Kubernetes Service Types: ClusterIP and NodePort

1. Introduction

Kubernetes services provide stable IP addresses and DNS names to pods and can also load balance traffic between them. This lesson focuses on two common service types: ClusterIP and NodePort.

2. Service Types

In Kubernetes, services are defined by their type, which determines how they can be accessed:

• ClusterIP: Exposes the service on a cluster-internal IP.
• NodePort: Exposes the service on each Node’s IP at a static port.

3. ClusterIP

The ClusterIP service type is the default service type in Kubernetes. It makes the service accessible only within the cluster.

3.1 Key Features

• Internal Access Only: Accessible only from within the cluster.
• Load Balancing: Distributes traffic to all pods behind the service.

3.2 Example

Here’s how to create a ClusterIP service:

apiVersion: v1
kind: Service
metadata:
  name: my-clusterip-service
spec:
  type: ClusterIP
  selector:
    app: myapp
  ports:
    - port: 80
      targetPort: 8080

4. NodePort

The NodePort service type exposes the service on a static port on each node’s IP. This makes it accessible externally.

4.1 Key Features

• External Access: Can be accessed from outside the cluster.
• Static Port: Uses a static port for incoming traffic.

4.2 Example

Here’s how to create a NodePort service:

apiVersion: v1
kind: Service
metadata:
  name: my-nodeport-service
spec:
  type: NodePort
  selector:
    app: myapp
  ports:
    - port: 80
      targetPort: 8080
      nodePort: 30007

5. Best Practices

When using ClusterIP and NodePort services, consider the following best practices:

• Use ClusterIP for internal services to enhance security.
• Choose NodePort for services that need external access, but consider using LoadBalancer for more complex setups.
• Document port numbers and service types to avoid conflicts.

6. FAQ