Blog
Thoughts on engineering, design, and building great products.
Requests, limits, QoS and the Downward API
Declaring requests and limits for a container isn't just about picking numbers. requests guide the scheduler, limits are kernel-enforced fences — CPU gets throttled, exceeding memory is an OOM kill. From those numbers Kubernetes sorts pods into three QoS classes that decide who gets killed first when the node runs out of RAM. This article tests all three QoS classes for real, an OOMKilled, and the Downward API for a pod to read information about itself.
Ephemeral containers and kubectl debug
Good production containers often have no shell — the leaner a distroless image, the fewer debugging tools, so kubectl exec is stuck. This article uses ephemeral containers: slip a tooling container temporarily into a running pod without restarting it or modifying its image. It digs into the semantics per the docs, then verifies all three modes of kubectl debug — attach to a running pod, copy the pod, and debug a node directly — on a real cluster.
Probes: liveness, readiness and startup
Article 18 left the Ready condition unexplained. Behind it sits the probe — how the kubelet asks a container three different questions: are you alive, are you ready for traffic, have you finished starting. This article separates the three kinds of probe per the docs, then verifies each with real pods: liveness kills and restarts, readiness removes the pod from a Service's endpoints, startup disables the other two until the app has time to start.
Init Containers and Sidecar Containers
A pod isn't just its main container. An init container runs preparation work to completion before handing off to the app; a sidecar container runs alongside the app for the lifetime of the pod. This article distinguishes the two, digs into the precise semantics from the docs — startup order, error handling, shutdown order — and verifies it with real pods on a v1.36 cluster.
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.