Exercise

Exercise: Deployment

1. In the votingapp directory, replace each Pod specification with a Deployment specification with a single replica.
   Name these Deployment files deploy-XXX.yaml where XXX is the name of the microservice (voteui, vote, ...)

2. Deploy the application defined by these specifications

3. Access the vote and result interfaces via NodePort Services

4. Delete a Pod. What happens ?

5. Delete the application

Tip

1. The Deployment specifications are as follows:

   deploy-voteui.yamldeploy-vote.yamldeploy-redis.yamldeploy-worker.yamldeploy-db.yamldeploy-result.yamldeploy-resultui.yaml

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     labels:
       app: vote-ui
     name: vote-ui
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: vote-ui
     template:
       metadata:
         labels:
           app: vote-ui
       spec:
         containers:
           - image: voting/vote-ui:latest
             name: vote-ui
   

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     labels:
       app: vote
     name: vote
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: vote
     template:
       metadata:
         labels:
           app: vote
       spec:
         containers:
           - image: voting/vote:latest
             name: vote
   

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     labels:
       app: redis
     name: redis
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: redis
     template:
       metadata:
         labels:
           app: redis
       spec:
         containers:
           - image: redis:7.0.8-alpine3.17
             name: redis
   

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     labels:
       app: worker
     name: worker
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: worker
     template:
       metadata:
         labels:
           app: worker
       spec:
         containers:
           - image: voting/worker:latest
             name: worker
   

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     labels:
       app: db
     name: db
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: db
     template:
       metadata:
         labels:
           app: db
       spec:
         containers:
           - image: postgres:15.1-alpine3.17
             name: postgres
             env:
               - name: POSTGRES_PASSWORD
                 value: postgres
             ports:
               - containerPort: 5432
                 name: postgres
   

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     labels:
       app: result
     name: result
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: result
     template:
       metadata:
         labels:
           app: result
       spec:
         containers:
           - image: voting/result:latest
             name: result
   

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     labels:
       app: result-ui
     name: result-ui
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: result-ui
     template:
       metadata:
         labels:
           app: result-ui
       spec:
         containers:
           - image: voting/result-ui:latest
             name: result-ui
   

2. Deploy the application with the following command from the votingapp directory:

   kubectl apply -f .
   

3. As before, using the IP address of one of the cluster nodes, you can access the vote and result interfaces via ports 31000 and 31001 respectively.

   

   

4. Each Pod is now managed by a Deployment. If a Pod is deleted, another Pod is automatically created to replace it.

   List of Pods:

   $ kubectl get po
   NAME                         READY   STATUS    RESTARTS   AGE
   db-647c8f548b-j7z79          1/1     Running   0          3m35s
   redis-6f95f75d56-7gwjz       1/1     Running   0          3m35s
   result-7f897b4d58-qqtt4      1/1     Running   0          3m35s
   result-ui-5cdd74d999-q5tx7   1/1     Running   0          3m34s
   vote-6c847fd45-fpprh         1/1     Running   0          3m35s
   vote-ui-74849dd9b4-gwcq9     1/1     Running   0          3m35s
   worker-8655654586-k44vw      1/1     Running   0          3m35s
   

   Deleting a Pod (e.g., worker):

   $ kubectl delete po worker-8655654586-k44vw 
   pod "worker-8655654586-k44vw" deleted
   

   A new Pod is automatically launched to replace the one that was deleted.

   $ kubectl get po                                 
   NAME                         READY   STATUS    RESTARTS   AGE
   db-647c8f548b-j7z79          1/1     Running   0          5m15s
   redis-6f95f75d56-7gwjz       1/1     Running   0          5m15s
   result-7f897b4d58-qqtt4      1/1     Running   0          5m15s
   result-ui-5cdd74d999-q5tx7   1/1     Running   0          5m14s
   vote-6c847fd45-fpprh         1/1     Running   0          5m15s
   vote-ui-74849dd9b4-gwcq9     1/1     Running   0          5m15s
   worker-8655654586-mmzgh      1/1     Running   0          4s
   

   A Deployment ensures that Pods are always present. If we had deleted a Pod that was not managed by a Deployment (a Naked Pod), no new Pod would be automatically created to replace it.

5. We delete the application with the following command:

   kubectl delete -f vote.yaml