Day 9/40
Kubernetes Services Explained - ClusterIP vs NodePort vs Loadbalancer vs External
Video Link
@piyushsachdeva
Git Repository
My Git Repo
We're going to look at service in kubernetes and its types as below list:
- ClusterIP
- NodePort
- LoadBalancer
- External Name
The goal is to expose our front-end app to users, we use service and its benefits.
As you can see in the below diagram, we are using service anywhere which it makes sure there is at least one pod serving and listening on specific port in our cluster and it's accessible only to what we specified.
(Photo from the video)
1. Node Port
(Photo from the video)
These services are ideal for applications that need to be accessible from outside the cluster, such as web applications or APIs. With NodePort services, we can access our application using the node’s IP address and the port number assigned to the service.
When we create a NodePort service, Kubernetes assigns a port number from a predefined range of 30000-32767.(source)
There are 3 ports to define:
-
nodePort- for external users -
port- for internal clients -
targetPort- container port
(Photo from the video)
multi-pod scenario
(Photo from the video)
Implementing
root@localhost:~# kubectl get nodes
NAME STATUS ROLES AGE VERSION
lucky-luke-control-plane Ready control-plane 4d v1.30.0
lucky-luke-worker Ready <none> 4d v1.30.0
lucky-luke-worker2 Ready <none> 4d v1.30.0
apiVersion: v1
kind: Service
metadata:
name: nodeport-svc
labels:
env: demo
spec:
selector:
env: demo
type:
NodePort
ports:
- nodePort: 30001
port: 80
targetPort: 80
root@localhost:~# kubectl apply -f nodeport.yaml
service/nodeport-svc created
root@localhost:~# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 4d
nodeport-svc NodePort 10.96.37.68 <none> 80:30001/TCP 15s
root@localhost:~# kubectl get svc -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 4d <none>
nodeport-svc NodePort 10.96.37.68 <none> 80:30001/TCP 23s env=demo
Note because we are using the kind for creating our cluster, we need to do extra step to expose our port outside the kind.
Mapping ports to the host machine
It needs recreating the cluster because of:
"It's not said explicitly in the official docs, but I found some references that confirm: your thoughts are correct and changing extraPortMappings (as well as other cluster settings) is only possible with recreation of the kind cluster."
source
So our kind cluster would be:
# three node (two workers) cluster config
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
nodes:
- role: control-plane
extraPortMappings:
- containerPort: 30001
hostPort: 30001
- role: worker
- role: worker
- Delete the current cluster
root@localhost:~# kind delete cluster --name `kind get clusters`
Deleting cluster "lucky-luke" ...
Deleted nodes: ["lucky-luke-control-plane" "lucky-luke-worker2" "lucky-luke-worker"]
- Create the cluster again with new feature
root@localhost:~# kind create cluster --config kind-lucky-luke.yaml --name lucky-luke
Creating cluster "lucky-luke" ...
✓ Ensuring node image (kindest/node:v1.30.0) 🖼
✓ Preparing nodes 📦 📦 📦
✓ Writing configuration 📜
✓ Starting control-plane 🕹️
✓ Installing CNI 🔌
✓ Installing StorageClass 💾
✓ Joining worker nodes 🚜
Set kubectl context to "kind-lucky-luke"
You can now use your cluster with:
kubectl cluster-info --context kind-lucky-luke
Have a question, bug, or feature request? Let us know! https://kind.sigs.k8s.io/#community 🙂
Agian with our cluster:
root@localhost:~# kind get clusters
lucky-luke
root@localhost:~# kubectl get nodes
NAME STATUS ROLES AGE VERSION
lucky-luke-control-plane Ready control-plane 9m14s v1.30.0
lucky-luke-worker Ready <none> 8m47s v1.30.0
lucky-luke-worker2 Ready <none> 8m47s v1.30.0
- Create deployment (in day 8/40):
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-deploy
labels:
env: demo
spec:
template:
metadata:
name: nginx-pod
labels:
env: demo
type: frontend
spec:
containers:
- name: nginx-container
image: nginx
ports:
- containerPort: 80
replicas: 3
selector:
matchLabels:
env: demo
root@localhost:~# kubectl create -f day08-deploy.yaml
deployment.apps/nginx-deploy created
root@localhost:~# kubectl get all
NAME READY STATUS RESTARTS AGE
pod/nginx-deploy-6bfd44d944-dlfcf 1/1 Running 0 71s
pod/nginx-deploy-6bfd44d944-rgmjn 1/1 Running 0 71s
pod/nginx-deploy-6bfd44d944-tpvfz 1/1 Running 0 71s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 14m
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/nginx-deploy 3/3 3 3 71s
NAME DESIRED CURRENT READY AGE
replicaset.apps/nginx-deploy-6bfd44d944 3 3 3 71s
- Create
service:
root@localhost:~# kubectl apply -f nodeport.yaml
service/nodeport-svc created
root@localhost:~# kubectl get all
NAME READY STATUS RESTARTS AGE
pod/nginx-deploy-6bfd44d944-dlfcf 1/1 Running 0 2m33s
pod/nginx-deploy-6bfd44d944-rgmjn 1/1 Running 0 2m33s
pod/nginx-deploy-6bfd44d944-tpvfz 1/1 Running 0 2m33s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 15m
service/nodeport-svc NodePort 10.96.145.18 <none> 80:30001/TCP 7s
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/nginx-deploy 3/3 3 3 2m33s
NAME DESIRED CURRENT READY AGE
replicaset.apps/nginx-deploy-6bfd44d944 3 3 3 2m33s
- Check the service:
root@localhost:~# kubectl describe svc nodeport-svc
Name: nodeport-svc
Namespace: default
Labels: env=demo
Annotations: <none>
Selector: env=demo
Type: NodePort
IP Family Policy: SingleStack
IP Families: IPv4
IP: 10.96.145.18
IPs: 10.96.145.18
Port: <unset> 80/TCP
TargetPort: 80/TCP
NodePort: <unset> 30001/TCP
Endpoints: 10.244.1.4:80,10.244.2.3:80,10.244.2.4:80
Session Affinity: None
External Traffic Policy: Cluster
Events: <none>
- Current state:
root@localhost:~# kubectl get pod,deploy,svc --show-labels -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES LABELS
pod/nginx-deploy-c95b4f658-gj6jl 1/1 Running 0 47s 10.244.2.4 lucky-luke-worker2 <none> <none> env=demo,pod-template-hash=c95b4f658,type=frontend
pod/nginx-deploy-c95b4f658-nc2qg 1/1 Running 0 47s 10.244.1.4 lucky-luke-worker <none> <none> env=demo,pod-template-hash=c95b4f658,type=frontend
pod/nginx-deploy-c95b4f658-nfgrn 1/1 Running 0 47s 10.244.2.3 lucky-luke-worker2 <none> <none> env=demo,pod-template-hash=c95b4f658,type=frontend
NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR LABELS
deployment.apps/nginx-deploy 3/3 3 3 47s nginx-container nginx env=demo env=demo
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR LABELS
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 21m <none> component=apiserver,provider=kubernetes
service/nodeport-svc NodePort 10.96.145.18 <none> 80:30001/TCP 6m5s env=demo env=demo
- Check the
servicefrom our local:
root@localhost:~# curl localhost:30001
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
2. Cluster IP
Because every pod which is restarted has got another IP address, we need to create a clusterIP service type. It's default service type in Kubernetes. We only need port and targetPort in its yaml configuration file.
selector section is related to deployment label.
(Photo from the video)
Implementation
apiVersion: v1
kind: Service
metadata:
name: clusterip-svc
labels:
env: demo
spec:
selector:
env: demo
type:
ClusterIP
ports:
- port: 80
targetPort: 80
root@localhost:~# kubectl apply -f clusterip.yaml
service/clusterip-svc created
root@localhost:~# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
clusterip-svc ClusterIP 10.96.242.10 <none> 80/TCP 6s
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 67m
nodeport-svc NodePort 10.96.145.18 <none> 80:30001/TCP 51m
root@localhost:~# kubectl get svc --show-labels -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR LABELS
clusterip-svc ClusterIP 10.96.242.10 <none> 80/TCP 23s env=demo env=demo
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 67m <none> component=apiserver,provider=kubernetes
nodeport-svc NodePort 10.96.145.18 <none> 80:30001/TCP 51m env=demo env=demo
root@localhost:~# kubectl describe svc clusterip-svc
Name: clusterip-svc
Namespace: default
Labels: env=demo
Annotations: <none>
Selector: env=demo
Type: ClusterIP
IP Family Policy: SingleStack
IP Families: IPv4
IP: 10.96.242.10
IPs: 10.96.242.10
Port: <unset> 80/TCP
TargetPort: 80/TCP
Endpoints: 10.244.1.4:80,10.244.2.3:80,10.244.2.4:80
Session Affinity: None
Events: <none>
root@localhost:~# kubectl get endpoints
NAME ENDPOINTS AGE
clusterip-svc 10.244.1.4:80,10.244.2.3:80,10.244.2.4:80 3m25s
kubernetes 172.19.0.2:6443 70m
nodeport-svc 10.244.1.4:80,10.244.2.3:80,10.244.2.4:80 54m
3. Load Balancer
LoadBalancer services are ideal for applications that need to handle high traffic volumes, such as web applications or APIs. With LoadBalancer services, we can access our application using a single IP address assigned to the load balancer.source
(Photo from the video)
Implementation
apiVersion: v1
kind: Service
metadata:
name: loadbalancer-svc
labels:
env: demo
spec:
selector:
env: demo
type: LoadBalancer
ports:
- port: 80
targetPort: 80
root@localhost:~# kubectl apply -f loadbalancer.yaml
service/loadbalancer-svc created
root@localhost:~# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
clusterip-svc ClusterIP 10.96.242.10 <none> 80/TCP 12m
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 80m
loadbalancer-svc LoadBalancer 10.96.153.185 <pending> 80:31076/TCP 7s
nodeport-svc NodePort 10.96.145.18 <none> 80:30001/TCP 64m
root@localhost:~# kubectl get all
NAME READY STATUS RESTARTS AGE
pod/nginx-deploy-c95b4f658-gj6jl 1/1 Running 0 59m
pod/nginx-deploy-c95b4f658-nc2qg 1/1 Running 0 59m
pod/nginx-deploy-c95b4f658-nfgrn 1/1 Running 0 59m
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/clusterip-svc ClusterIP 10.96.242.10 <none> 80/TCP 13m
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 80m
service/loadbalancer-svc LoadBalancer 10.96.153.185 <pending> 80:31076/TCP 15s
service/nodeport-svc NodePort 10.96.145.18 <none> 80:30001/TCP 64m
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/nginx-deploy 3/3 3 3 59m
NAME DESIRED CURRENT READY AGE
replicaset.apps/nginx-deploy-c95b4f658 3 3 3 59m
As we can see, EXTERNAL-IP for our LoadBalancer service type is <pending>. This is what we can provide an IP Address or DNS name for our users, and yer we don't have provision them in the service and it behaves as a NodePort service.
For more info
4. External Name
We actually map it to a DNS.
The below sample is from official documentation.source
apiVersion: v1
kind: Service
metadata:
name: my-service
namespace: prod
spec:
type: ExternalName
externalName: my.database.example.com
5. Creating service in command-line
Syntax:
kubectl create nodeport NAME [--tcp=port:targetPort] [--dry-run=server|client|none]
Example
kubectl create service nodeport myservice --node-port=31000 --tcp=3000:80
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