Deploying a single deployment using kustomize and kubectl

As mentioned earlier in the prerequisites we will use kustomize, in combination with kubectl, to deploy things because it makes using multiple decoupled YAML-files easier.

Assuming that you're still in the root folder of the cloned repo do a change of directory:

cd pingpong-service-simple/src/k8s/single-deployment

List the files to see what's in there:

ls -l

You should see something like this:

-rw-r--r--  1 user  group  1119 Dec  8 16:25 deployment.yaml
-rw-r--r--  1 user  group   148 Dec  8 16:34 kustomization.yaml
-rw-r--r--  1 user  group   139 Dec  8 14:54 namespace.yaml

The main file of interest here is kustomization.yaml. It contains a specification of all other files to combine into one big YAML-blob. The Kustomize tool assumes that the file it should go to in order to produce the YAML-blob is called kustomization.yaml so we don't need to type that filename when invoking Kustomize. You can safely type the following in your terminal:

kustomize build .

This will print a large YAML-blob!

Kustomize does not apply anything itself, it simply generates something that you can apply yourself in this case using kubectl.

So go ahead and type in your terminal:

kustomize build . | kubectl apply -f -

It should print something similar to this:

namespace/pingpong created
deployment.apps/pingpong-deployment created

Now go ahead and type:

kubectl get deployments -n pingpong

If you have the Unix command "watch" installed you can do a watch on the above command. That will refresh your view every 2 seconds. This is nice since sometimes it takes a few seconds for things in k8s to become available and then you don't need to repeatedly batter the keyboard looking for an update of the situation. Watch can be installed with brew on a Mac.

Within a couple of seconds you should get something similar to this:

NAME                  READY   UP-TO-DATE   AVAILABLE   AGE
pingpong-deployment   1/1     1            1           15s

Congrats! You've deployed a REST web service to Kubernetes!

Playing around with it a bit

I'm afraid your service is somewhat useless to the world however! So far we've only created a deployment which means that it is not exposed to the Internet. But, since we are connected to our cluster we can still play around with it as if it was, for demonstration purposes. So let's do that!

Connect using kubectl port-forward

The easiest way to connect to the pod inside a deployment is to perform a so called port-forward. It will tie a port on your machine to a port on the pod (which can be considered some sort of virtual machine/being).

To do a port-forward we need the name of the pod in this case, so type:

kubectl get pods -n pingpong

This will show you a list of pods which are the instances of your deployment so to speak, in our case only one, much like the list of deployments we got above:

NAME                                  READY   STATUS    RESTARTS   AGE
pingpong-deployment-5fd978c7b-4md6s   1/1     Running   0          15s

Copy the name of the pod, which is going to be different from the example above, into the following command:

kubectl port-forward -n pingpong <name-of-pod> 8080:8080

The application that we are doing a port forward to is a Spring Boot Application and based on that we know that it uses port 8080. This is also confirmed by the deployment.yaml-file declaring the container and its ports if you don't believe me.

ports:
  - containerPort: 8080

Now you can bring up your favourite browser and navigate to http://localhost:8080/ping. If you've done everything right you should see:

{
  message: "Pong"
}

Check out the logs

To make sure Google is not pulling you leg you can follow the logs of the pod and verify that every call you make results in a Pong message like the one above. To follow the logs type:

kubectl logs -f -n pingpong <name-of-pod>

You should see something similar to this in the logs:

2020-02-15 15:19:22.663 DEBUG 1 --- [nio-8080-exec-3] c.g.s.p.resource.PingResourceController  : Ping complete: PingResource(message=Pong), duration: 0 ms.
2020-02-15 15:19:22.798 DEBUG 1 --- [nio-8080-exec-4] c.g.s.p.resource.PingResourceController  : Ping complete: PingResource(message=Pong), duration: 0 ms.

As you can see the pingpong-service delivers data fast as a lightning strike!

Continue on to learn about how to loadbalance your service