Kubernetes Deployments

Create New Deployment

Create a new deployment with nginx docker image

In this example:
Deployment Name : nginx-app
Docker Image : nginx - Image will be downloaded from Docker Hub
Replica Count : 3


Scnerio-1 : Create Deployment using CLI

Run following command to create the new deployment
# kubectl create deployment nginx-app --image=nginx --replicas=3 deployment.apps/nginx-app created

Scnerio-2 : Create Deployment using YAML

Create a YAML file and define the deployment configuration
# vi nginx-deploy.yaml apiVersion: apps/v1 kind: Deployment metadata: name: nginx-app labels: app: nginx-app spec: replicas: 3 selector: matchLabels: app: nginx-app template: metadata: labels: app: nginx-app spec: containers: - name: nginx image: nginx ports: - containerPort: 80
Apply the configuration defined in YAML file
# kubectl apply -f nginx-deploy.yaml deployment.apps/nginx-deployment created

Check Deployment Status

Check the details of newly created deployment
# kubectl get deployment NAME READY UP-TO-DATE AVAILABLE AGE nginx-app 0/3 3 0 9s
Check detailed configuration of deployment

Setting to note here are:
Selector : app=nginx-app - This value is used find which pods are associated with this deployment.
Replicas : This show how many replicas are desired and what is the current status
StrategyType : RollingUpdate - This is default value and defines the container update strategy.


# kubectl describe deployment nginx-app Name: nginx-app Namespace: default CreationTimestamp: Fri, 29 Apr 2022 23:58:49 -0400 Labels: app=nginx-app Annotations: deployment.kubernetes.io/revision: 1 Selector: app=nginx-app Replicas: 3 desired | 3 updated | 3 total | 3 available | 0 unavailable StrategyType: RollingUpdate MinReadySeconds: 0 RollingUpdateStrategy: 25% max unavailable, 25% max surge Pod Template: Labels: app=nginx-app Containers: nginx: Image: nginx Port: Host Port: Environment: Mounts: Volumes: Conditions: Type Status Reason ---- ------ ------ Available True MinimumReplicasAvailable Progressing True NewReplicaSetAvailable OldReplicaSets: NewReplicaSet: nginx-app-7f6fdf9556 (3/3 replicas created) Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal ScalingReplicaSet 6m14s deployment-controller Scaled up replica set nginx-app-7f6fdf9556 to 3
Check the details of pods associated with deployment nginx-app
# kubectl get pods -l app=nginx-app NAME READY STATUS RESTARTS AGE nginx-app-7f6fdf9556-bp7pf 1/1 Running 0 3m20s nginx-app-7f6fdf9556-m8tf7 1/1 Running 0 3m20s nginx-app-7f6fdf9556-rmj4b 1/1 Running 0 3m20s

Scaling Replicas

Scale the replica count from 3 to 5 in the nginx-app deployment
# kubectl scale deployment nginx-app --replicas=5 deployment.apps/nginx-app scaled
Check the details of scaled deployment
# kubectl get deployment nginx-app NAME READY UP-TO-DATE AVAILABLE AGE nginx-app 5/5 5 5 15m
# kubectl get pods
Replica count is now changed from 3 to 5
NAME READY STATUS RESTARTS AGE nginx-app-7f6fdf9556-46nxx 1/1 Running 0 2m16s nginx-app-7f6fdf9556-bp7pf 1/1 Running 0 15m nginx-app-7f6fdf9556-m8tf7 1/1 Running 0 15m nginx-app-7f6fdf9556-nzmhd 1/1 Running 0 2m16s nginx-app-7f6fdf9556-rmj4b 1/1 Running 0 15m

Create Services

Create service for the nginx-app deployment

Service Type : Load Balancer
Exposing service : Port 8080 (LoadBalancer) to port 80 (nginx container)
No we can use LoadBalancer IP:8080 to connect to nginx containers

# kubectl expose deployment nginx-app --type=LoadBalancer --port=8080 --target-port=80 service/nginx-app exposed
Check the details of service
# kubectl get services nginx-app NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE nginx-app LoadBalancer 10.99.180.191 8080:32290/TCP 111s
# kubectl describe service nginx-app Name: nginx-app Namespace: default Labels: app=nginx-app Annotations: Selector: app=nginx-app Type: LoadBalancer IP Family Policy: SingleStack IP Families: IPv4 IP: 10.99.180.191 IPs: 10.99.180.191 Port: 8080/TCP TargetPort: 80/TCP NodePort: 32290/TCP Endpoints: 172.17.0.3:80,172.17.0.4:80,172.17.0.5:80 + 2 more... Session Affinity: None External Traffic Policy: Cluster Events:

Accessing NGINX Container Web Services

Note: When using minikube, kubernetes IPs are internal and not accessible from outside. But we can login to the kubernetes cluster server and access nginx web pages from there as a test.

Login to minikube cluster server
# minikube ssh
Access nginx webpage
# curl http://10.99.180.191:8080