KubeDay Japan 2024

There are many use cases for scheduling in the world, and we, SIG-Scheduling maintainers, regard extendability as crucial, and Kube-scheduler has two major ways to extend it, webhook and Golang SDK. However, these come with drawbacks - performance/extendability issues with webhook, and the need to rebuild and replace schedulers with Golang SDK. The proposed talk seeks to introduce our new solution to these challenges - a WebAssembly based extension. We’ll begin with a story about why custom schedulers are needed, and how existing extensions work. Then, we’ll get into why architecturally WebAssembly is a great fit for plugins, while also covering its challenges. You’ll hear about technical surprises implementing the plugin system in WebAssembly, such as sandbox limitations and programming concerns. When you leave this session, you will know first-hand how a complex WebAssembly project looks and feels, with concrete details of how WebAssembly fits into infrastructure extensibility.