Deployments, finally we have reached to the last major object in Kubernetes. Deployments take everything we have being doing so far and encapusaltes it. What I mean is the following:

Of course you can have more than 1 pod in replica set. Yes, it is replica set when under Deployment, not replication controller. But the purpose is the same.

So let's create our Deployment now:

To create a deployment again we have two ways:

• Iterative - With kubectl create and so on
• Declarative - Using YML / JSON file, I will be using this one.

As I am bored with the iterative way, let's clean our env and create a deployment. I won't delete my service as I will use it later.

First, let's create our YML file:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-deploy
spec:
  replicas: 10
  selector:
    matchLabels:
      app: hello-date
  template:
    metadata:
      labels:
        app: hello-date
    spec:
      containers:
      - name: hello-pod
        image: andonovj/httpserverdemo:latest
        ports:
        - containerPort: 1234

Bare in mind that the deployment have been moved from extensions/v1beta1 → apps/v1 and forward :) Also a little syntax changes compared to the old one, but nothing serious.

Once we have the YAML file, we can continue as follows:

ubuntu@k8s-master:~$ kubectl create -f deploy.yml
deployment.apps/hello-deploy created
ubuntu@k8s-master:~$ kubectl  get deploy

NAME           READY   UP-TO-DATE   AVAILABLE   AGE
hello-deploy   1/10    10           1           26s
ubuntu@k8s-master:~$ kubectl describe deploy

Name:                   hello-deploy
Namespace:              default
CreationTimestamp:      Sat, 02 May 2020 15:54:34 +0000
Labels:                 <none>
Annotations:            deployment.kubernetes.io/revision: 1
Selector:               app=hello-date
Replicas:               10 desired | 10 updated | 10 total | 10 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=hello-date
  Containers:
   hello-pod:
    Image:        andonovj/httpserverdemo:latest
    Port:         1234/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   hello-deploy-6cd458494 (10/10 replicas created)
Events:
  Type    Reason             Age    From                   Message
  ----    ------             ----   ----                   -------
  Normal  ScalingReplicaSet  8m59s  deployment-controller  Scaled up replica set hello-deploy-6cd458494 to 10

Again, we can check if our app is working:

As already mentioned, deployments operate with Replicat Sets, NOT replication Controllers. Eventhough that is a new objects, it inherits a lot of stuff from the replication controller. You can check the Replica sets, almost the same as the replication controller and notice that we don't have Replication Controllers anymore…after I have deleted them in the past of course.

ubuntu@k8s-master:~$ kubectl get rs
NAME                     DESIRED   CURRENT   READY   AGE
hello-deploy-6cd458494   10        10        10      11m
ubuntu@k8s-master:~$ kubectl get rc
No resources found in default namespace.
ubuntu@k8s-master:~$