Book Image

The Kubernetes Book

By : Nigel Poulton, Pushkar Joglekar
Book Image

The Kubernetes Book

By: Nigel Poulton, Pushkar Joglekar

Overview of this book

Kubernetes is the leading orchestrator of cloud-native apps. With knowledge of how to work with Kubernetes, you can easily deploy and manage applications on the cloud or in your on-premises data center. The book begins by introducing you to Kubernetes and showing you how to install it. You’ll learn how to use Kubernetes Services and bring stable and reliable networking to apps that are deployed on Kubernetes. You'll delve deep into the powerful storage subsystem of Kubernetes and learn how to leverage the variety of external storage backends in your applications. As the book progresses, it shows you how to use features such as DaemonSets, Helm, and RBAC to enhance your Kubernetes applications. You'll explore the six categories of identifying vulnerabilities and look at a few ways to prevent and mitigate them. You'll also look at ways to secure the software delivery pipeline by discussing some image-related best practices. The book ends by sharing with you some resources that’ll help take your Kubernetes knowledge to the next level. By the end of the book, you’ll have the confidence and skills to leverage all the features of Kubernetes to develop scalable applications.
Table of Contents (23 chapters)
Free Chapter
1
Chapter 1
3
Chapter 2
5
Chapter 3
7
Chapter 4
9
Chapter 5
11
Chapter 6
13
Chapter 7
15
Chapter 8
17
Chapter 9
19
Chapter 10
21
Chapter 11

Jobs and CronJobs

Jobs, that is, batch jobs, are stable resources in the batch/v1 API group. They are useful when you need to run a specific number of a particular Pod, and you need guarantees that they'll all successfully complete.

Here are a couple of subtleties worth noting:

  • Jobs don't have the concept of desired state.
  • Pods that are part of a job are short-lived.

These two concepts separate Jobs from other objects such as Deployments, DaemonSets, and StatefulSets. While those objects keep a specified number of a certain Pod running indefinitely, Jobs manage a specified number of a certain Pod and make sure they complete and exit successfully.

The Job object implements the usual controller and watch loop. If a Pod that the Job object spawns fails, the Job will create another in its place. Once all the Pods managed by a Job complete, the Job itself completes.

Use cases include typical batch-type workloads.

Interestingly, Jobs can be useful...