a solution that was scalable and we set out to create a load balancer solution that would run on commodity hardware in our typical data center configuration.