Creating and managing pods

At the core of Kubernetes is the Pod. Pods represent a logical application and hold a collection of one or more containers and volumes running on the same node. In this chapter you will learn how to:

  • Write a Pod configuration file

  • Create and inspect Pods

  • Interact with Pods remotely using kubectl

In this chapter you will create a Pod named monolith and interact with it using the kubectl command line tool.

Tutorial: Creating Pods

Let’s look at configuration file used to create Kubernetes resources. To see files on your free instance, Cloud Shell provides a code editor. Open it using the pencil button

Pencil button on Cloud Shell bar opens an editor

Now explore the monolith pod configuration file in kubernetes-istio-workshop/manifests/app/pods/monolith.yaml

Editor colorize code and display file outline on the right

Notice some important parts of this Pod definition:

  • you can have more than one container per pod

  • each container have its own image and arguments, and can declare which ports its listen to

  • you should define requests and limits for your container

    • requests specifies minimal resources required by you application

    • limits will protect your cluster for uncontrolled resource consumption by containers

To deploy the monolith pod, use kubectl to apply your pod definition on the cluster :

kubectl apply -f manifests/app/pods/monolith.yaml

Exercise: View Pod details

Use the kubectl get and kubect describe commands to view details for the monolith Pod.

You can also navigate on the Workloads menu in GCP console Workloads menu show running pods and deployments

Hints

kubectl get pods
kubectl describe pods <pod-name>

Quiz

  • What is the IP address of the monolith Pod?

  • What node is the monolith Pod running on?

  • What containers are running in the monolith Pod?

  • What are the labels attached to the monolith Pod?

  • What arguments are set on the monolith container?

Exercise: Interact with a Pod remotely

Pods are allocated a private IP address by default and cannot be reached outside of the cluster. Use the kubectl port-forward command to map a local port to a port inside the monolith pod.

Hints

Use two Cloud Shell terminals. One to run the kubectl port-forward command, and the other to issue curl commands.

kubectl port-forward monolith 10080:80
curl http://127.0.0.1:10080
curl http://127.0.0.1:10080/secure
TOKEN=$( curl -s -u user:password http://127.0.0.1:10080/login | jq -r .token )
curl -H "Authorization: Bearer ${TOKEN}" http://127.0.0.1:10080/secure

Exercise: View the logs of a Pod

Use the kubectl logs command to view the logs for the monolith Pod:

kubectl logs monolith

Use the -f flag and observe what happens.

Bonus: download and use stern for logs

Stern (https://github.com/wercker/stern) is a small go binary which allow to follow logs from multiple pods by pod-name patterns.

Download it from github and make it executable

curl -L -o stern https://github.com/wercker/stern/releases/download/1.11.0/stern_linux_amd64
chmod +x stern

Then you can get logs from pods by pattern:

./stern monoli*

Exercise: Run an interactive shell inside a Pod

Use the kubectl exec command to run an interactive shell inside the monolith Pod:

kubectl exec monolith --stdin --tty -c monolith /bin/sh

List all process running inside this pod:

ps aux

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