Kubernetes Patterns, 2nd Edition

Chapter 8. Periodic Job

The Periodic Job pattern extends the Batch Job pattern by adding a time dimension and allowing the execution of a unit of work to be triggered by a temporal event.

Problem

In the world of distributed systems and microservices, there is a clear tendency toward real-time and event-driven application interactions using HTTP and lightweight messaging. However, regardless of the latest trends in software development, job scheduling has a long history, and it is still relevant. Periodic jobs are commonly used for automating system maintenance or administrative tasks. They are also relevant to business applications requiring specific tasks to be performed periodically. Typical examples here are business-to-business integration through file transfer, application integration through database polling, sending newsletter emails, and cleaning up and archiving old files.

The traditional way of handling periodic jobs for system maintenance purposes has been to use specialized scheduling software or cron. However, specialized software can be expensive for simple use cases, and cron jobs running on a single server are difficult to maintain and represent a single point of failure. That is why, very often, developers tend to implement solutions that can handle both the scheduling aspect and the business logic that needs to be performed. For example, in the Java world, libraries such as Quartz, Spring Batch, and custom implementations with the ScheduledThreadPoolExecutor ...