TALK.md

0. What does Kubernetes do?

• k8s docs.

1. K8s Components

k8s docs.

• Types of machines in a k8s cluster:
  • control plane node(s) (or just called control plane),
  • worker nodes (or just called nodes).
• control plane has
  • kube-apiserver: k8s API frontend,
  • etcd: key-value store for cluster data,
  • kube-scheduler: assigns resources to nodes based on current constraints,
  • kube-controller-manager: several control loops in one process,
  • cloud-controller-manager: several cloud-specific control loops in one process.
• worker nodes have
  • kubelet: manages containers deployed to that node,
  • kube-proxy: manages network rules on nodes,
  • Container Runtime: what runs the containers. Any implementation of the K8s Container Runtime Interface (e.g., CRI provided for Docker is the most common).

2. K8s API Objects

• Abstraction of Workload:
  • Pod: smallest deployable unit — holds one or more containers and runs it in a shared context
  • Workload resources: Used to manage groups of Pods
    • Deployment: for managing stateless Pods
      • ReplicaSet: abstraction to manage a number of identical Pods. Typically not used directly.
    • StatefulSet: for managing stateful Pods (e.g., DBs)
• Abstraction of Storage
  • Volume: many types of volumes provided by plugins (local, network/distributed FS, cloud)
• Abstraction of Networking
  • Service
  • Ingress
• Abstraction of Configuration
  • ConfigMaps
  • Secrets
  • Note on environment variables: The Twelve-Factor App - Config

3. K8s

Install minikube and kubectl

• https://kubernetes.io/docs/tasks/tools/

• https://minikube.sigs.k8s.io/docs/start/

• eval "$( kubectl completion bash )"

• eval "$( minikube completion bash )"

Minikube

• minikube start

• kubectl get nodes

• minikube status

• kubectl version

• minikube delete

Kubectl

• kubectl get nodes

• kubectl get pod

• kubectl get pod -o wide

• kubectl get services

• kubectl create deployment nginx-deploy --image=nginx

• kubectl get deployment

• kubectl get replicaset

• kubectl edit deployment nginx-deploy

• kubectl logs [pod]

• kubectl exec -it {pod} -- bin/bash

• kubectl delete deployment nginx-deploy

MongoDB deployment

• taken from https://gitlab.com/nanuchi/youtube-tutorial-series/-/tree/master/demo-kubernetes-components

  kubectl apply -f mongodb/mongo-secret.yaml
  kubectl apply -f mongodb/mongo.yaml
  kubectl apply -f mongodb/mongo-configmap.yaml 
  kubectl apply -f mongodb/mongo-express.yaml

  kubectl get pod
  kubectl get pod --watch
  kubectl get pod -o wide
  kubectl get service
  kubectl get secret
  kubectl get all | grep mongodb

  kubectl describe pod mongodb-deployment-xxxxxx
  kubectl describe service mongodb-service
  kubectl logs mongo-express-xxxxxx

  minikube service mongo-express-service

4. Patterns / Applications

• Package manager: https://helm.sh/
• Lightweight K8s: https://k3s.io/
• https://prometheus.io/docs/introduction/overview/
• Lens IDE https://k8slens.dev/

5. Alternatives

• Docker Swarm
• HashiCorp Nomad

Other resources

• Kubernetes Tutorial for Beginners (FULL COURSE in 4 Hours)
  • https://gitlab.com/nanuchi/youtube-tutorial-series/-/tree/master/
• Perlcon: Deploying Perl Apps using Docker, Gitlab & Kubernetes
• Salt Lake Perl Mongers - 11/8/16 - Scott Wiersdorf - "High Availability Perl with Kubernetes"
  • https://solitum.net/posts/high-availability-perl-with-kubernetes/
  • https://github.com/scottw/ha-perl-k8s
• NetworkChuck: You need to learn Kubernetes RIGHT NOW!!