Production Kubernetes

Chapter 6. Service Routing

Service routing is a crucial capability of a Kubernetes-based platform. While the container networking layer takes care of the low-level primitives that connect Pods, developers need higher-level mechanisms to interconnect services (i.e., east-west service routing) and to expose applications to their clients (i.e., north-south service routing). Service routing encompasses three concerns that provide such mechanisms: Services, Ingress, and service mesh.

Services provide a way to treat a set of Pods as a single unit or network service. They provide load balancing and routing features that enable horizontal scaling of applications across the cluster. Furthermore, Services offer service discovery mechanisms that applications can use to discover and interact with their dependencies. Finally, Services also provide layer 3/4 mechanisms to expose workloads to network clients outside of the cluster.

Ingress handles north-south routing in the cluster. It serves as an entry point into workloads running in the cluster, mainly HTTP and HTTPS services. Ingress provides layer 7 load balancing capabilities that enable more granular traffic routing than Services. The load balancing of traffic is handled by an Ingress controller, which must be installed in the cluster. Ingress controllers leverage proxy technologies such as Envoy, NGINX, or HAProxy. The controller gets the Ingress configuration from the Kubernetes API and configures the proxy accordingly.

A service mesh ...