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LoadBalancer

Learn the LoadBalancer service type.

LoadBalancer

The LoadBalancer type requests a real external load balancer from the cloud provider (AWS, GCP, Azure) and gives it a public IP. It's built on top of NodePort: the load balancer spreads traffic to the node ports.

$ kubectl get svc web
NAME   TYPE           CLUSTER-IP    EXTERNAL-IP     PORT(S)        AGE
web    LoadBalancer   10.96.45.12   34.118.22.104   80:31512/TCP   2m

Each LoadBalancer service means a separate load balancer (and cost); for several HTTP services, Ingress, a single entry point, is preferred.

LoadBalancer locally

In Minikube, while minikube tunnel runs in a separate terminal, LoadBalancer services get a local IP. On bare-metal servers, tools like MetalLB take on this job:

# terminal 1
minikube tunnel
# terminal 2
$ kubectl get svc web
NAME   TYPE           EXTERNAL-IP     PORT(S)
web    LoadBalancer   10.96.45.12     80:31512/TCP
$ curl http://10.96.45.12

Practice A LoadBalancer service

Write a Service YAML: name web, type: LoadBalancer; selector app: web; port port: 80, targetPort: 8080.

Starter code

terminal
# buraya yaz

Sample solution

terminal
apiVersion: v1
kind: Service
metadata:
  name: web
spec:
  type: LoadBalancer
  selector:
    app: web
  ports:
    - port: 80
      targetPort: 8080

Expected output

service/web created
NAME   TYPE           CLUSTER-IP    EXTERNAL-IP     PORT(S)        AGE
web    LoadBalancer   10.96.45.12   34.118.22.104   80:31512/TCP   40s

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Why does a LoadBalancer service's EXTERNAL-IP stay <pending> in Minikube?

  • The pod isn't ready
  • There's a port conflict
  • There's no cloud provider to provide the load balancer Correct answer
  • The YAML is wrong

Explanation: The minikube tunnel command assigns a local external IP.

2 Make the service type a cloud load balancer.

Question 
spec:
  type: ____
Answer 
spec:
  type: LoadBalancer

Explanation: LoadBalancer requests an external IP.

3 Match.

Term Meaning
LoadBalancer Cloud load balancer
EXTERNAL-IP Public address
minikube tunnel Local external IP
MetalLB Bare-metal solution

All lessons in Intermediate

1 What is Kubernetes?

  1. What is Kubernetes?
  2. Why Kubernetes?
  3. Cluster architecture
  4. Control plane
  5. Worker node
  6. Summary - What is Kubernetes

2 Minikube

  1. What is Minikube?
  2. Installing Minikube
  3. minikube start
  4. minikube status
  5. minikube dashboard
  6. Summary - Minikube

3 kubectl basics

  1. What is kubectl?
  2. kubectl get
  3. kubectl describe
  4. kubectl apply
  5. kubectl delete
  6. Summary - kubectl

4 Pod

  1. What is a Pod?
  2. Pod YAML
  3. Creating a Pod
  4. Pod status
  5. Multi-container Pod
  6. Summary - Pod

5 Deployment

  1. What is a Deployment?
  2. Deployment YAML
  3. Replica count
  4. Rolling update
  5. Rollback
  6. Summary - Deployment

6 ReplicaSet

  1. What is a ReplicaSet?
  2. ReplicaSet YAML
  3. ReplicaSet selector
  4. Scaling
  5. Self-healing
  6. Summary - ReplicaSet

7 Service

  1. What is a Service?
  2. ClusterIP
  3. NodePort
  4. LoadBalancer
  5. Service selector
  6. Summary - Service

8 ConfigMap

  1. What is a ConfigMap?
  2. ConfigMap YAML
  3. Environment variable
  4. Mounting as a volume
  5. kubectl create configmap
  6. Summary - ConfigMap

9 Secret

  1. What is a Secret?
  2. Secret types
  3. Secret YAML
  4. Mounting a Secret
  5. kubectl create secret
  6. Summary - Secret

10 Namespace

  1. What is a Namespace?
  2. kubectl get namespaces
  3. Creating a Namespace
  4. The -n flag
  5. Default Namespace
  6. Summary - Namespace

11 Labels and selectors

  1. What is a label?
  2. Adding labels
  3. Label selector
  4. kubectl get -l
  5. Equality and set selectors
  6. Summary - Labels

12 Project: Multi-tier app

  1. Project design
  2. Database Deployment
  3. Web Deployment
  4. ConfigMap and Secret
  5. Putting it together - multi-tier

13 Troubleshooting

  1. kubectl logs
  2. kubectl exec
  3. kubectl describe pod
  4. CrashLoopBackOff
  5. Pending Pod
  6. Summary - Troubleshooting

14 Intermediate final

  1. Challenge - Pod YAML
  2. Challenge - Deployment
  3. Challenge - Service
  4. Challenge - ConfigMap
  5. Challenge - Intermediate project