The latest articles on DEV Community by Tomek (@jural). https://dev.to/jural https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.us-east-2.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F4010150%2F2839f39b-551a-4c76-8f79-7f8877124edb.png https://dev.to/jural en Tomek Tue, 30 Jun 2026 23:04:49 +0000 https://dev.to/jural/kubernetes-probes-readiness-vs-liveness-vs-startup-and-how-a-wrong-setup-can-restart-your-whole-2aj2 https://dev.to/jural/kubernetes-probes-readiness-vs-liveness-vs-startup-and-how-a-wrong-setup-can-restart-your-whole-2aj2 <p>Most explanations of Kubernetes health probes are text and diagrams. I tried to explain them in a different way — with an interactive, step-by-step animation — and this is a short text version of it.</p> <h2> The three probes, in one line each </h2> <ul> <li> <strong>readiness</strong> — decides if the pod gets traffic. If it fails, Kubernetes removes the pod from the Service endpoints. The container is <strong>not</strong> restarted.</li> <li> <strong>liveness</strong> — decides if the container is restarted. If it fails, the kubelet <strong>restarts</strong> the container.</li> <li> <strong>startup</strong> — protects slow-starting containers. While it runs, liveness and readiness are held off, so a slow app is not killed before it is ready.</li> </ul> <p>The common mistake is treating readiness and liveness as the same "is it healthy?" check. They are not — one moves traffic, the other restarts the process.</p> <h2> How a wrong setup becomes an outage </h2> <p>The dangerous case: a <strong>liveness</strong> probe that checks a slow or shared dependency.</p> <p>A traffic peak makes that dependency even slower. The liveness probe then fails on <strong>all replicas at the same time</strong>, and Kubernetes restarts the whole deployment in a loop. So one slow dependency becomes a full outage — when readiness would have been the safer choice.</p> <p>This is only one of several setups that can cause it.</p> <h2> The interactive version </h2> <p>Here you can move a pod through the probe states and watch what happens each time (this GIF is one scene):</p> <p><a href="https://media2.dev.to/dynamic/image/width=800%2Cheight=%2Cfit=scale-down%2Cgravity=auto%2Cformat=auto/https%3A%2F%2Fdev-to-uploads.s3.us-east-2.amazonaws.com%2Fuploads%2Farticles%2Fnlkhkw6dphiuar6r8u6i.gif" class="article-body-image-wrapper"><img src="https://media2.dev.to/dynamic/image/width=800%2Cheight=%2Cfit=scale-down%2Cgravity=auto%2Cformat=auto/https%3A%2F%2Fdev-to-uploads.s3.us-east-2.amazonaws.com%2Fuploads%2Farticles%2Fnlkhkw6dphiuar6r8u6i.gif" alt=" " width="480" height="510"></a></p> <p>The full interactive walkthrough — with several failure cases — is here:<br> 👉 <a href="https://flowexplain.com/explainers/kubernetes-health-probes" rel="noopener noreferrer">https://flowexplain.com/explainers/kubernetes-health-probes</a></p> <p>(It is on my own non-commercial site — no signup, no ads.)</p> <h2> I'd like your feedback </h2> <p>Does this interactive format help you understand the topic better than a no gimmick? I am asking because if it works well, I want to make moreinteractive tutorials like this for Kubernetes.</p> <p>And if anything here is technically wrong, please tell me and I will fix it.</p> kubernetes devops tutorial beginners