DevOps Classroom Series – 10/Sept/2021

Resource Management

• Refer Here for the official docs
• Resource Requests: Minimum Resources
• Resource Limits: Capping Resource Usage
• Refer Here for the changeset containing k8s pod with resource limits

Labels

• Labels provide identifying metadata for objects.
• These are fundamental quantities of the k8s object that will be used in grouping viewing and operating
• Label is key value pair

app: nginx
appVersion: 1.2.1
qt.com/app-version: 1.2.1

• Lets create a pod

kubectl run nginx --image=nginx:1.21.1 --labels "ver=1,app=nginx"
kubectl run nginx2 --image=nginx:1.21.1 --labels "ver=2,app=nginx"

• Lets get the pods kubectl get pods --show-labels
• Label selectors

kubectl get pods --selector="app in (nginx, httpd)"
kubectl get pods --selector="ver in (nginx, httpd)"
kubectl get pods --selector="ver in (1,5)"
kubectl get pods --selector='app!=nginx'
kubectl get pods --selector="ver notin (1,5)"
kubectl get pods --selector='!env' # doesnt have label with key env
kubectl get pods --selector='env' # has a label env with any value

Replica Set

• Till now we have run individual container as Pods.
• More often we want multiple replicas of our application to be running
  • Redundancy: mean failure can be tolerated
  • Scale: More requests can be served by your application.
• In ReplicaSets, we can specify the desired state in terms of how many replicas we want and kubernetes will ensure that all the replicas are working
• Refer Here for the replica set sample and Refer Herefor the fix with selector