Completek8s Classroomnotes 03/Sep/2023

Kubernetes Networking contd…

Internet/External to Service Networking (contd)

• Routing traffic to Kubernetes (Ingress)
  • Layer 4: Load Balancer
  • Layer 7: Ingress Controller

Layer 4 Load Balancer

• When we create a k8s service, we can specify the type LoadBalancer. The implementation of Load Balancer is given by cloud controller which knows how to create a load balancer for your service

Kubernetes Service

Node Port

• This service provides a simple way for external software to route traffic to pods
• Nodeport service exposes a fixed port on all nodes, which routes to applicable pods.
• nodePort (.spec.ports[].nodePort) field specify the port to be opened all all nodes for the corresponding port on Pods
• While creating the service if we leave nodePort field empty k8s will automatically selects a unique port 30000-32767
• nginx deployment

```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  selector:
    matchLabels:
      app: nginx
  replicas: 2
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.14.2
        ports:
        - containerPort: 80

• Lets use nginx with nodePort

---
apiVersion: v1
kind: Service
metadata:
  name: nginx-svc
spec:
  type: NodePort
  selector:
    app: nginx
  ports:
    - name: nginx-svc
      protocol: TCP
      port: 80
      targetPort: 80
      nodePort: 30000

• We will try LoadBalancer and ExternalName in future sessions
• Note: K8s doesnot have an inbuilt layer 7 load balancer, so we need to understand ingress and ingress controller.