Kubernetes Patterns, 2nd Edition

Chapter 7. Batch Job

The Batch Job pattern is suited for managing isolated atomic units of work. It is based on the Job resource, which runs short-lived Pods reliably until completion on a distributed environment.

Problem

The main primitive in Kubernetes for managing and running containers is the Pod. There are different ways of creating Pods with varying characteristics:

Bare Pod

It is possible to create a Pod manually to run containers. However, when the node such a Pod is running on fails, the Pod is not restarted. Running Pods this way is discouraged except for development or testing purposes. This mechanism is also known as unmanaged or naked Pods.

ReplicaSet

This controller is used for creating and managing the lifecycle of Pods expected to run continuously (e.g., to run a web server container). It maintains a stable set of replica Pods running at any given time and guarantees the availability of a specified number of identical Pods. ReplicaSets are described in detail in Chapter 11, “Stateless Service”.

DaemonSet

This controller runs a single Pod on every node and is used for managing platform capabilities such as monitoring, log aggregation, storage containers, and others. See Chapter 9, “Daemon Service”, for a more detailed discussion.

A common aspect of these Pods is that they represent long-running processes that are not meant to stop after a certain time. However, in some cases there is a need to perform a predefined finite unit of work reliably and then shut ...