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3. Deploy App

This file will cover how to...

  • Create a deployment imperatively
  • View deployments
  • View pods
  • Scale deployments
  • Create a deployment imperatively
  • Delete a deployment

Create Deployment Imperatively

If you do not currently have a cluster running, you will need to go back through "Create a Cluster".

To check if you have a cluster running:

kubectl get nodes

In order to deploy our cookieapp imperatively, you will need to provide the deployment name and the app's image. In this case, the deployment will be named cookie-factory and the image will be the image we built and saved locally called cookieapp.

kubectl create deployment cookie-factory --image=cookieapp:v1

This command searches for a node that can be used to run our app and then scheduled the cookieapp to run on that node.

View Deployments

To see your deployment:

kubectl get deployments

There should only be one deployment and it should state that it's a available to run the image on.

View Pods

To see the single pod we have on our deployment:

kubectl get pods

There should only be one pod running. If we delete this pod, the deployment will start a new pod in its place.

Try it out:

kubectl delete pods --all

then:

kubectl get pods

You should see the previous pod is being terminated or has already been terminated and a new pod has been created in its place.

View Replicas

To see the ReplicaSet created by the Deployment:

kubectl get rs

This command will show:

  1. The desired number of replicas of the application which is defined when the Deployment is created.
  2. The current number of replicas are the number of replicas that are currently running the application.

Scale Up and Down

To scale the Deployment to 4 replicas:

kubectl scale deployments/cookie-factory --replicas=4

To list the deployments again to see the updated desired number of replicas:

kubectl get deployments

To check that the number of Pods has changed:

kubectl get pods -o wide

Each pod has a different IP address. To check the changes in the Deployment events log:

kubectl describe deployments/cookie-factory

To scale the Service back down to 2 replicas:

kubectl scale deployments/cookie-factory --replicas=2

To check that the change was applied, get deployments again:

kubectl get deployments

And check the number of replicas by getting the pods again:

kubectl get pods -o wide

Create Deployment Declaratively

We can also create a deployment using a yaml file. here is a file name declarative.yml in this package with instructions to create a deployment named "other-cookie-app" using the same docker image.

To create a deployment with this yam file:

kubectl apply -f declarative.yml

Now we can view deployments again:

kubectl get deployments

And also our new pods:

kubectl get pods

Delete Deployment

We can delete either deployment.

kubectl delete deployments other-cookie-app

Next: Shell

Once you've completed the steps in this file, continue to learn how to expose your deployment and run a proxy to access it.