Simplifying Namespaces and Resource Quotas in Kubernetes

 Kubernetes (K8s) excels in orchestrating containerized applications, but as projects scale, maintaining control becomes critical. This is where Namespaces and Resource Quotas step in. Let’s explore these concepts with a simple example.

Namespaces

Act as virtual clusters within a physical Kubernetes cluster. They provide logical separation, allowing you to divide resources and isolate workloads. This is particularly useful when multiple teams or projects share a single Kubernetes cluster. Each team can have their own namespace, preventing conflicts and ensuring resource isolation.

Example: Creating a Namespace

apiVersion: v1
kind: Namespace
metadata:
  name: my-namespace

Apply using :

$ kubectl apply -f namespace.yml
namespace/my-namespace created

$ kubectl get ns 
NAME              STATUS   AGE
default           Active   15d
istio-system      Active   10d
kube-node-lease   Active   15d
kube-public       Active   15d
kube-system       Active   15d
my-namespace      Active   37s
sts-app           Active   10d

Resource quotas

Enable you to control the resource consumption within a namespace. By defining limits on resources like CPU, memory, and pods, you can prevent a single namespace from monopolizing resources and ensure fair allocation among all namespaces. https://kubernetes.io/docs/concepts/policy/resource-quotas/

Example: Applying a Resource Quota

apiVersion: v1
kind: ResourceQuota
metadata:
  name: my-resource-quota
  namespace: my-namespace
spec:
  hard:
    pods: "10"
    requests.cpu: "4"
    requests.memory: 2Gi
    limits.cpu: "6"
    limits.memory: 4Gi

Apply using :

# applying resource quotas
$ kubectl apply -f resource-quotas.yml
resourcequota/my-resource-quota created

# accessing resource quotas in specified name space .
$ kubectl get quota -n my-namespace
NAME                AGE   REQUEST                                                 LIMIT
my-resource-quota   93s   pods: 0/10, requests.cpu: 0/4, requests.memory: 0/2Gi   limits.cpu: 0/6, limits.memory: 0/4Gi

Deploy some stateful applications within these quota limits.

apiVersion: apps/v1
kind: Deployment 
metadata:
  name: nginx-app
  namespace: my-namespace
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx-app
  template:
    
    metadata:
      name:  nginx-app
      labels: 
        app: nginx-app
    spec:
      containers:
      - image:  gudditi/sample-web-app
        name:  nginx-app
        ports:
        - containerPort: 80
        resources:
          requests:
            cpu: "1"
            memory: "100Mi"
          limits:
            cpu: "2"
            memory: "300Mi"  

---

apiVersion: v1
kind: Service 
metadata:
  name: nginx-svc
  namespace: my-namespace
spec:
  type: NodePort
  selector:
    app: nginx-app
  ports:
  - name: http
    port:  80
    targetPort: 80

apply it :

$ kubectl apply -f deployment.yml
deployment.apps/nginx-app unchanged
service/nginx-svc unchanged

guddi@Gudditi MINGW64 ~/OneDrive/Desktop/test (main)
$ kubectl get all -n my-namespace
NAME                            READY   STATUS    RESTARTS   AGE
pod/nginx-app-cf7886869-5ngk7   1/1     Running   0          7m7s
pod/nginx-app-cf7886869-j9cpj   1/1     Running   0          7m7s
pod/nginx-app-cf7886869-m2hkz   1/1     Running   0          7m7s

NAME                TYPE       CLUSTER-IP     EXTERNAL-IP   PORT(S)        AGE
service/nginx-svc   NodePort   10.98.233.51   <none>        80:31246/TCP   7m7s

NAME                        READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/nginx-app   3/3     3            3           7m7s

NAME                                  DESIRED   CURRENT   READY   AGE
replicaset.apps/nginx-app-cf7886869   3         3         3       7m7s

Let’s Check Quota:

$ kubectl describe quota my-resource-quota -n my-namespace
Name:            my-resource-quota
Namespace:       my-namespace
Resource         Used   Hard
--------         ----   ----
limits.cpu       6      6
limits.memory    900Mi  4Gi
pods             3      10
requests.cpu     3      4
requests.memory  300Mi  2Gi

In summary, Namespaces provide logical isolation, while ResourceQuotas offer control over resource usage within those namespaces. Together, they are powerful tools for managing and organizing workloads in a Kubernetes cluster.