Adapting Kubernetes controllers to the edge: on-demand control planes using Wasm and WASI

TL;DR

This paper introduces a WebAssembly-based framework that enables on-demand, lightweight Kubernetes controllers at the edge, significantly reducing resource consumption compared to traditional approaches.

Contribution

It extends WASI to run Kubernetes controllers as Wasm modules, enabling on-demand activation and resource efficiency in constrained environments.

Findings

Achieves 64% memory reduction over container-based controllers

Enables on-demand activation of controllers, reducing resource usage

Runs controllers in a modified Wasmtime runtime with disk swapping

Abstract

Kubernetes' high resource requirements hamper its adoption in constrained environments such as the edge and fog. Its extensible control plane is a significant contributor to this, consisting of long-lived processes called "controllers" that constantly listen for state changes and use resources even when they are not needed. This paper presents a WebAssembly-based framework for running lightweight controllers on-demand, only when they are needed. This framework extends the WebAssembly System Interface (WASI), in order to run Kubernetes controllers as lightweight Wasm modules. The framework runs these Wasm controllers in a modified version of Wasmtime, the reference WebAssembly (Wasm) runtime, that swaps idle controllers to disk and activates them when needed. A thorough evaluation shows this framework achieves a 64% memory reduction compared to traditional container-based controller frameworks.