Hands-On Intro To Kubernetes (And OpenShift)

Find the workshop notes at https://hackmd.io/N8gB_z0SREGDQ5c8DUb7og?both#Further-Reading

Intro to Kubernetes

Prerequisites

Docker https://www.docker.com/ (or Podman https://podman.io/)
Minikube https://minikube.sigs.k8s.io/docs/start/
Kubectl https://kubernetes.io/docs/tasks/tools/

Nodes

Kubernetes runs your workload by placing containers into Pods to run on Nodes. A node may be a virtual or physical machine, depending on the cluster. Each node contains the services necessary to run Pods, managed by the control plane.

Typically you have several nodes in a cluster; in a learning or resource-limited environment, you might have just one.

kubectl get nodes

Pods

Pods are the smallest deployable units of computing that you can create and manage in Kubernetes.

A Pod (as in a pod of whales or pea pod) is a group of one or more containers, with shared storage/network resources, and a specification for how to run the containers. A Pod's contents are always co-located and co-scheduled, and run in a shared context. A Pod models an application-specific "logical host": it contains one or more application containers which are relatively tightly coupled. In non-cloud contexts, applications executed on the same physical or virtual machine are analogous to cloud applications executed on the same logical host.

Create new pod (1-pod.yaml)
kubectl apply -f ./k8s/1-pod.yaml
kubectl get all
kubectl describe pod/hello
kubectl logs hello
kubectl get pods - See restarts
kubectl delete pod hello
kubectl apply -f ./k8s/2-webserver.yaml
kubectl get all
kubectl exec -it pod/webserver -- /bin/bash
- service nginx status
- exit
kubectl apply -f ./k8s/3-toolbox.json
kubectl exec -it pod/toolbox -- /bin/bash
printenv
curl google.com
curl webserver Log back into web server hostname -I log back in toolbox curl ip

Deployments

Pods by themselves are useless... introducing deployments.

A Deployment provides declarative updates for Pods ReplicaSets.

You describe a desired state in a Deployment, and the Deployment Controller changes the actual state to the desired state at a controlled rate. You can define Deployments to create new ReplicaSets, or to remove existing Deployments and adopt all their resources with new Deployments.

kubectl apply -f ./4-deployment.yaml
kubectl get all
kubectl logs hello-769fc65b75-8r85k
kubectl logs -f hello-769fc65b75-8r85k
kubectl scale deployment/hello --replicas=3
kubectl get all
kubectl get pods
kubectl get pods -l job=say-hello
kubectl logs hello-769fc65b75-mxn25
kubectl delete pod hello-769fc65b75-mxn25
kubectl get pods -l job=say-hello

Real application

kubectl apply -f ./k8s/5-front.yaml
kubectl get all
kubectl get all -l app=handsonk8s

How to reach? Services!

Services

An abstract way to expose an application running on a set of Pods as a network service.

With Kubernetes you don't need to modify your application to use an unfamiliar service discovery mechanism. Kubernetes gives Pods their own IP addresses and a single DNS name for a set of Pods, and can load-balance across them.

kubectl apply -f ./k8s/6-service.yaml
kubectl exec -it pod/toolbox -- /bin/bash
- curl localhost
- curl front
(other tab)
kubectl logs -f -l section=front --prefix=true
- curl front
- exit

Ingresses

An API object that manages external access to the services in a cluster, typically HTTP.

Ingress may provide load balancing, SSL termination and name-based virtual hosting.

kubectl apply -f ./k8s/7-ingress.yaml
curl $(minikube ip)

If using the IBM Cloud: https://cloud.ibm.com/docs/containers?topic=containers-ingress-about

API

Deploy the API

kubectl apply -f ./k8s/8-backend.yaml

Test in browser

kubectl apply -f ./k8s/9-adv-ingress.yaml
curl $(minikube ip)/api

Add environment variables

kubectl apply -f ./k8s/10-env.yaml

Add other API

Add other API service

name: handsonk8s-crash env var: CRASHING_API_URL

joellord / handson-k8s