Kubernetes for Developers

Jeff French

DevOps and Cloud Migration Experts

@jeff_french

Principal Consultant

Kubernetes is a container orchestrator.

Other schedulers / orchestrators include:

Docker Swarm

Apache Mesos / DCOS

HashiCorp Nomad

a pod is a collection of containers and volumes

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp-container
    image: busybox
    command: ['sh', '-c', 'echo Hello Kubernetes! && sleep 3600']
    volumeMounts:
    - mountPath: /test-pd
      name: test-volume
  volumes:
  - name: test-volume
    hostPath:
      path: /data
      type: Directory

a deployment describes the desired state of a set of pods and manages updates to those pods

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.7.9
        ports:
        - containerPort: 80

a service routes traffic to a set of pods

<service-name>.<namespace>.cluster.local

kind: Service
apiVersion: v1
metadata:
  name: my-service
spec:
  selector:
    app: MyApp
  ports:
  - name: http
    protocol: TCP
    port: 80
    targetPort: 9376
  - name: https
    protocol: TCP
    port: 443
    targetPort: 9377

An ingress exposes a service to the outside world

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  annotations:
    kubernetes.io/ingress.class: nginx
    kubernetes.io/ingress.provider: nginx
    kubernetes.io/tls-acme: "true"
    nginx.ingress.kubernetes.io/proxy-body-size: 512m
    nginx.ingress.kubernetes.io/proxy-connect-timeout: "15"
    nginx.ingress.kubernetes.io/proxy-read-timeout: "600"
  name: gitlab-unicorn
  namespace: gitlab
spec:
  rules:
  - host: gitlab.moonswitch.io
    http:
      paths:
      - backend:
          serviceName: gitlab-unicorn
          servicePort: 8181
        path: /
  tls:
  - hosts:
    - gitlab.moonswitch.io
    secretName: gitlab-gitlab-tls 

Max Unavailable

Absolute number or percentage of pods that can be unavailable at once during a deployment

Max Surge

Absolute number or percentage of pods that can be created in excess of the desired number of pods for a deployment

Rolling Update Strategies

maxUnavailable = 3

Our deployment may drop as low as 7 pods that are still active and serving traffic

maxSurge = 3

Our deployment may spike as high as 13 pods that are active and serving traffic

Rolling Update Strategies

Given a deployment with replicas = 10

a job runs a set of pods until successful completion

apiVersion: batch/v1
kind: Job
metadata:
  name: pi
spec:
  template:
    spec:
      containers:
      - name: pi
        image: perl
        command: ["perl",  "-Mbignum=bpi", "-wle", "print bpi(2000)"]
      restartPolicy: Never
  backoffLimit: 4

a horizontal pod autoscaler scales out a deployment based observed CPU utilization or other metrics

kubectl autoscale deployment php-apache --cpu-percent=50 --min=1 --max=10

Q & A Time!

Thanks!

Jeff French

Principal Consultant

 

Moonswitch

moonswitch.com

 

@jeff_french

Kubernetes for Developers

By Jeff French

Kubernetes for Developers

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