Kubernetes Patterns - Examples

This GitHub project contains the examples from Kubernetes Patterns - Reusable Elements for Designing Cloud-Native Applications book by Bilgin Ibryam and Roland Huß

Installation instructions for the example prerequisites are summarised in INSTALL. By default, you need access to a vanilla Kubernetes installation, like Minikube. If addons are required, the example description explains this additional requirement.

For feedback, issues or questions in general, please use the issue tracker to open issues. Also, we love contributions like spelling fixes, bug fixes, improvements, … Please open Pull Requests, we are happy to review them!

Patterns

All example are categorised according to the Book’s patterns category. Each of the examples is contained in an extra directory per pattern and is self-contained. ^[1]

Foundational Patterns

Predictable Demands: Our sample random generator dealing with hard requirements on ConfigMap and PersistentVolumeClaims as well as with resource limits.
Declarative Deployment: Rolling and fixed update of the random generator Deployment from version 1.0 to 2.0.
Health Probe: Liveness and Readiness probes for the random generator.
Managed Lifecycle: postStart and preStop hooks demonstrated with the random generator application.
Automated Placement: Example with node selector, pod and node affinity, taint and tolerations demonstrated.

Behavorial Patterns

Batch Job: Generate thousands of random numbers into a file with a batch job
Periodic Job: Reuses the Batch Job example, but runs it periodically at a configured schedule
Daemon Service: Sample maintenance script for maintenance jobs on every node of a cluster
Singleton Service: Example of a PodDisruptionBudget for controlling voluntary disruptions
Stateful Service: StatefulSet example for our random-generator
Service Discovery: Various ways how to access our random-generator REST service
Self Awareness: Using the Downward API for setting environment variables and mount resource fields as files with the random-generator service.

Structural Patterns

Init Container: Initialize a HTTP server’s HTML source from a remote git repository
Sidecar: Git polling example for a sidecar
Adapter: Adapter for exporting timing information from the sample random-generator application in a Prometheus format
Ambassador: Ambassador for moving on the log of the random-generator

Configuration Patterns

EnvVar Configuration: A simple example of how to use environment variables literally and from ConfigMaps and Secrets for our random-generator service.
Configuration Resource: Example how to configure the random-generator Spring Boot application with a ConfigMap
Immutable Configuration: Several examples of how to use immutable configuration containers for application configuration. This includes examples for the plain Docker case and for Kubernetes.
Configuration Template: Example how to use a template configuration standalone.xml which is processed with a template processed and filled with data from ConfigMap before a Wildfly server is started.

Advanced Patterns

Controller: Simple, pure shell based controller which watches ConfigMap resources for changes and restarts Pods by using a label selector provided as annotation. An additional example controller exposes an Ingress route when it detects an exposeService label attached to the service.
Operator: Operator based on the ConfigMap watch controller and introduces a CRD ConfigWatcher which connects a ConfigMap with a set of Pods to restart in case of a config change.
Elastic Scale: Horizontal and vertical scaling examples with the random-generator Service [*]
Image Builder: Setup a chained build on OpenShift and use Knative build for doing builds within the cluster.

This work is licensed under a Creative Commons Attribution 4.0 International License

1. Examples marked with an "*" are functional but still, lack the full instruction set for running the examples. If you feel adventurous, please try out the provided resource files yourself. Happy to take also PRs, did we already mention that we love contributions? ;)

neeravarora/examples