WebAssembly Orchestration in the Context of Serverless Computing

Recent WebAssembly advancements including better programming language support and the introduction of both the WebAssembly System Interface, and the WebAssembly Component Model, have transformed it from primarily a client-side technology to a server-side one as well. The advantages associated with WebAssembly, such as cross platform portability, small software artifacts sizes, fast start up times, and per execution isolation make it a good fit for serverless scenarios. While there are existing initiatives for using WebAssembly in such serverless contexts, orchestration is still an open question. To overcome this issue, we present a way for extending Kubernetes, allowing it to orchestrate natively executed WebAssembly modules, in addition to containers. We describe an extension to an existing WebAssembly software shim for containerd and a new Kubernetes WebAssembly operator. Benchmarking results from the proposed solution obtained using 9 serverless functions packaged both as WebAssembly modules and OpenFaaS functions running in containers, show that WebAssembly has clear advantages for frequently executed serverless functions which require elasticity. WebAssembly functions enjoy two times faster deployment times and at least an order of magnitude smaller artifact sizes while still offering comparable execution performance. However, when it comes to sustained performance for long running serverless functions with processor intensive workloads, containers are the preferred choice, compensating for the increased cold start times with faster execution times.