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Chris Short Red Hat DevOpsDays Columbus Kubernetes Cron Jobs: Dreams Really Do Come True

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@ChrisShort devopsish.com 99999 Crons on the Wall 31 different daily newspapers Hundreds of cron jobs to run One RHEL 3 server running them The top of the hour was a nightmare sometimes No idea what broke when a cron failed

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@ChrisShort devopsish.com

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@ChrisShort devopsish.com Kubernetes Kubernetes is an open-source system for automating deployment, scaling, and management of containerized applications. https://kubernetes.io

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Pods Pods are the smallest deployable units of computing that can be created and managed in Kubernetes. A Pod is a group of one or more containers (such as Docker containers) with shared storage/network and a specification for how to run the containers. https://kubernetes.io/docs/concepts/workloads/pods/pod/ @ChrisShort devopsish.com

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Jobs "A job creates one or more pods and ensures that a specified number of them successfully terminate. As pods successfully complete, the job tracks the successful completions. When a specified number of successful completions is reached, the job itself is complete." https://kubernetes.io/docs/concepts/workloads/controllers /jobs-run-to-completion/ @ChrisShort devopsish.com

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CronJob A Cron Job creates Jobs on a time-based schedule. One CronJob object is like one line of a crontab (cron table) file. It runs a job periodically on a given schedule, written in Cron format. https://kubernetes.io/docs/concepts/workloads/controllers /cron-jobs/ @ChrisShort devopsish.com

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@ChrisShort devopsish.com

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Use Case My newsletter, DevOps’ish, is a static site generated with Hugo and run on Netlify I can write the newsletter set to a date in the future Hugo won't build page until date Netlify provides a build hook that will trigger builds when called. Calling the build hook URL via curl is a way to implement scheduled posts with Hugo on Netlify. @ChrisShort devopsish.com

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Let's Build a Kubernetes CronJob @ChrisShort devopsish.com (with a private registry because I'm a masochist)

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@ChrisShort devopsish.com

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@ChrisShort devopsish.com

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@ChrisShort devopsish.com

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@ChrisShort devopsish.com

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@ChrisShort devopsish.com

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@ChrisShort devopsish.com

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@ChrisShort devopsish.com

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Conclusion Built a Docker container Pushed the image to a private registry Configured Kubernetes to use the private registry Created secret to store the build hook URL Created the CronJob

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References Everything but the secret The Children's Illustrated Guide to Kubernetes What is a Job? | Kubernetes CronJob | Kubernetes Secret | Kubernetes Kubernetes: Cron Jobs chrisshort/k8s-cron-job-demo Google Cloud Registry (GCR) with external Kubernetes

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@ChrisShort devopsish.com