How to handle Deployments Using Kubernetes Engine on Google Cloud Platform

9 min readJul 5, 2022

A BLOG BY KUSHA VARUN

Overview

Dev Ops practices will regularly make use of multiple deployments to manage application deployment scenarios such as “Continuous Deployment”, “Blue-Green Deployments”, “Canary Deployments” and more. This lab is to provide practice in scaling and managing containers so you can accomplish these common scenarios where multiple heterogeneous deployments are being used.

What you’ll do

Practice with kubectl tool
Create deployment YAML files
Launch, update, and scale deployments
Practice updating deployments and deployment styles

Prerequisites

Linux System Administration skills
DevOps theory: concepts of continuous deployment

Introduction to deployments

Heterogeneous deployments typically involve connecting two or more distinct infrastructure environments or regions to address a specific technical or operational need. Heterogeneous deployments are called “hybrid”, “multi-cloud”, or “public-private”, depending upon the specifics of the deployment. For this lab, heterogeneous deployments include those that span regions within a single cloud environment, multiple public cloud environments (multi-cloud), or a combination of on-premises and public cloud environments (hybrid or public-private).

Various business and technical challenges can arise in deployments that are limited to a single environment or region:

Maxed out resources: In any single environment, particularly in on-premises environments, you might not have the compute, networking, and storage resources to meet your production needs.
Limited geographic reach: Deployments in a single environment require people who are geographically distant from one another to access one deployment. Their traffic might travel around the world to a central location.
Limited availability: Web-scale traffic patterns challenge applications to remain fault-tolerant and resilient.
Vendor lock-in: Vendor-level platform and infrastructure abstractions can prevent you from porting applications.
Inflexible resources: Your resources might be limited to a particular set of computing, storage, or networking offerings.

Heterogeneous deployments can help address these challenges, but they must be architected using programmatic and deterministic processes and procedures. One-off or ad-hoc deployment procedures can cause deployments or processes to be brittle and intolerant of failures. Ad-hoc processes can lose data or drop traffic. Good deployment processes must be repeatable and use proven approaches for managing the provisioning, configuration, and maintenance.

Three common scenarios for heterogeneous deployment are multi-cloud deployments, fronting on-premises data, and continuous integration/continuous delivery (CI/CD) processes.

The following exercises practice some common use cases for heterogeneous deployments, along with well-architected approaches using Kubernetes and other infrastructure resources to accomplish them.

Learn about the deployment object

Let’s get started with Deployments. First, let’s take a look at the Deployment object. The explain command in kubectl can tell us about the Deployment object.

kubectl explain deployment

We can also see all of the fields using the --recursive option.

kubectl explain deployment --recursive

You can use the explain command as you go through the lab to help you understand the structure of a Deployment object and understand what the individual fields do.

kubectl explain deployment.metadata.name

Create a deployment

Update the deployments/auth.yaml configuration file:

vi deployments/auth.yaml

Start the editor:

Change the image in the containers section of the Deployment to the following:

...
containers:
- name: auth
  image: "kelseyhightower/auth:1.0.0"
...

Save the auth.yaml file: press <Esc> then type:

:wq

Press <Enter>. Now let's create a simple deployment. Examine the deployment configuration file:

cat deployments/auth.yaml

(Output)

apiVersion: apps/v1
kind: Deployment
metadata:
  name: auth
spec:
  replicas: 1
  selector:
    matchLabels:
      app: auth
  template:
    metadata:
      labels:
        app: auth
        track: stable
    spec:
      containers:
        - name: auth
          image: "kelseyhightower/auth:1.0.0"
          ports:
            - name: http
              containerPort: 80
            - name: health
              containerPort: 81
...

Notice how the Deployment is creating one replica and it’s using version 1.0.0 of the auth container.

When you run the kubectl create command to create the auth deployment, it will make one pod that conforms to the data in the Deployment manifest. This means we can scale the number of Pods by changing the number specified in the replicas field.

Go ahead and create your deployment object using kubectl create:

kubectl create -f deployments/auth.yaml

Once you have created the Deployment, you can verify that it was created.

kubectl get deployments

Once the deployment is created, Kubernetes will create a ReplicaSet for the Deployment. We can verify that a ReplicaSet was created for our Deployment:

kubectl get replicasets

We should see a ReplicaSet with a name like auth-xxxxxxx

Finally, we can view the Pods that were created as part of our Deployment. The single Pod is created by the Kubernetes when the ReplicaSet is created.

kubectl get pods

It’s time to create a service for our auth deployment. You’ve already seen service manifest files, so we won’t go into the details here. Use the kubectl create command to create the auth service.

kubectl create -f services/auth.yaml

Now, do the same thing to create and expose the hello Deployment.

kubectl create -f deployments/hello.yaml
kubectl create -f services/hello.yaml

And one more time to create and expose the frontend Deployment.

kubectl create secret generic tls-certs --from-file tls/
kubectl create configmap nginx-frontend-conf --from-file=nginx/frontend.conf
kubectl create -f deployments/frontend.yaml
kubectl create -f services/frontend.yaml

Note: You created a ConfigMap for the frontend.

Interact with the front end by grabbing its external IP and then curling to it.

kubectl get services frontend

It may take a few seconds before the External-IP field is populated for your service. This is normal. Just re-run the above command every few seconds until the field is populated.

curl -ks https://<EXTERNAL-IP>

And you get the hello response back.

You can also use the output templating feature kubectl to use curl as a one-liner:

curl -ks https://`kubectl get svc frontend -o=jsonpath="{.status.loadBalancer.ingress[0].ip}"`

Scale a Deployment

Now that we have a Deployment created, we can scale it. Do this by updating the spec.replicas field. You can look at an explanation of this field using the kubectl explain command again.

kubectl explain deployment.spec.replicas

The replicas field can be most easily updated using the kubectl scale command:

kubectl scale deployment hello --replicas=5

Note: It may take a minute or so for all the new pods to start up.

After the Deployment is updated, Kubernetes will automatically update the associated ReplicaSet and start new Pods to make the total number of Pods equal to 5.

Verify that there are now 5 hello Pods running:

kubectl get pods | grep hello- | wc -l

Now scale back the application:

kubectl scale deployment hello --replicas=3

Again, verify that you have the correct number of Pods.

kubectl get pods | grep hello- | wc -l

You learned about Kubernetes deployments and how to manage & scale a group of Pods.

Rolling update

Deployments support updating images to a new version through a rolling update mechanism. When a Deployment is updated with a new version, it creates a new ReplicaSet and slowly increases the number of replicas in the new ReplicaSet as it decreases the replicas in the old ReplicaSet.

Trigger a rolling update

To update your Deployment, run the following command:

kubectl edit deployment hello

Change the image in the containers section of the Deployment to the following:

...
containers:
  image: kelseyhightower/hello:2.0.0
...

Save and exit.

Once you save out of the editor, the updated Deployment will be saved to your cluster and Kubernetes will begin a rolling update.

See the new ReplicaSet that Kubernetes creates.:

kubectl get replicaset

You can also see a new entry in the rollout history:

kubectl rollout history deployment/hello

Pause a rolling update

If you detect problems with a running rollout, pause it to stop the update. Give that a try now:

kubectl rollout pause deployment/hello

Verify the current state of the rollout:

kubectl rollout status deployment/hello

You can also verify this on the Pods directly:

kubectl get pods -o jsonpath --template='{range .items[*]}{.metadata.name}{"\t"}{"\t"}{.spec.containers[0].image}{"\n"}{end}'

Resume a rolling update

The rollout is paused which means that some pods are at the new version and some pods are at the older version. We can continue the rollout using the resume command.

kubectl rollout resume deployment/hello

When the rollout is complete, you should see the following when running the status command.

kubectl rollout status deployment/hello

(Output)

deployment "hello" successfully rolled out

Rollback an update

Assume that a bug was detected in your new version. Since the new version is presumed to have problems, any users connected to the new Pods will experience those issues.

You will want to roll back to the previous version so you can investigate and then release a version that is fixed properly.

Use the rollout command to roll back to the previous version:

kubectl rollout undo deployment/hello

Verify the roll back in the history:

kubectl rollout history deployment/hello

Finally, verify that all the Pods have rolled back to their previous versions:

kubectl get pods -o jsonpath --template='{range .items[*]}{.metadata.name}{"\t"}{"\t"}{.spec.containers[0].image}{"\n"}{end}'

Great! You learned about rolling updates for Kubernetes deployments and how to update applications without downtime.

Canary deployments

When you want to test a new deployment in production with a subset of your users, use a canary deployment. Canary deployments allow you to release a change to a small subset of your users to mitigate the risk associated with new releases.

Blue-green deployments

Rolling updates are ideal because they allow you to deploy an application slowly with minimal overhead, minimal performance impact, and minimal downtime. There are instances where it is beneficial to modify the load balancers to point to that new version only after it has been fully deployed. In this case, blue-green deployments are the way to go.

Kubernetes achieves this by creating two separate deployments; one for the old “blue” version and one for the new “green” version. Use your existing hello deployment for the "blue" version. The deployments will be accessed via a Service that will act as the router. Once the new "green" version is up and running, you'll switch over to using that version by updating the Service.

A major downside of blue-green deployments is that you will need to have at least 2x the resources in your cluster necessary to host your application. Make sure you have enough resources in your cluster before deploying both versions of the application at once.

The service

Use the existing hello service, but update it so that it has a selector app:hello, version: 1.0.0. The selector will match the existing "blue" deployment. But it will not match the "green" deployment because it will use a different version.

First, update the service:

kubectl apply -f services/hello-blue.yaml

NOTE: Ignore the warning that says resource service/hello is missing this is patched automatically.

Updating using Blue-Green Deployment

To support a blue-green deployment style, we will create a new “green” deployment for our new version. The green deployment updates the version label and the image path.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-green
spec:
  replicas: 3
  selector:
    matchLabels:
      app: hello
  template:
    metadata:
      labels:
        app: hello
        track: stable
        version: 2.0.0
    spec:
      containers:
        - name: hello
          image: kelseyhightower/hello:2.0.0
          ports:
            - name: http
              containerPort: 80
            - name: health
              containerPort: 81
          resources:
            limits:
              cpu: 0.2
              memory: 10Mi
          livenessProbe:
            httpGet:
              path: /healthz
              port: 81
              scheme: HTTP
            initialDelaySeconds: 5
            periodSeconds: 15
            timeoutSeconds: 5
          readinessProbe:
            httpGet:
              path: /readiness
              port: 81
              scheme: HTTP
            initialDelaySeconds: 5
            timeoutSeconds: 1

Create the green deployment:

kubectl create -f deployments/hello-green.yaml

Once you have a green deployment and it has started up properly, verify that the current version of 1.0.0 is still being used:

curl -ks https://`kubectl get svc frontend -o=jsonpath="{.status.loadBalancer.ingress[0].ip}"`/version

Now, update the service to point to the new version:

kubectl apply -f services/hello-green.yaml

When the service is updated, the “green” deployment will be used immediately. You can now verify that the new version is always being used.

curl -ks https://`kubectl get svc frontend -o=jsonpath="{.status.loadBalancer.ingress[0].ip}"`/version

Blue-Green Rollback

If necessary, you can roll back to the old version in the same way. While the “blue” deployment is still running, just update the service back to the old version.

kubectl apply -f services/hello-blue.yaml

Once you have updated the service, your rollback will have been successful. Again, verify that the right version is now being used:

curl -ks https://`kubectl get svc frontend -o=jsonpath="{.status.loadBalancer.ingress[0].ip}"`/version

You did it! You learned about blue-green deployments and how to deploy updates to applications that need to switch versions all at once.