Blog
Thoughts on engineering, design, and building great products.
The Lifecycle of a Pod: Phase, Condition and restartPolicy
Opens the deep-dive Pods section with something you read every day in kubectl get pods but rarely read closely: a pod's status. This article separates the three layers of status — the coarse phase, the detailed container state, and conditions as a checklist — then shows that phase is actually derived from container state plus restartPolicy. Four real pods illustrate Running, Succeeded, Failed and CrashLoopBackOff.
The Lifecycle of a Request: From kubectl apply to a Running Pod
The previous smoke test showed the cluster runs; this article traces a single apply command through each component we built, in chronological order, to see how they hand off to one another. More important than the sequence of steps is the model behind it: there is no conductor giving orders, just many independent loops all looking at one source of truth and pulling reality toward the desired state.
Smoke Test: The Whole Cluster Running Together
Every component is present; this article tests that they work together. We deploy a real application via a Deployment, expose it with a Service, call it by name and watch traffic spread evenly across replicas, use logs/exec/port-forward, then delete a pod to see the cluster self-heal. Each test shines a light on one piece we built throughout the series.
CoreDNS: Calling Each Other by Name in the Cluster
Pods can already talk by IP, but a pod's IP changes every time it's reborn, so no one hard-codes them. CoreDNS fills that gap: it runs as a workload right in the cluster, sits behind a Service at exactly the 10.32.0.10 that kubelet has been pointing pods at, and resolves Service names into ClusterIPs. This article deploys CoreDNS by hand — RBAC, ConfigMap, Deployment, Service — then tests a pod resolving both internal and external names.
Wiring Up Pod Networking by Hand: CNI bridge and VPC Routes
The previous theory article laid the groundwork; this one does the assembly. We write the CNI bridge + host-local config for each worker, add routes in the VPC route table so pod-to-pod across nodes works, then watch the two nodes finally flip to Ready. At the end we create two real pods on two different nodes and ping between them — each pod gets an IP from its node's range, and packets cross nodes without NAT.
The Kubernetes Network Model
Before wiring up pod networking in the next article, you need to understand what kind of network model Kubernetes demands: one IP per pod, every pod talking directly with no NAT. This article walks through the model's four foundational requirements, the four kinds of in-cluster communication, why pod-to-pod across nodes is the hard part, the two families of solutions (overlay and native routing), and where CNI fits — laying the groundwork for the hands-on wiring next.
kube-proxy: Turning a ClusterIP Into a Real Destination
A Kubernetes Service is a virtual IP — it isn't bound to any machine. kube-proxy is the component that turns that virtual IP into forwarding rules on each node, so traffic to a ClusterIP lands on a real pod behind it. This article installs kube-proxy in iptables mode on two workers, dissects the NAT chains it generates, then curls a ClusterIP directly to watch it work — all without pod networking yet.