Book Image

Getting Started with Kubernetes - Third Edition

By : Jonathan Baier, Jesse White
Book Image

Getting Started with Kubernetes - Third Edition

By: Jonathan Baier, Jesse White

Overview of this book

Kubernetes has continued to grow and achieve broad adoption across various industries, helping you to orchestrate and automate container deployments on a massive scale. Based on the recent release of Kubernetes 1.12, Getting Started with Kubernetes gives you a complete understanding of how to install a Kubernetes cluster. The book focuses on core Kubernetes constructs, such as pods, services, replica sets, replication controllers, and labels. You will understand cluster-level networking in Kubernetes, and learn to set up external access to applications running in the cluster. As you make your way through the book, you'll understand how to manage deployments and perform updates with minimal downtime. In addition to this, you will explore operational aspects of Kubernetes , such as monitoring and logging, later moving on to advanced concepts such as container security and cluster federation. You'll get to grips with integrating your build pipeline and deployments within a Kubernetes cluster, and be able to understand and interact with open source projects. In the concluding chapters, you'll orchestrate updates behind the scenes, avoid downtime on your cluster, and deal with underlying cloud provider instability within your cluster. By the end of this book, you'll have a complete understanding of the Kubernetes platform and will start deploying applications on it.
Table of Contents (23 chapters)
Title Page
Dedication
Packt Upsell
Contributors
Preface
Index

DaemonSets


While ReplicationControllers and Deployments are great at making sure that a specific number of application instances are running, they do so in the context of the best fit. This means that the scheduler looks for nodes that meet resource requirements (available CPU, particular storage volumes, and so on) and tries to spread across the nodes and zones.

 

 

 

 

 

 

This works well for creating highly available and fault tolerant applications, but what about cases where we need an agent to run on every single node in the cluster? While the default spread does attempt to use different nodes, it does not guarantee that every node will have a replica and, indeed, will only fill a number of nodes equivalent to the quantity specified in the ReplicationController or Deployment specification.

To ease this burden, Kubernetes introduced DaemonSet, which simply defines a pod to run on every single node in the cluster or a defined subset of those nodes. This can be very useful for a number of production...