Overview

Overview

Services are agents which connect Pods together or provide access outside of the cluster. The Pod serves the expected resource using an Endpoint object.

Each Service can be exposed internally or externally to the cluster. A Service can also connect internal resources to external resources.

The kube-proxy agent watches the Kubernetes API for new services and endpoints being created on each node. It opens random ports and listens for traffic to the ClusterIP:Port, and redirects the traffic to the randomly generated service endpoints.

Services provide automatic load-balancing, matching a label query. While there is no configuration of this option, there is the possibility of session affinity via IP. Also, a headless service, one without a fixed IP nor load-balancing, can be configured. Labels are used to determine which Pods should receive traffic from a service (Service Update Pattern).

Unique IP addresses are assigned and configured via the etcd database, so that Services implement iptables to route traffic, but could leverage other technologies to provide access to resources in the future.