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Kubernetes for Developers

You're reading from   Kubernetes for Developers Use Kubernetes to develop, test, and deploy your applications with the help of containers

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Product type Paperback
Published in Apr 2018
Publisher Packt
ISBN-13 9781788834759
Length 374 pages
Edition 1st Edition
Languages
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Author (1):
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Joseph Heck Joseph Heck
Author Profile Icon Joseph Heck
Joseph Heck
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Table of Contents (12) Chapters Close

Preface 1. Setting Up Kubernetes for Development FREE CHAPTER 2. Packaging Your Code to Run in Kubernetes 3. Interacting with Your Code in Kubernetes 4. Declarative Infrastructure 5. Pod and Container Lifecycles 6. Background Processing in Kubernetes 7. Monitoring and Metrics 8. Logging and Tracing 9. Integration Testing 10. Troubleshooting Common Problems and Next Steps 11. Other Books You May Enjoy

Kubernetes concepts – selectors


Selectors are used in Kubernetes to connect resources together based on the labels they have (or don’t have). A selector is meant to provide a means to retrieve a set of resources in Kubernetes.

Most of the kubectl commands support a -l option that allows you to provide a selector to filter what it finds.

A Selector can be equality-based to represent specific values, or set-based to allow filtering and selection based on multiple values. Equality selectors use = or !=. Set selectors use in, notin, and exists. You can combine these in a selector to create more complex filters and selection criteria by appending the selectors together with a , between them.

For example, you might use a label app to represent a grouping of Pods that provide service to a specific application - in this case using the value flask and tier to represent the values of front-end, cache, and back-end tiers. A selector that would return all resources related to the app might be:

app=flask...
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