Kubernetes: Up and Running, 2nd Edition

Chapter 7. Service Discovery

Kubernetes is a very dynamic system. The system is involved in placing Pods on nodes, making sure they are up and running, and rescheduling them as needed. There are ways to automatically change the number of Pods based on load (such as horizontal Pod autoscaling [see “Autoscaling a ReplicaSet”]). The API-driven nature of the system encourages others to create higher and higher levels of automation.

While the dynamic nature of Kubernetes makes it easy to run a lot of things, it creates problems when it comes to finding those things. Most of the traditional network infrastructure wasn’t built for the level of dynamism that Kubernetes presents.

What Is Service Discovery?

The general name for this class of problems and solutions is service discovery. Service-discovery tools help solve the problem of finding which processes are listening at which addresses for which services. A good service-discovery system will enable users to resolve this information quickly and reliably. A good system is also low-latency; clients are updated soon after the information associated with a service changes. Finally, a good service-discovery system can store a richer definition of what that service is. For example, perhaps there are multiple ports associated with the service.

The Domain Name System (DNS) is the traditional system of service discovery on the internet. DNS is designed for relatively stable name resolution with wide and efficient caching. It is a great system ...