Step-00: Pre-requisites¶

Verify if GKE Cluster is created

Verify if kubeconfig for kubectl is configured in your local terminal

# Configure kubeconfig for kubectl
gcloud container clusters get-credentials <CLUSTER-NAME> --region <REGION> --project <PROJECT>

# Replace Values CLUSTER-NAME, REGION, PROJECT
gcloud container clusters get-credentials standard-cluster-private-1 --region us-central1 --project kdaida123

# List Kubernetes Nodes
kubectl get nodes

Step-01: Introduction¶

Kubernetes Namespaces - LimitRange
Kubernetes Namespaces - Declarative using YAML

Step-02: Create Namespace manifest¶

Important Note: File name starts with 01- so that when creating k8s objects namespace will get created first so it don't throw an error.
```
apiVersion: v1
kind: Namespace
metadata:
  name: qa
```

Step-03: Create LimitRange manifest¶

Instead of specifying resources like cpu and memory in every container spec of a pod defintion, we can provide the default CPU & Memory for all containers in a namespace using LimitRange

apiVersion: v1
kind: LimitRange
metadata:
  name: default-cpu-mem-limit-range
  namespace: qa
spec:
  limits:
    - default:
        cpu: "400m"  # If not specified default limit is 1 vCPU per container     
        memory: "256Mi" # If not specified the Container's memory limit is set to 512Mi, which is the default memory limit for the namespace.
      defaultRequest:
        cpu: "200m" # If not specified default it will take from whatever specified in limits.default.cpu      
        memory: "128Mi" # If not specified default it will take from whatever specified in limits.default.memory
      max: 
        cpu: "500m"
        memory: "500Mi"
      min:       
        cpu: "100m"
        memory: "100Mi"
      type: Container

Step-04: Demo-01: Create Kubernetes Resources & Test¶

# Create Kubernetes Resources
kubectl apply -f 01-kube-manifests-LimitRange-defaults

# List Pods
kubectl get pods -n qa -w

# View Pod Specification (CPU & Memory)
kubectl describe pod <pod-name> -n qa
Observation: 
1. We will find the "Limits" in pod container equals to "defaults" from LimitRange
2. We will find the "Requests" in pod container equals to "defaultRequest"

# Sample from Pod description
    Limits:
      cpu:     400m
      memory:  256Mi
    Requests:
      cpu:        200m
      memory:     128Mi

# Get & Describe Limits
kubectl get limits -n qa
kubectl describe limits default-cpu-mem-limit-range -n qa

# List Services
kubectl get svc -n qa

# Access Application 
http://<SVC-External-IP>/

Step-05: Demo-01: Clean-Up¶

Delete all Kubernetes objects created as part of this section

# Delete All
kubectl delete -f 01-kube-manifests-LimitRange-defaults/

Step-06: Demo-02: Update Demo-02 Deployment Manifest with Requests & Limits¶

Negative case testing
When deployed with these Requests & Limits where cpu=600m in limits which is above the max cpu = 500m in LimitRange default-cpu-mem-limit-range it should not schedule the pods and throw error in ReplicaSet Events.

File Name: 03-kubernetes-deployment.yaml

# Update Demo-02 Deployment Manifest with Requests & Limits
          resources:
            requests:
              memory: "128Mi" 
              cpu: "450m" 
            limits:
              memory: "256Mi"
              cpu: "600m"

Step-07: Demo-02: Create Kubernetes Resources & Test¶

# Create Kubernetes Resources
kubectl apply -f 02-kube-manifests-LimitRange-MinMax

# List Pods
kubectl get pods -n qa
Observation:
1. No Pod should be scheduled

# List Deployments
kubectl get deploy -n qa
Observation: 0/2 ready which means no pods scheduled. Verify ReplicaSet Events

# List & Describe ReplicaSets
kubectl get rs -n qa
kubectl describe rs <ReplicaSet-Name> -n qa
Observation: Below error will be displayed
 Warning  FailedCreate  18s (x5 over 56s)  replicaset-controller  (combined from similar events): Error creating: pods "myapp1-deployment-5dd9f78fd8-k5th6" is forbidden: maximum cpu usage per Container is 500m, but limit is 600m

# Get & Describe Limits
kubectl get limits -n qa
kubectl describe limits default-cpu-mem-limit-range -n qa

# List Services
kubectl get svc -n qa

# Access Application 
http://<SVC-External-IP>/

Step-08: Demo-02: Update Deployment resources.limit=500m¶

File Name: 03-kubernetes-deployment.yaml

# Demo-02: Update Deployment resources.limit=500m
          resources:
            requests:
              memory: "128Mi" 
              cpu: "450m"
            limits:
              memory: "256Mi"
              cpu: "500m" # This is equal to Max value defined in LimitRange, Pods will be scheduled.

Step-09: Demo-02: Deploy the updated Deployment¶

# Deploy the Updated Deployment
kubectl apply -f 02-kube-manifests-LimitRange-MinMax/03-kubernetes-deployment.yaml

# List Pods
kubectl get pods -n qa
Observation:
1. Pods should be scheduled now.

Step-10: Demo-02: Clean-Up¶

# Delete Demo-02 Kubernetes Resources
kubectl delete -f 02-kube-manifests-LimitRange-MinMax

References:¶

https://kubernetes.io/docs/tasks/administer-cluster/namespaces-walkthrough/
https://kubernetes.io/docs/tasks/administer-cluster/manage-resources/cpu-default-namespace/
https://kubernetes.io/docs/tasks/administer-cluster/manage-resources/memory-default-namespace/