Microsoft has announced that it will be discontinuing its experimental support for WebAssembly System Interface (WASI) node pools in Azure Kubernetes Service (AKS) in May. The company is recommending two alternative approaches for users to migrate to, ensuring minimal disruption to their workflows.

The decision to sunset WASI node pools is not surprising, given the evolution of WASI on Kubernetes. The closure of the experimental support means that users will need to migrate to an alternate runtime to continue running their WASI workloads on AKS. Microsoft's recommended alternatives, SpinKube and wasmCloud, offer a way to add a new layer to the AKS platform, ensuring that users can continue running with minimal disruption.

The WASI node pools feature was dependent on the experimental Krustlet project, which used Rust to build WebAssembly-ready Kubelets. However, with the Krustlet project no longer being maintained, Microsoft had no choice but to change its approach to WebAssembly in AKS. Fortunately, AKS offers a managed way to work with Kubernetes, allowing it to support the wider Kubernetes ecosystem via standard APIs and offer alternative approaches to running WASI on its platform.

One of the recommended alternatives is SpinKube, a serverless computing platform that uses WASI workloads and manages them with Kubernetes. SpinKube has developed a shim for the standard Kubernetes container host, containerd, which allows users to run WASI workloads without needing to change the underlying Kubernetes infrastructure. Microsoft provides instructions on how to use SpinKube in AKS, and users can deploy it to existing AKS clusters, ensuring a smooth transition.

The other recommended alternative is wasmCloud, a CNCF project that offers a different architectural approach to running WASI workloads on AKS. wasmCloud requires a Helm chart to install the various components, and users need to start from scratch, rearchitecting their cluster and application for use with wasmCloud. While this approach requires more effort, it offers a unique way of building and running applications using WASI components.

The underlying philosophies of SpinKube and wasmCloud are very different, with SpinKube focused on quickly launching WASI-based functions and wasmCloud designed to host full-scale WASI-based applications. This diversity of approaches is beneficial for users, as it allows them to choose the right WASI platform for their needs.

The discontinuation of WASI node pools and the recommendation of alternative approaches is a significant development in the world of cloud computing and Kubernetes. As users explore the possibilities of WebAssembly, having multiple options for running WASI workloads on AKS is a welcome development. The flexibility and power of Kubernetes make it an ideal platform for building and managing distributed applications, and the availability of alternative approaches to running WASI workloads ensures that users can continue to innovate and experiment with this exciting technology.