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Deadline to Die

Module 3: Networking & Discovery

🏗️ 1. The Manual Task: Static Service Discovery

In a traditional setup, services are identified by their static IP addresses or hardcoded entries in /etc/hosts.

The Problem:

  • Ephemeral IPs: Pods die and restart with new IPs.
  • Manual Toil: Updating the IPs of 50 backend pods in the frontend configuration manually every time they restart is impossible.

🌐 2. The Kubernetes Abstraction: Services & CoreDNS

A Service acts as a stable virtual IP (ClusterIP) for a set of Pods.

  • Stable Virtual IP: The IP address of the Service remains constant even if backend Pods change IPs.
  • Label Selectors: The Service automatically finds Pods that match specific labels (app: backend).
  • Integrated DNS: Kubernetes automatically creates a DNS record (http://backend-service) that resolves to the ClusterIP.
  • kube-proxy: The local node service that routes traffic from the virtual IP to the healthy backend Pods.