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Kubernetes

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While we get started, go make sure you have a working GitHub account.

How did we get here?

  • Two weeks ago, we talked about containers in general and how they allow encapsulation of an application
  • Last week, we built some web apps
  • Tonight we'll look at how Kubernetes allows us to automate cloud application deployments

What is GitOps and CI/CD?

  • "Continuous integration" - code commits are automatically tested on every commit
  • "Continuous delivery" - code that passes tests is automatically installed on servers
  • GitOps - the entire state of an application is determined by one or more git repos, allowing automated upgrades and downgrades

Legally required intro for every Kubernetes talk

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  • Kubernetes was born in 2015 from the Borg project within Google
  • Abbreviated "k8s" - k, 8 random letters, s
  • Greek for "helmsman" - steering wheel logo
  • Seven-sided for "7 of 9", the friendly Borg
  • Google partnered with the Linux Foundation to form the Cloud Native Compute Foundation, to development and maintain the project

What is Kubernetes?

  • Think of it as the kernel of your cloud operating system
  • It's a database, a scheduling engine, and a loop that tries to keep everything in compliance with your specifications
  • Tons of plugins to manage the details of container lifecycle, disk storage, or network routing/firewalling
  • Together these form a kind of "distros", like Amazon EKS, Red Hat OpenShift, or VMware Tanzu.

What isn't Kubernetes?

  • git repository
  • Continuous integration testing system
  • Continuous deployment system
  • Some of these might run on your cluster
  • Some of these are made by the CNCF and integrate very well

What defines an application?

  • Source code and its CPU/memory requirements
  • Short and long-term storage
  • Network connections

What defines an app?

  • Deployments - defines a pod of containers, and the replication and scaling strategy
  • Services - creates a load-balancer inside a cluster to contact selected pods
  • Ingress - maps the outside world to a service

Deployments

  • DaemonSet - run exactly one copy of a pod on every host in the cluster
    • Example - monitoring and statistics agent
  • ReplicaSet - run one or more copies of a stateless application
    • Probably your typical web app
  • StatefulSet - run exactly one copy of a pod with persistent storage
    • Example - database server
    • Can also enforce ordered startup for things like primary/replica databases

Why Kubernetes?

  • Kubernetes manages a cluster of servers and a distributed key-value database (etcd)
  • It accepts requests to deploy containers
  • It tracks resource consumption, and intelligently places containers
  • It monitors container health, and restarts failed containers
  • It load balances requests across replicas of a container
  • It gradually upgrades containers when a new version is deployed

Demo time

  • Go to github.com/ripleymj/bird-flock
  • Fork & clone a copy for yourself
  • Go to Actions -> Build Bird App and hit Run Workflow
  • Inspect the workflow result

Argo - step 1

  • Go to argocd.jmunixusers.org and log in
  • Add a new app
  • Give it a name, all lower case
  • Make the project name your Argo username

Argo - step 2

Source

  • Set the repository URL to your GitHub repo fork (do not use ripleymj)
  • Make the path k8s/

Destination

  • For cluster URL, choose the ondigitalocean.com address
  • Use your Argo username as the namespace

Argo - step 3

  • Hit Create at the top to save your app
  • Argo will immediately recognize the app hasn't been deployed and is out of sync with git
  • Click on the app to open the deployment map before hitting Sync