Create a Kubernetes Cluster

In this step we'll deploy and configure the following:

KinD
Helm
Four-node Kubernetes cluster using KinD
Nginx ingress
Cassandra operator
One-node Cassandra cluster
Java Spring Pet Clinic example app
Connect the Pet Clinic app to the Cassandra cluster

We'll do all the work, you can sit back a relax. However, if you want to understand what all these pieces are, check out the following.

What is KinD?

KinD is a Kubernetes cluster running inside a Docker container. As you know, most people use Kubernetes to manage systems of Docker containers. So, KinD is a Docker container that runs Kubernetes to manage other Docker containers - it's a bit recursive.

We use KinD so we can create a many-node Kubernetes cluster on a single machine. KinD is great because it's relatively light-weight, easy to install and easy to use.

We've already installed KinD for you. For your reference, here are the commands we used to install KinD.

curl -Lo ./kind https://github.com/kubernetes-sigs/kind/releases/download/v0.7.0/kind-$(uname)-amd64
chmod +x ./kind
mv ./kind /usr/local/bin/kind

What is Helm?

Helm is a package manager (like apt or yum) for Kubernetes. Helm allows you to install and update Kubernetes applications. You will notice in the previous command, the sub-command is install followed what we will name the installed package and the chart used to specify the installation. A chart is a specification file we use to tell Helm how to do the installation. Helm downloads the charts from a Helm repo. We'll see more about this later in the course, but you can read more here.

Why do we need a four-node Kubernetes cluster?

First it is important to understand we are working with two types of clusters: a Kubernetes cluster and a Cassandra cluster. The Kubernetes cluster is a set of machines (in this case pseudo-virtual machines inside a Docker container) called Kubernetes nodes. The Cassandra cluster is a set of those Kubernetes nodes that host and run the Cassandra software. From the Kubernetes website: A Kubernetes cluster consists of a set of worker machines, called nodes, that run containerized applications. Every cluster has at least one worker node. We are setting up a four-node Kubernetes cluster so that we have one admin node and three worker nodes. We are using KinD. You can review the KinD cluster configuration in this file.

Open kind-config.yaml

What is an ingress controller and how does it fit into the Kubernetes architecture?

An ingress controller provides access from outside a Kubernetes cluster to the components inside the cluster. We think of a pod as a private network where the containers within the pod are the machines on the pod's network. A common architecture uses a Kubernetes service as a load balancer for one or more pods, where the service has access to the pods' private networks.
Kubernetes maps services' ports to the pods' ports. However, the services' ports are not accessible outside the Kubernetes cluster (with the exception of NodePorts and LoadBalancers, which we will not discuss here). An ingress maps a port on the host machine to a service and its port, thus exposing the service to the outside world.
In our situation, we are running on a Katacoda VM and Katacoda uses a proxy, which gives us a single machine endpoint. So, we will also use the ingress to create URL paths for our services. For example, in this scenario we will use the root path (i.e., /) for the frontend Pet Clinic UI, and /petclinic/api for the Pet Clinic backend microservice.

What is the Cassandra Operator?

The Cassandra Operator simplifies managing your Cassandra cluster in a couple of ways. First, the operator introduces higher level constructs such as datacenters that don't occur in native Kubernetes. Second, the operator monitors your Cassandra cluster to keep it running in a state you specify. If a Cassandra node were to fail, the operator would create a replacement node. If you decide to change the number of nodes in you Cassandra cluster (either increasing or decreasing), the operator manages the change for you. Read more about the Cassandra operator here. Kubernetes operators use two Kubernetes constructs: Custom Resource Definitions (CRD) and Operators. Kubernetes uses CRDs to introduce higher level abstractions (e.g., datacenters) into the Kubernetes system. Operators use these CRDs with domain specific logic to allow you to perform domain specific tasks. Additionally, operators have a control loop which monitors the operators' resources to keep them running in the specified state.

Is the Cassandra Operator the same thing as a Cassandra cluster?

The Kubernetes Cassandra operator is NOT a Cassandra cluster - it's a Kubernetes construct that controls Cassandra clusters. The Kubernetes Cassandra operator performs tasks like monitoring the Cassandra nodes so that if one fails, the operator can replace it. So, once you have Kubernetes Cassandra operator installed, you still need to deploy a Cassandra cluster for the operator to manage. In this example we are deploying a one-node Cassandra cluster. Normally, you would have at least three-nodes in your Cassandra cluster, but for educational purposes (and because of the limited resources within the Katacoda environment) we will only provision a single node.

What is the Pet Clinic app?

The Pet Clinic app is the reference app for the Java Spring frame work. This app manages data for a simple pet clinic business. You can read more here.

What is connecting the Pet Clinic app to Cassandra?

Within the Kubernetes environment, the Cassandra nodes run within their own pods, which are separate from the app pods. So, as the Pet Clinic app initializes, it must establish a connection between its pods and the Cassandra pod. This can take a little bit of time when the Pet Clinic app first starts talking to Cassandra, but after that, the connection is fast.

It's a fair amount of work to configure and deploy all the resources necessary for this scenario, so please be patient as it completes.

Woot! We have the complete Pet Clinic app running.

Click the following to create the KinD cluster.

kind create cluster --name cassandra-kub-cluster --config kind-config.yaml

We use kubectl to interact with the Kubernetes cluster. Let's try it out by inspecting the cluster nodes. Click the following.

watch kubectl get nodes

Once all nodes are Ready, click the following to send a Ctrl-C to exit the watch loop.

^C

Woot! Now we have a Kubernetes cluster and we can talk to it using `kubectl`.

Install an Ingress

Let's add an ingress controller to the cluster.

What is an ingress controller and how does it fit into the Kubernetes architecture?

An ingress controller provides access from outside a Kubernetes cluster to the components inside the cluster. We think of a pod as a private network where the containers within the pod are the machines on the pod's network. A common architecture uses a Kubernetes service as a load balancer for one or more pods, where the service has access to the pods' private networks.
Kubernetes maps services' ports to the pods' ports. However, the services' ports are not accessible outside the Kubernetes cluster (with the exception of NodePorts and LoadBalancers, which we will not discuss here). An ingress maps a port on the host machine to a service and its port, thus exposing the service to the outside world.
In our situation, we are running on a Katacoda VM and Katacoda uses a proxy, which gives us a single machine endpoint. So, we will also use the ingress to create URL paths for our services. For example, in this scenario we will use the root path (i.e., /) for the frontend Pet Clinic UI, and /petclinic/api for the Pet Clinic backend microservice.

Click the following to deploy the ingress controller.

kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/static/provider/kind/deploy.yaml

We need to wait for the ingress controller to completely initialize. Click the following, which will wait until the ingress controller is ready to go.

kubectl wait --namespace ingress-nginx \
  --for=condition=ready pod \
  --selector=app.kubernetes.io/component=controller \
  --timeout=90s

We will configure the ingress for our app when we deploy the app.

Outstanding! We have installed an ingress controller for our Kubernetes cluster.

Install the Cassandra Operator

In this step, we'll install the Kubernetes Cassandra Operator. You can get more details at https://github.com/datastax/cass-operator/tree/v1.4.1/docs/user.

What is a Kubernetes operator?

An operator is like an app in Kubernetes. This app may consist of several related pods, services and components that need to work together. The configuration of these components often requires domain-specific expertise. The Kubernetes operator framework provides a way to codify this domain expertise so the app is easy to install and manage.
The Cassandra Operator provides abstractions (called Custom Resource Definitions, or CRDs) that make it easy to set up a Cassandra cluster. The operator also deploys a pod that runs the CRD control loop. This control loop monitors the Cassandra cluster status and makes the adjustments necessary to keep the cluster running well.

Note: We are working with two types of clusters: a Kubernetes cluster and a Cassandra cluster. The Kubernetes cluster is a set of machines (in this case, because we are using KinD, these are pseudo-virtual machines inside a Docker container) called Kubernetes nodes. The Cassandra cluster is a set of those Kubernetes nodes that host and run the Cassandra software.

Let's lay the groundwork for creating our Cassandra cluster. We want to create a StorageClass where the Cassandra nodes can write and read the data.

What is a Kubernetes StorageClass?

Many Kubernetes resources are stateless and ephemeral, which allows Kubernetes to replace instances of these resources at will. However, this approach cannot support a database. Databases require statefulness, which is what a StorageClass provides. StorageClasses allow you to specify the quality of service for your stateful storage.

Click the following to create the StorageClass.

kubectl apply -f storageclass-kind.yaml

We're going to use Helm to install the Cassandra Operator.

What is Helm?

Helm is a tool that allows us to work at a higher level of abstraction in Kubernetes than using kubectl. It may be helpful to think of kubectl as working at the component level (e.g., services, pods, etc.). Helm works at the app-level of abstraction. We'll use Helm to install Cassandra operator.
Helm uses charts which are like Helm manifests. We find these charts in repos. Our local Helm system keeps track of the Helm repos it knows about, so our first order of business will be to make Helm aware of the repos necessary for the Cassandra operator.

Let's update our list of Helm repos by clicking the following.

helm repo add datastax https://datastax.github.io/charts
helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
helm repo update

Now, with the repos in place, it's easy to install the Cassandra Operator by clicking the following.

helm install cass-operator datastax/cass-operator

Since the people who built the Helm chart for the Cassandra Operator did all the heavy lifting, we trust that the Cassandra install was not too difficult. However, there is a lot that just happened - setting up a stateful app in Kubernetes can be challenging.

Let's wait until the operator is up and running. click the following.

kubectl wait \
  --for=condition=ready pod \
  --selector=name=cass-operator \
  --timeout=90s

We now have the Cassandra operator running, but we don't have a Cassandra cluster yet - we'll do that next.

Excellent! Now you have the Cassandra Kubernetes operator installed!

Deploy Cassandra

In the earlier steps, we created a Kubernetes cluster and installed the Cassandra Operator. In this step, we'll create a single node Cassandra cluster.

We create the Cassandra cluster by applying cassandra-cluster.yaml. If you want to review the manifest, click the following.

Open cassandra-cluster.yaml

What is a Kubernetes manifest?

The genius of Kubernetes is its declarative approach. This means that you define what a system should look like when it's running, and Kubernetes figures out how to make that happen. A Kubernetes manifest is a (yaml) file that describes to Kubernetes the desired state of the system. In this example, the desired state is a single node Cassandra cluster. If we wanted more nodes, all we would need to do is change the spec.size value and apply the manifest.

Create the single-node cluster by clicking the following.

kubectl apply -f cassandra-cluster.yaml

We'll wait for Cassandra to fully initialize by clicking the following (which may require a couple of minutes).

kubectl wait \
  --for=condition=Ready cassandradatacenter/dc1 \
  --timeout=240s

It's that easy! Now you have a running Cassandra cluster.

Deploy the App

Let's deploy our example Pet Clinic app. We'll use a manifest file which you can inspect.

Open petclinic.yaml

As you scroll through the manifest file, you will notice five sections. The first section describes the Pet Clinic backend pod and the second section describes its associated service. Similarly, the third section describes the frontend UI pod and the fourth section describes the service for the frontend. The fifth and last section details the ingress configuration.

Click the following to deploy the app.

kubectl apply -f petclinic.yaml

Let's wait for the app to initialize by clicking the following.

kubectl wait \
  --for=condition=Ready pod \
  --selector=app=petclinic-backend \
  --timeout=90s

With the app running, we can test the backend microservice. Click the following to request a list of pet types from the backend service.

curl localhost:80/petclinic/api/pettypes | jq

The previous query gives us a list of pet types stored in the Cassandra Pet Clinic database. We can access this same query using the UI. Click the following to launch pet clinic in a new tab.

PetClinic

Now, click on the Pet Types tab as shown here.

Pet Types

Clicking on the Pet Types tab causes the front end to issue the same command to the backend as we did in the previous cURL command. You see the results listed in the UI.

Feel free to peruse the other parts of the Pet Clinic app.

Amazing! You have set up a complete cloud-native app using Kubernetes and Cassandra!

Install Proemtheus

With our Kubernetes cluster up and running Cassandra, and the Pet Clinic app, we're ready to start monitoring our system. We'll use Prometheus and Grafana for this.

What is Prometheus?

Prometheus is an app/operator that monitors resources and records the data in a time-series database. Prometheus scrapes data from various resource endpoints (including itself) and stores this data for later review. We can use Prometheus to monitor our hardware, our operating system, out databases and even out apps. We can query this time series data using a query language known as PromQL. If that sounds like too much work, then check out Grafana that allows us to visualize the Prometheus data!

What is Grafana?

Grafana is a visualization tool that often works with Prometheus. In Grafana, we can set up dashboards to allow us to visualize specific metrics with a simple browser-based interface.

There is a lot that goes into setting up the monitoring. We need to install the necessary operators, connect them up and configure them to measure and report the relevant data. Fortunately, we can use another Helm chart to make this easy! Click the following to install and configure Prometheus and Grafana.

helm install monitoring prometheus-community/kube-prometheus-stack -f grafana-config-values.yaml

kubectl create -f dashboards_configmap.yaml

kubectl apply -f prom_service_monitor.yaml
kubectl apply -f petclinic_service_monitor.yaml

Prometheus

Grafana

https://www.youtube.com/watch?v=h4Sl21AKiDg&t=26s

Let's review

Let's review the main points of this learning scenario.

Select all that apply concerning Kubernetes

An ingress controller provides access from outside a Kubernetes cluster to the components inside the cluster

Select all benefits that apply to the Kubernetes Cassandra Operator

With Kubernetes Cassandra Operator installed, I still need to deploy the Cassandra cluster

To deploy an app in Kubernetes, which command do I use? (select one)

What does the `-n` option on the `kubectl` command do? (select one)

cd <directory>	Change directory
ls	List directory
echo 'contents' > <file>	Write contents to a file
cat <file>	Output contents of file

i	In Command Mode	Change into Insert Mode, you can now insert and edit text in the file
esc	In Insert Mode	Change into Command Mode, you can now execute commands
:wq	In Command Mode	Save and Exit

Welcome!

Monitoring - Prometheus and Grafana

Warning: Under Construction

Congratulations!

You've completed the scenario!

Scenario Rating

Steps

Monitoring - Prometheus and Grafana

Create a Kubernetes Cluster

Woot! We have the complete Pet Clinic app running.

Woot! Now we have a Kubernetes cluster and we can talk to it using `kubectl`.

Install an Ingress

Outstanding! We have installed an ingress controller for our Kubernetes cluster.

Install the Cassandra Operator

Excellent! Now you have the Cassandra Kubernetes operator installed!

Deploy Cassandra

It's that easy! Now you have a running Cassandra cluster.

Deploy the App

Amazing! You have set up a complete cloud-native app using Kubernetes and Cassandra!

Install Proemtheus

Let's review

Select all that apply concerning Kubernetes

An ingress controller provides access from outside a Kubernetes cluster to the components inside the cluster

Select all benefits that apply to the Kubernetes Cassandra Operator

With Kubernetes Cassandra Operator installed, I still need to deploy the Cassandra cluster

To deploy an app in Kubernetes, which command do I use? (select one)

What does the `-n` option on the `kubectl` command do? (select one)

Welcome!

Monitoring - Prometheus and Grafana

Warning: Under Construction

Congratulations!

You've completed the scenario!

Scenario Rating

Steps

Monitoring - Prometheus and Grafana

Create a Kubernetes Cluster

Woot! We have the complete Pet Clinic app running.

Woot! Now we have a Kubernetes cluster and we can talk to it using kubectl.

Install an Ingress

Outstanding! We have installed an ingress controller for our Kubernetes cluster.

Install the Cassandra Operator

Excellent! Now you have the Cassandra Kubernetes operator installed!

Deploy Cassandra

It's that easy! Now you have a running Cassandra cluster.

Deploy the App

Amazing! You have set up a complete cloud-native app using Kubernetes and Cassandra!

Install Proemtheus

Let's review

Select all that apply concerning Kubernetes

An ingress controller provides access from outside a Kubernetes cluster to the components inside the cluster

Select all benefits that apply to the Kubernetes Cassandra Operator

With Kubernetes Cassandra Operator installed, I still need to deploy the Cassandra cluster

To deploy an app in Kubernetes, which command do I use? (select one)

What does the -n option on the kubectl command do? (select one)

Help

Vim

Welcome! Connect to start

...or sign up using your email

Sign up using your email

You’ll love Katacoda

Guided Path

Learn By Doing

Stay up-to-date

Welcome back! Connect to start

...or log in using your email

Log in using your email

You’ll love Katacoda

Guided Path

Learn By Doing

Stay up-to-date

Welcome! Enter your email address to connect

😺

Have some feedback for us? Please tell us what's happening so we can improve Katacoda.

Creating Katacoda Scenarios

Running Katacoda Workshops

Debugging Scenarios

Tips

Debug Information

Woot! Now we have a Kubernetes cluster and we can talk to it using `kubectl`.

What does the `-n` option on the `kubectl` command do? (select one)