Architecture

Components

Master

Apiserver

Schedulder

Nodes

Kubelet

kube-proxy

Container Engine

Key/Value Store

Key Concepts

• Containers
• Pod
• Label
• Selector
• Replication Controllers
• Replica Sets
• Deployment
• Services
• Volumes

Advance Resources

• Namespaces
• ConfigMaps
• Secrets
• Batch Jobs
• PetSets
• DaemoncSet
• Ingress

Defining an application

RSVP Application

Deployments

MongoDB

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: rsvp-db
spec:
  replicas: 1
  template:
    metadata:
      labels:
        appdb: rsvpdb
    spec:
      containers:
      - name: rsvpd-db
        image: mongo:3.3
        env:
        - name: MONGODB_DATABASE
          value: rsvpdata
        ports:
        - containerPort: 27017

RSVP App

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: rsvp
spec:
  replicas: 2
  template:
    metadata:
      labels:
        app: rsvp
    spec:
      containers:
      - name: rsvp-app
        image: teamcloudyuga/rsvpapp
        env:
        - name: MONGODB_HOST
          value: mongodb
        ports:
        - containerPort: 5000

Services

MongoDB

apiVersion: v1
kind: Service
metadata:
  name: mongodb
  labels:
    app: rsvpdb
spec:
  ports:
  - port: 27017
    protocol: TCP
  selector:
    appdb: rsvpdb

RSVP App

apiVersion: v1
kind: Service
metadata:
  name: rsvp
  labels:
    app: rsvp
spec:
  type: NodePort 
  ports:
  - port: 80
    targetPort: 5000
    protocol: TCP
  selector:
    app: rsvp

High availablity of application

• Pods Replicas
• Multiple nodes
• Multiple master

Service discovery of applications

• Services get registred with a DNS, which each node can access.
• With default installation, kube-dns service get delpoyed which
  • registers new service's VIP
  • resolves name to VIP

Load Balancing an application

• Internal
  • kube-proxy
• External

Autoscaling an application

• Horizontal Pod Scaling
  • Based on CPU usage now which uses heapster to collect CPU utilization.
  • Custom matrics support is coming

Rolling upgrade and rollback of an application

• Using Deployments

Internally connecting to other application

• using serivce VIP

Networking option to connect applications with-in the cluster

• Flat Networking
• All containers talks to other containers without NAT

Accessing the application from external world

• LoadBalancer (requires Cloud Provider's support)
• NodePort
• External IP
• Igress

Managing storage for application

• Volumes are per pod. Even if container in a pod goes down, volume exists.
• To use a volume, a pod specifies what volumes to provide for the pod (the spec.volumes field) and where to mount those into containers(the spec.containers.volumeMounts field).

Supported Volumes

• emptyDir
• hostPath
• gcePersistentDisk
• awsElasticBlockStore
• nfs
• iscsi
• flocker
• glusterfs
• rbd
• cephfs
• gitRepo
• secret
• persistentVolumeClaim
• downwardAPI
• azureFileVolume
• vsphereVolume

Demo

Download kubectl

$ curl -O  https://storage.googleapis.com/kubernetes-release/release/v1.3.5/bin/linux/amd64/kubectl
$ chmod +x kubectl
$ mv kubectl /usr/local/bin/kubectl

Configure kubectl

• Copy the share config file inside ~/.kube

  $ mkdie ~/.kube
  $ cp <PATH>/config ~/.kube
  

Create the namespace

$ kubectl create namespace <username>

Get the current context

$ export CONTEXT=`kubectl config view | awk '/current-context/ {print $2}'`

Update the default namespace for the current context

$ kubectl config set-context $CONTEXT --namespace=<username>

Create a deployment

$ kubectl run my-nginx --image=nginx --replicas=2 --port=80

List the pods and deployments

$ kubectl get pods
$ kubectl get deployments

Create a service and expose it using NodePort

$ kubectl expose deployment my-nginx --port=80 --type=NodePort

List the service

$ kubectl get services

Acccess the sevice using NodePort

Delete service and deloyment

$ kubectl delete svc my-nginx  
$ kubectl delete deployment my-nginx

Deploying RSVP app

Clone the repo

$ git clone https://github.com/cloudyuga/container-orchestration.git
$ cd container-orchestration/k8s

Create db

$ kubectl create -f rsvp-db.yaml
$ kubectl create -f rsvp-db-service.yaml

Create web frontend

$ kubectl create -f rsvp-web.yaml
$ kubectl create -f rsvp-web-service.yaml

List

$ kubectl get deployments
$ kubectl get svc

Scale

$ kubectl scale --replicas=4 deployments/rsvp

Delete

$ kubectl delete deployments/rsvp deployments/rsvp-db
$ kubectl delete svc/mongodb svc/rsvp