Mixed-Runtime Pod Networking for Kubernetes-Based Edge Computing

In recent years, microservice-based applications have shifted towards cloud-edge computing, taking advantage of green energy, lower latencies, and local computational resources. Simultaneously, various alternatives to containers, such as unikernels and WebAssembly, have emerged and are gradually being adopted by container-based orchestration software such as Kubernetes. However, solutions that integrate such alternatives are not generic: they only integrate a single specific non-container option, and generally do not allow for mixed-workload pods with both container and non-container workloads. Importantly, no solution is currently capable of integrating mixed-workload pods with all the features of pod networking as standardized by Kubernetes. This article presents a generic, runtime-agnostic solution which provides mixed-workload pods with all the standard behavioral features of pod networking. The core functionality of the proposed solution is sub-pod networking, which sets up small independent subnets for each pod rather than providing them a single IP address, and which is based on eBPF programs for efficient and secure traffic processing. The architecture is implemented in Feather, a Kubernetes-compatible orchestration agent which supports both containerd and OSv unikernels, and evaluations show that the end-to-end latency overhead of the implementation for various types of network traffic ranges from just 22μs to 200μs, and scales predictably with the number of non-container workloads in a pod. Additionally, the implementation has no significant memory overhead, and CPU overhead is 2Gbps to 6.4Gbps per percentage of a single core, depending on runtime and evaluation scenario.