Multi-Tenant federated approach to resources brokering between Kubernetes clusters

Cloud computing has been a key technology in the last two decades, enabling the digital transformation that has shaped the current technology landscape. Within this trend, Kubernetes is currently the most prominent solution, promoting a model where applications are split into many loosely coupled components, each packaged as a Docker container and configured as a microservice. This paradigm effectively decouples the infrastructure - which can be scaled up or down on demand - from the application, which is then said to be cloud-native. Liquid computing deals specifically with the difficulties of a computing infrastructure that backs cloud-native workloads. Such an infrastructure is effectively "liquid" in that it can shift resources and applications from host to host. Liqo is an open source project launched at Politecnico di Torino that enables liquid computing on top of Kubernetes: with Liqo, Kubernetes clusters can join each other in a peer-to-peer fashion to seamlessly create a larger network, with each cluster still retaining full control over its resources. The goal of this thesis is to create a Multi-Tenant Kubernetes clusters federation, implementing a solution that also fits with the Gaia-X vision of federated cloud. The thesis aims to research and define brokering models for the Liqo ecosystem: service and resource brokers are an important player in a peer-to-peer topology, establishing trust, improving scalability and facilitating connections between providers and consumers. We propose three alternative models, among which we then further design and implement the Catalog approach, which best fits our use-case and allows to advertise and discover offers by different providers. The Catalog can be queried by any authenticated customer, and is also integrated with Liqo, through a Catalog Connector. As far as this last one, it is implemented as a Web server, which exposes a REST API and a WebSocket interface, it is managed by a graphical UI, where it is possible to create, update, delete and join offers, as well as to start a Liqo peering connection based on a stipulated contract. Part of the work has been integrated into the Liqo project, and is currently fully functional in the latest release, instead the Catalog Broker, the Catalog Connector and its UI have been developed as a Proof-of-Concept, and are available as a separate project on GitHub.