Sometime you must have heard about the application where multiple servers are running and an application is replicated on all servers to share the load of incoming requests. Its called load balancing by deploying multiple replicas of same application on all servers.
Now, how would you do this in Kubernetes?
In Kubernetes , you no need to even ask to server team to setup this kind of deployment setup and it is too easy to do it. You just need to add few lines in your Kubernetes configuration files.
So, how Kubernetes handling it?
in Kubernetes, you need create Deployment kind resources instead of Pod. In deployment configuration, you can declare how many replicas do you need to run your application and that is it. Now, Kubernetes will create number of pods you mentioned in replicas configuration and whenever you update your application code, deployment controller will handle to and will update all pods with updated application code automatically .
Here is very simple example to create the deployment in Kubernetes :
apiVersion: apps/v1
kind: Deployment
metadata:
name: my-deployment
labels:
app: my-deployment
spec:
replicas: 2
selector:
matchLabels:
app: my-deployment
template:
metadata:
labels:
app: my-deployment
spec:
containers:
- name: my-apache
image: phpstorm/php-73-apache-xdebug-27
ports:
- containerPort: 80
lifecycle:
postStart:
exec:
command: ["/bin/sh", "-c", "echo '<?php sleep(5);echo \"Server Id is \".$_SERVER[\"SERVER_ADDR\"]; ?>' > index.php"]
---
apiVersion: v1
kind: Service
metadata:
name: my-service-1
spec:
selector:
app: my-deployment
type: NodePort
ports:
- name: http
port: 80
targetPort: 80
nodePort: 30037
protocol: TCP
---
