Skip to content

Latest commit

 

History

History
251 lines (211 loc) · 6.69 KB

kubernetes.md

File metadata and controls

251 lines (211 loc) · 6.69 KB
Raw

Kubernetes/K8s Architecture

  • Helps in Container Orchestration technology

k8s

Subscription

  • ID against which billing is done for Azure resources
  • Can have multiple resource groups

Resource Group

  • Logical way of consolidating things
  • Helps in setting permission & budget environment can be created based on restrictions(Eg. PROD RG can be 4CPU,16GB, while Non-PROD can be 2GB,8GB)

Service Connection

  • Azure Development Portal(dev.azure.com) & Azure Deployment Portal(portal.azure.com) can be connected using Service Connection(Eg. Azure Resource Manager)

Steps to connect

  • az login
  • Then login in Website portal which opens up
  • az aks get-credentials --resource-group <> --name <> --subscription <>
  • This creates kube-config in local system and links the same. And then run Docker Desktop before connecting to ACR
  • az acr login -n <>
  • If Connection Verification to be disabled : SET AZURE_CLI_DISABLE_CONNECTION_VERIFICATION=1

Alternative Ways to connect

  • az account set --subscription "<>"
  • az aks get-credentials --resource-group <> --name <>

Kubernetes Commands

  • Checking servies in specific namespace

kubectl get services -n <>

  • Entering inside POD

kubectl exec -it <> -n <> -- bash

  • Checking Logs

kubectl logs -f <>

  • Command to check descrypted base64 code

echo <> | base64 -d

  • Check secret values

kubectl edit secrets <> -n <>

  • Login to ACR

docker login <> -u <> -p <>

  • Manually build Docker image & Push in ACR & tag it

docker build -t demo-application:0.6 . docker tag demo-application:0.6 <<acr-name.io>>/demo-application:0.6 docker push <acr-name.io>>/demo-application:0.6

  • Get Object Names(pods/configmap/secrets/all/svc/services)

kubectl get <>

  • Describe any object

kubectl describe pod <>

  • Check last 1hr logs

kubectl logs --since=1h pod-id

  • Check Top PODs

kubectl top pods

  • Check Nodes

kubectl get nods

  • Delete deployment(Service is a logical name of deployment. Not required. But can be done explicitly)

kubectl delete deployment <> kubectl delete service <>

  • Check ACR Repository List

az acr repository list --subscription <> --name <>

  • Check Tags for specific repository

az acr repository show-tags --subscription <> --name <> --repository <>

Containers

Nodes

  • Worker machine where Containers launched by K8s

Cluster

  • Group of nodes
  • If one node fails, its accessible through other nodes

Kube Components

  • API Server
  • etcd : Key value store
  • kubelet
  • Container Runtime
  • Controller
  • Scheduler

POD

  • Container encapsulated as PODs and deployed in Node
  • A POD can have multi PODs. But its a good practice to have one

Replication Controllers

  • Old approach. Now obsolete
  • PODs encapsulated inside Replication Controllers for high availability
  • In below POD Definition, apiVersion(v1) & kind(Pod) is skipped, rest all appended in spec-template
apiVersion: v1
kind: ReplicationController
metadata:
  name: myapp-rc
  labels:
    app: myapp
    type: api-service
spec:
  template:
    <<POD Definition>>
    metadata:
      name: myapp-pod
      labels:
        app: myapp
        type: api-service
    spec:
      containers:
      - name: api-controller
        image: api-docker-image
replicaes: 4

ReplicaSet

  • Newer version of Replication Controller used now
  • ReplicaSet is defined in apps/v1 version
  • Selector-matchLabels is mandatory here as a Replicaset can take care of pre created different PODs also
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: myapp-rs
  labels:
    app: myapp
    type: api-service
spec:
  template:
    <<POD Definition>>
    metadata:
      name: myapp-pod
      labels:
        app: myapp
        type: api-service
    spec:
      containers:
      - name: api-controller
        image: api-docker-image
replicaes: 4
selector:
  matchLabels:
    type: api-service

Upscaling Replicas

  • kubectl replace -f replicaset-def.yaml
  • kubectl scale --replicas=6 -f replicaset-def.yaml
  • kubectl scale --replicas=6 replicaset my-replicaset

Deployment

  • Deployment object created in Node which encapsulates the ReplicaSet
  • Below creates a Deployment, ReplicaSet, Service objects
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-rs
  labels:
    app: myapp
    type: api-service
spec:
  template:
    <<POD Definition>>
    metadata:
      name: myapp-pod
      labels:
        app: myapp
        type: api-service
    spec:
      containers:
      - name: api-controller
        image: api-docker-image
replicaes: 4
selector:
  matchLabels:
    type: api-service

Deployment Rollouts

  • Deployment Strategies: Recreate & RollingUpdate(Default)
  • Update updates all PODs at once. Not a good approach
  • Rollout is better as one POD is updated at a time
  • It creates a new ReplicaSet where PODs are deployed either at once or one at a time based on strategy
  • Rollout & versioning can be seen with below command

kubectl rollout status deployment/myapp-deployment kubectl rollout history deployment/myapp-deployment kubectl rollout undo deployment/myapp-deployment

Networking

  • K8s expects Developer to set the Networks
  • All containers/PODs communicate to each other without NAT(Network Address Translation)
  • While all nodes can communicate with all Containers without NAT
  • PODs accessible within Nodes
  • Service Ports are 30000-32767
  • POD has Target Port say 80, While Service has Port(Say 80).And node has NodePort in range 30K
apiVersion: v1
kind: Service
metadata:
  name: myapp-service
spec:
  type: NodePort
  ports:
    - targetPort: 80
      port: 80
      nodePort: 32767
  <<POD Definition to link Service to POD>>
  selector:
    app: myapp
    type: front-end

Multi Services Networking

  • Can be done using Cluster IP of AKS
apiVersion: v1
kind: Service
metadata:
  name: back-end
spec:
  type: ClusterIP
  ports:
    - targetPort: 80
      port: 80
  <<POD Definition to link Service to POD>>
  selector:
    app: myapp
    type: front-end

References

  • Kubernetes for Absolute Beginners(Mumshad Mannambeth), KodeKloud Training