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Kubernetes ​

Components ​

Manifest ​

shell
$ kubectl create -f deploy.yaml # Create manifest file
yaml
apiVersion: v1
kind: Pod # Deployment, Service, …
metadata:
	name: redis
	labels:		
		app: todo
		component: redis
spec:
	containers:
	- name: redis
	  image: redis # docker image
	- ports:
		- containerPort: 6379
	- resources:
		- limits:
		- cpu: 100m
	- args:
		- redis-server
		- --requirepass ccp2
		- --appendonly yes

Pods ​

shell
$ kubectl get pods # List all pods
$ kubectl delete pod <name>
  • Set of 1 or more container
  • Containers share the same environment (tightly-coupled)
    • Memory
    • Storage volumes
    • Network (same IP. They use localhost to communicate between them)
  • Cattle strategy: if a container fail, whole pod is recreated from scratch
  • Labels: key-value tag assigned to pods to help services target them with queries

Services ​

shell
$ kubectl get svc # List all services
  • Regroup a set of pods into a single resource
  • Provide an endpoint to incoming pods
  • Load-balances the incoming request

Three types of load balancing

  • ClusterIP – Most common one. Can't be access from the outside of the cluster
  • NodePort – Can be access from outside with <node_ip>:<node_port>
  • LoadBalancer – Use the cloud provider load-balancer on top of NodePort

Deployments ​

Rolling update: push changes without interrupting the service by creating a new replica set

shell
$ kubectl get deployments # List running, updated and available replicas
$ kubectl rollout status <name>

Resources ​