Kubernetes Jobs and CronJobs

Photo by Jordan Benton on Pexels

Most modern applications use a client-server architecture, where the client is a browser or mobile app, and the server is a long-running process. However, in some cases, you may want a program to be short-lived and terminate immediately after it has executed some tasks. In Unix, you can use shell commands to execute tasks and cron jobs to run such tasks periodically.

Kubernetes offers a workload type that is similar to Unix commands and cron jobs. If you have a task that needs to run until completion, a Kubernetes Job is the right workload type for you. Think of Jobs as a batch processor. If you need to run periodically, a Kubernetes Cron Job is the ideal workload type for you.

Jobs

A Kubernetes Job is a workload controller that represents a finite task. Jobs differ from other controller objects in that Jobs manage the task as it runs to completion, rather than managing an ongoing desired state (such as the total number of running Pods). When a specified number of pods reach completion, the Job is said to have successfully completed.

Kubernetes Jobs are useful for large computation and batch-oriented tasks. Jobs can be used to support parallel execution of Pods. You can use a Job to run independent but related work items in parallel: sending emails, rendering frames, transcoding files, scanning database keys, etc

To create Jobs with kubectl we can use kubectl create -f <jobfile.yaml> -n namespacename and to monitor job progress we can use kubectl get jobs -n namespacename. Similarly, we can use kubectl get events -n namespacename to look at the key events.

Running and monitoring a Job through Nirmata is easy. Simply Import the yaml or create a Job using intuitive UI.

Nirmata dashboard for monitoring jobs.

Job specifications and status on Nirmata dashboard

Cron Jobs:

Cron Jobs are a familiar tool for most developers and system administrators who have a need to run jobs based on a schedule. However, if you are using a Kubernetes cluster you might wonder how hard it is to schedule a cron job in order to handle time-based actions.

The Cron Job API became a standard feature in Kubernetes in 1.8 and is widely used by the Kubernetes ecosystem for automated backups, synchronization with remote services, system, and application maintenance (upgrades, updates, cleaning the cache) and more.

Sometimes your work isn’t transactional. Instead of waiting for a user to click a button and have systems light up we sometimes need to respond to a specific time and take actions from there.

A CronJob is basically a Kubernetes Job with time-based scheduling and some specific parameters to handle failure. Each Kubernetes Job creates 1 to n pod. Those pods run a program defined for the task and exit when the task is over.

To create Cron Jobs on Kubectl we can use kubectl create -f <cronjobfile.yaml> -n namespacename and to monitor job progress we can use kubectl get cronjobs -n namespacename. Similarly, we can use kubectl get events -n namespacename to look at the key events.

With Nirmata, creating and monitoring CronJobs has never been easier. One can simply import the YAML or create a CronJob with the interactive UI and can sit back and monitor.

Nirmata dashboard for specifying CronJob

Nirmata dashboard for monitoring CronJobs.

CronJob specifications and status on Nirmata dashboard

Summary:

Our mission at Nirmata is to make it easy for all enterprises to adopt Kubernetes and open-source innovation. Nirmata provides simple, yet powerful abstractions, to make it easy for developers and operators to learn and manage Kubernetes at scale and in production environments.

Jobs and Cron Jobs are essential features of Kubernetes, but without proper governance, they are often overlooked or misused. Nirmata helps IT platform and operations teams run jobs and cron jobs for various one time or recurring tasks with ease thus helping teams to focus on business critical development.

You can explore Nirmata for free at https://try.nirmata.io!