[Cloud] 5. Kubernetes Deployment deploy

Let's take a look at Deployment, which is the parent object in Kubernetes. A Deployment object is a higher level object than a Replicaset or Pod. In other words, all desired objects can be created through Deployment. And it enables application update or rollback through Deployment object. ​ Then, let's create a Deployment object and deploy it.

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As shown in the figure, Deployment contains Replicaset and Pod objects. In the above figure, Replicaset is maintained with 4 Pods, the Level value is my-nginx, and the target Pod is defined, and detailed Spec is defined in the Container part.

 

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Rather than creating and deploying each object individually in Kubernetes. It is recommended to deploy using this Deployment object, and the advantages of using Deployment are as follows.

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• Defines the criteria to scale in/out of Pods.
• Track all deployed and updated versions of a Pod
• Able to perform rollback on deployed Pods

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Now, let's create a Deployment directory under the test directory, create deployment.yaml, and save the following contents to a file before deploying.

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root@master-VirtualBox:~/test# mkdir deployment root@master-VirtualBox:~/test# cd deployment/ root@master-VirtualBox:~/test/deployment# vi deployment.yaml apiVersion: apps/v1 kind: Deployment ==> define deployed object metadata: name: my-nginx-deployment ==> define name of object spec: selector: matchLabels: run: my-nginx ==> Label vaule of Deployment replicas: 2 ==> quantity of Pod template: metadata: labels: run: my-nginx spec: ==> Spec of Pod containers: - name: my-nginx-container image: nginx imagePullPolicy: Always ports: - containerPort: 80 ​

After inputting and saving as above, we will now deploy the Deployment object through the kubectl command.

root@master-VirtualBox:~/test/deployment# kubectl apply -f deployment.yaml deployment.apps/my-nginx-deployment created ​ root@master-VirtualBox:~/test/deployment# kubectl get deployments NAME READY UP-TO-DATE AVAILABLE AGE my-nginx-deployment 0/2 2 0 26s ​ root@master-VirtualBox:~/test/deployment# kubectl get replicasets NAME DESIRED CURRENT READY AGE my-nginx-deployment-5f85fc96f7 2 2 2 36s ​ root@master-VirtualBox:~/test/deployment# kubectl get pod NAME READY STATUS RESTARTS AGE my-nginx-deployment-5f85fc96f7-s9glk 1/1 Running 0 44s my-nginx-deployment-5f85fc96f7-xv75s 1/1 Running 0 44s

Through the deployment object, both replicaset and pod have been deployed and confirmed that they are in a normal state. ​ Now, let's check whether the replicaset automatically recovers by deleting the Pods arbitrarily.

root@master-VirtualBox:~/test/deployment# kubectl delete pod my-nginx-deployment-5f85fc96f7-s9glk pod "my-nginx-deployment-5f85fc96f7-s9glk" deleted ​ root@master-VirtualBox:~/test/deployment# kubectl get pod NAME READY STATUS RESTARTS AGE my-nginx-deployment-5f85fc96f7-xv75s 1/1 Running 0 6m55s my-nginx-deployment-5f85fc96f7-z7lgs 0/1 ContainerCreating 0 2s

As you can see from the above log, as soon as one Pod is deleted, one is automatically created by Replicast. The reason for the new creation is that 2 was specified in the replica parameter of the Deployment object, so it was newly created to maintain 2 Pods.

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Now, let's use the kubectl command to change the value of the replica of the deployment and query it.

root@master-VirtualBox:~/test/deployment# kubectl edit deployments my-nginx-deployment # Please edit the object below. Lines beginning with a '#' will be ignored, # and an empty file will abort the edit. If an error occurs while saving this file will be # reopened with the relevant failures. # apiVersion: apps/v1 kind: Deployment metadata: annotations: deployment.kubernetes.io/revision: "1" kubectl.kubernetes.io/last-applied-configuration: | {"apiVersion":"apps/v1","kind":"Deployment","metadata":{"annotations":{},"name":"my-nginx-deployment","namespace":"default"},"spec":{"replicas":2,"selector":{"matchLabels":{"run":"my-nginx"}},"template":{"metadata":{"labels":{"run":"my-nginx"}},"spec":{"containers":[{"image":"nginx","imagePullPolicy":"Always","name":"my-nginx-container","ports":[{"containerPort":80}]}]}}}} creationTimestamp: "2022-08-01T04:14:17Z" generation: 2 name: my-nginx-deployment namespace: default resourceVersion: "59837" uid: 448df212-8dc8-42ec-aa90-a7f484bdb974 spec: progressDeadlineSeconds: 600 replicas: 4 revisionHistoryLimit: 10 selector: matchLabels: run: my-nginx strategy:

 

After completing the modification, let's check the information of Pod, Deployment, and Replicaset as shown in the figure below.

root@master-VirtualBox:~/test/deployment# kubectl get deployments.apps NAME READY UP-TO-DATE AVAILABLE AGE my-nginx-deployment 4/4 4 4 13m root@master-VirtualBox:~/test/deployment# root@master-VirtualBox:~/test/deployment# kubectl get replicasets.apps NAME DESIRED CURRENT READY AGE my-nginx-deployment-5f85fc96f7 4 4 4 13m ​ root@master-VirtualBox:~/test/deployment# kubectl get pod NAME READY STATUS RESTARTS AGE my-nginx-deployment-5f85fc96f7-bw48j 1/1 Running 0 113s my-nginx-deployment-5f85fc96f7-mvrvn 1/1 Running 0 113s my-nginx-deployment-5f85fc96f7-xv75s 1/1 Running 0 13m my-nginx-deployment-5f85fc96f7-z7lgs 1/1 Running 0 6m46s

You can see that 2 Pods are being operated while increasing from 2 Pods to 4 Pods. ​ Now, after changing the versions of the deployed Pods, let's go back to the previous version. Change the image of the pod from nginx:latest to nginx:1.9.1, and add change-cause to annotations to record the history of the change. This is in order to inquire with the changed contents in the case of history inquiry later. ​ Open the deployment.yaml file as shown below, modify it as shown in the red part, and save it.

root@master-VirtualBox:~/test/deployment# vi deployment.yaml apiVersion: apps/v1 kind: Deployment metadata: name: my-nginx-deployment annotations: kubernetes.io/change-cause: "set image nginx 1.9.1" spec: selector: matchLabels: run: my-nginx replicas: 4 template: metadata: labels: run: my-nginx spec: containers: - name: my-nginx-container image: nginx:1.9.1 imagePullPolicy: Always ports: - containerPort: 80

Now let's deploy our modified deployment and see the changes.

root@master-VirtualBox:~/test/deployment# kubectl apply -f deployment.yaml root@master-VirtualBox:~/test/deployment# kubectl get deployments ==> deployment의 정보 조회 NAME READY UP-TO-DATE AVAILABLE AGE my-nginx-deployment 4/4 4 4 44m ​ root@master-VirtualBox:~/test/deployment# kubectl get replicasets ==> replicaset의 정보 조회 NAME DESIRED CURRENT READY AGE my-nginx-deployment-5f85fc96f7 0 0 0 44m my-nginx-deployment-d6b6494f6 4 4 4 2m46s ​ root@master-VirtualBox:~/test/deployment# kubectl get pods ==> pod의 정보 조회 NAME READY STATUS RESTARTS AGE my-nginx-deployment-d6b6494f6-5v4xk 1/1 Running 0 26s my-nginx-deployment-d6b6494f6-6nmxk 1/1 Running 0 2m33s my-nginx-deployment-d6b6494f6-dk29d 1/1 Running 0 26s my-nginx-deployment-d6b6494f6-n2f4b 1/1 Running 0 2m53s root@master-VirtualBox:~/test/deployment# kubectl describe pods my-nginx-deployment-d6b6494f6-5v4xk Name: my-nginx-deployment-d6b6494f6-5v4xk Namespace: default Priority: 0 Node: worknode2-virtualbox/192.168.1.6 Start Time: Mon, 01 Aug 2022 13:58:24 +0900 Labels: pod-template-hash=d6b6494f6 run=my-nginx Annotations: cni.projectcalico.org/podIP: 172.16.7.137/32 cni.projectcalico.org/podIPs: 172.16.7.137/32 Status: Running IP: 172.16.7.137 IPs: IP: 172.16.7.137 Controlled By: ReplicaSet/my-nginx-deployment-d6b6494f6 Containers: my-nginx-container: Container ID: containerd://1f041353efe8f49e7de4522032d61bf0ba0b88fe444a6b148ffa34962a85db85 Image: nginx:1.9.1 Image ID: sha256:ee609d78a6476f051fcbf5f3be370c2bb2c5c3b72d05538df0451f9de1604816 Port: 80/TCP Host Port: 0/TCP State: Running Started: Mon, 01 Aug 2022 13:58:30 +0900 Ready: True Restart Count: 0 Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-5kkl2 (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: kube-api-access-5kkl2: Type: Projected (a volume that contains injected data from multiple sources) TokenExpirationSeconds: 3607 ConfigMapName: kube-root-ca.crt ConfigMapOptional: <nil> DownwardAPI: true QoS Class: BestEffort Node-Selectors: <none> Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s node.kubernetes.io/unreachable:NoExecute op=Exists for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 3m58s default-scheduler Successfully assigned default/my-nginx-deployment-d6b6494f6-5v4xk to worknode2-virtualbox Normal Pulling 3m57s kubelet Pulling image "nginx:1.9.1" Normal Pulled 3m53s kubelet Successfully pulled image "nginx:1.9.1" in 4.602785633s Normal Created 3m52s kubelet Created container my-nginx-container Normal Started 3m52s kubelet Started container my-nginx-container

As shown in the picture above, you can see that the image has been changed to 1.9.1 in the red part. ​ Now, let's use the command below to query the revision history of deployment.

root@master-VirtualBox:~/test/deployment# kubectl rollout history deployment deployment.apps/my-nginx-deployment REVISION CHANGE-CAUSE 1 <none> 2 change image nginx 1.9.1 ==> revision 2의 세부 내역을 아래 명령어로 조회 ​ root@master-VirtualBox:~/test/deployment# kubectl rollout history deployment --revision=2 deployment.apps/my-nginx-deployment with revision #2 Pod Template: Labels: pod-template-hash=d6b6494f6 run=my-nginx Annotations: kubernetes.io/change-cause: change image nginx 1.9.1 Containers: my-nginx-container: Image: nginx:1.9.1 Port: 80/TCP Host Port: 0/TCP Environment: <none> Mounts: <none> Volumes: <none>

Now, let's rollback to revision 1, the first version among the results of 'kubectl rollout history deployment'.

root@master-VirtualBox:~/test/deployment# kubectl rollout undo deployment --to-revision=1 deployment.apps/my-nginx-deployment rolled back ​ root@master-VirtualBox:~/test/deployment# kubectl get deployments NAME READY UP-TO-DATE AVAILABLE AGE my-nginx-deployment 4/4 4 4 56m ​ root@master-VirtualBox:~/test/deployment# kubectl get replicasets NAME DESIRED CURRENT READY AGE my-nginx-deployment-5f85fc96f7 4 4 4 57m my-nginx-deployment-d6b6494f6 0 0 0 15m ​ root@master-VirtualBox:~/test/deployment# kubectl get pod NAME READY STATUS RESTARTS AGE my-nginx-deployment-5f85fc96f7-2pd8t 1/1 Running 0 69s my-nginx-deployment-5f85fc96f7-5wj4s 1/1 Running 0 66s my-nginx-deployment-5f85fc96f7-t9s9t 1/1 Running 0 69s my-nginx-deployment-5f85fc96f7-z8wrs 1/1 Running 0 6 ​ root@master-VirtualBox:~/test/deployment# kubectl describe pod my-nginx-deployment-5f85fc96f7-2pd8t Name: my-nginx-deployment-5f85fc96f7-2pd8t Namespace: default Priority: 0 Node: worknode2-virtualbox/192.168.1.6 Start Time: Mon, 01 Aug 2022 14:10:26 +0900 Labels: pod-template-hash=5f85fc96f7 run=my-nginx Annotations: cni.projectcalico.org/podIP: 172.16.7.138/32 cni.projectcalico.org/podIPs: 172.16.7.138/32 Status: Running IP: 172.16.7.138 IPs: IP: 172.16.7.138 Controlled By: ReplicaSet/my-nginx-deployment-5f85fc96f7 Containers: my-nginx-container: Container ID: containerd://8204770b9456cda5faf12aad5438d8893225459c7391a50814b9964c38c7196b Image: nginx Image ID: docker.io/library/nginx@sha256:bd06dfe1f8f7758debd49d3876023992d41842fd8921565aed315a678a309982 Port: 80/TCP Host Port: 0/TCP State: Running Started: Mon, 01 Aug 2022 14:10:29 +0900 Ready: True Restart Count: 0 Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-9jctd (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: kube-api-access-9jctd: Type: Projected (a volume that contains injected data from multiple sources) TokenExpirationSeconds: 3607 ConfigMapName: kube-root-ca.crt ConfigMapOptional: <nil> DownwardAPI: true QoS Class: BestEffort Node-Selectors: <none> Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s node.kubernetes.io/unreachable:NoExecute op=Exists for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 88s default-scheduler Successfully assigned default/my-nginx-deployment-5f85fc96f7-2pd8t to worknode2-virtualbox Normal Pulling 87s kubelet Pulling image "nginx" Normal Pulled 85s kubelet Successfully pulled image "nginx" in 1.927570903s Normal Created 85s kubelet Created container my-nginx-container Normal Started 85s kubelet Started container my-nginx-container root@master-VirtualBox:~/test/deployment# ​

As shown in the picture above, you can confirm that the image has been rolled back to the previous version.