mayalearning / advancedk8forbeginners

Advanced Kubernetes For Beginners

In this workshop we will explore kubernetes beyond simply spinning up a container in a pod.

Before starting

Workshop attendees will receave an email with the instance info prior to the workshop.

Notice that training cloud instances will be available only during the workshop and will be terminated 24 hours later. If you are in our workshop we recommend using the provided cloud instance, you can relax as we have you covered: prerequisites are installed already.

⚡ IMPORTANT NOTE: Everywhere in this repo you see <YOURADDRESS> replace with the URL for the instance you were given.

Table of content and resources

• Workshop On YouTube
• [Presentation](PDF OF SLIDES HERE)
• Discord chat

Title	Description
1 - Getting Connected	Instructions
2 - Control Loop and Operators	Instructions
3 - Custom Resource Definitions (CRD)	Instructions
4 - Sidecars	Instructions
5 - ConfigMap and Secrets	Instructions
6 - Resources	Instructions

1. Getting Connected

✅ Step 1a: The first step in the section.

In your browser window, navigate to the url :3000 where your address is the one provided by Alex.

When you arrive at the webpage you should be greeted by something similar to this.

Click in the Terminal menu from the top of the page and select new terminal as shown below

Once you have opened the terminal run

kubectl get nodes

📃output

NAME                          STATUS   ROLES                  AGE   VERSION
learning-cluster-0-master     Ready    control-plane,master   32m   v1.21.1+k3s1
learning-cluster-0-worker-0   Ready    <none>                 31m   v1.21.1+k3s1
learning-cluster-0-worker-1   Ready    <none>                 31m   v1.21.1+k3s1

If you see the above output you are ready for the lab.

2. Control Loop and Operators

To understand operators a bit more we will use kubectl to apply a pre built operator for the Cassandra database.

kubectl apply -f https://raw.githubusercontent.com/datastax/cass-operator/v1.6.0/docs/user/cass-operator-manifests-v1.19.yaml

📃output

namespace/cass-operator created
serviceaccount/cass-operator created
secret/cass-operator-webhook-config created
customresourcedefinition.apiextensions.k8s.io/cassandradatacenters.cassandra.datastax.com created
clusterrole.rbac.authorization.k8s.io/cass-operator-cr created
clusterrole.rbac.authorization.k8s.io/cass-operator-webhook created
clusterrolebinding.rbac.authorization.k8s.io/cass-operator-crb created
clusterrolebinding.rbac.authorization.k8s.io/cass-operator-webhook created
role.rbac.authorization.k8s.io/cass-operator created
rolebinding.rbac.authorization.k8s.io/cass-operator created
service/cassandradatacenter-webhook-service created
deployment.apps/cass-operator created
validatingwebhookconfiguration.admissionregistration.k8s.io/cassandradatacenter-webhook-registration created   

Screenshot of the above working

3. Custom Resource Definitions (CRD)

Custom resource definitions are ways that you can create assets the function outside of the default kubernetes resource types. This section pulls heavily from the kubernetes custom resource definition examples in the docs.

✅ Step 3a: Setup CRD.

Before getting started check what CRDs are already on the cluster.

kubectl get crd

📃output

NAME                              CREATED AT
addons.k3s.cattle.io              2021-06-17T18:59:23Z
helmcharts.helm.cattle.io         2021-06-17T18:59:23Z
helmchartconfigs.helm.cattle.io   2021-06-17T18:59:23Z

Next apply the yaml for the new custom CRD.

kubectl apply -f crd.yaml

📃output

customresourcedefinition.apiextensions.k8s.io/crontabs.stable.example.com created

Check the list of CRDs again. Notice the new entry for our new asset.

kubectl get crd

📃output

addons.k3s.cattle.io              2021-06-21T15:43:24Z
helmcharts.helm.cattle.io         2021-06-21T15:43:24Z
helmchartconfigs.helm.cattle.io   2021-06-21T15:43:24Z
crontabs.stable.example.com       2021-06-23T16:10:57Z

✅ Step 3b: Setup Pod with the new CRD type.

Start a pod based of the new resource type we defined.

kubectl apply -f example-pod.yaml

📃output

crontab.stable.example.com/my-new-cron-object created

Check for running resources of the type crontab.

kubectl get crontab

📃output

NAME                 AGE
my-new-cron-object   16s

If more information is required running the -o wide flag on the command will provide a full output in yaml format.

kubectl get ct -o yaml

📃output

apiVersion: v1
items:
- apiVersion: stable.example.com/v1
  kind: CronTab
  metadata:
    annotations:
      kubectl.kubernetes.io/last-applied-configuration: |
        {"apiVersion":"stable.example.com/v1","kind":"CronTab","metadata":{"annotations":{},"name":"my-new-cron-object","namespace":"default"},"spec":{"cronSpec":"* * * * */5","image":"my-awesome-cron-image"}}
    creationTimestamp: "2021-06-23T16:11:40Z"
    generation: 1
    name: my-new-cron-object
    namespace: default
    resourceVersion: "157929"
    uid: 43f90a23-13fa-4f60-a673-dc9eff47dc91
  spec:
    cronSpec: '* * * * */5'
    image: my-awesome-cron-image
kind: List
metadata:
  resourceVersion: ""
  selfLink: ""

As illistrated here a custom resource can easily be created allowing for much more expanded pod creation.

4. Sidecars

Much of the credit for this sidecar section goes to this great tutorial on Medium

Before we apply anything lets pull the yaml we will use.

curl -0 https://gist.githubusercontent.com/bbachi/7d6c40fc8f660eed243f7e9cd31d99c8/raw/03801fa846760d7833ad10f0be69552eede7d828/manifest.yml > sidecars.yaml

📃output

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  1478  100  1478    0     0  14211      0 --:--:-- --:--:-- --:--:-- 14211    

If we open up the yaml file in the file explorer we can see that we are setting up three containers. One is a simple Nginx server and two are seperate sidecars. Go ahead and apply the yaml.

Note we are creating a deployment instead of a single pod.

kubectl create -f sidecars.yaml

📃output

deployment.apps/nginx-webapp created
service/nginx-webapp created

Kubernetes will create a deployment object that has every component we just set up inside of it. This deployment object can be created and destroyed by kubectl in a single step.

kubectl get deploy -o wide

📃output

NAME           READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS                                             IMAGES                  SELECTOR
nginx-webapp   5/5     5            5           36s   sidecar-container1,sidecar-container2,main-container   busybox,busybox,nginx   app=nginx-webapp

To see the indavidual pods and ports that are now being used run the following.

kubectl get pods -o wide

📃output

 NAME                           READY   STATUS    RESTARTS   AGE    IP           NODE                          NOMINATED NODE   READINESS GATES
nginx-webapp-f5cf77c9c-8789k   3/3     Running   0          101s   10.244.2.6   learning-cluster-0-worker-1   <none>           <none>
nginx-webapp-f5cf77c9c-rm64k   3/3     Running   0          101s   10.244.0.7   learning-cluster-0-master     <none>           <none>
nginx-webapp-f5cf77c9c-9k9vh   3/3     Running   0          101s   10.244.1.7   learning-cluster-0-worker-0   <none>           <none>
nginx-webapp-f5cf77c9c-d76q8   3/3     Running   0          101s   10.244.2.7   learning-cluster-0-worker-1   <none>           <none>
nginx-webapp-f5cf77c9c-5bfdc   3/3     Running   0          101s   10.244.1.6   learning-cluster-0-worker-0   <none>           <none>

kubectl get svc -o wide

📃output

NAME           TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)        AGE     SELECTOR
kubernetes     ClusterIP   10.43.0.1      <none>        443/TCP        20h     <none>
nginx-webapp   NodePort    10.43.218.89   <none>        80:32711/TCP   2m20s   app=nginx-webapp

We can even see more info if we run the following command.

kubectl cluster-info

📃output

Kubernetes control plane is running at https://127.0.0.1:6443
CoreDNS is running at https://127.0.0.1:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
Metrics-server is running at https://127.0.0.1:6443/api/v1/namespaces/kube-system/services/https:metrics-server:/proxy

To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.

Since everything is running on localhost we can simply go into the container and hit the web server. Replace YOURCONTAINERID with the container ID of the running webapp.

kubectl exec -it YOURCONTAINERID -c main-container -- /bin/sh

Curl isn't installed in this container so we will have to add it. To do so run the following.

apt-get update && apt-get install -y curl

📃output

Get:1 http://security.debian.org/debian-security buster/updates InRelease [65.4 kB]
Get:2 http://deb.debian.org/debian buster InRelease [121 kB]
Get:3 http://deb.debian.org/debian buster-updates InRelease [51.9 kB]
Get:4 http://security.debian.org/debian-security buster/updates/main amd64 Packages [292 kB]
Get:5 http://deb.debian.org/debian buster/main amd64 Packages [7907 kB]
Get:6 http://deb.debian.org/debian buster-updates/main amd64 Packages [10.9 kB]
Fetched 8449 kB in 2s (4806 kB/s)                     
Reading package lists... Done
Reading package lists... Done
Building dependency tree       
Reading state information... Done
curl is already the newest version (7.64.0-4+deb10u2).
0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded.  

Now we can hit the localhost

curl localhost

📃output

...
echo Fri Jun 18 15:31:00 UTC 2021 Hi I am from Sidecar container 1
echo Fri Jun 18 15:31:00 UTC 2021 Hi I am from Sidecar container 2
echo Fri Jun 18 15:31:05 UTC 2021 Hi I am from Sidecar container 1
echo Fri Jun 18 15:31:05 UTC 2021 Hi I am from Sidecar container 2
echo Fri Jun 18 15:31:10 UTC 2021 Hi I am from Sidecar container 1
echo Fri Jun 18 15:31:10 UTC 2021 Hi I am from Sidecar container 2
echo Fri Jun 18 15:31:15 UTC 2021 Hi I am from Sidecar container 1
echo Fri Jun 18 15:31:15 UTC 2021 Hi I am from Sidecar container 2
echo Fri Jun 18 15:31:20 UTC 2021 Hi I am from Sidecar container 1
echo Fri Jun 18 15:31:20 UTC 2021 Hi I am from Sidecar container 2
echo Fri Jun 18 15:31:25 UTC 2021 Hi I am from Sidecar container 1
echo Fri Jun 18 15:31:25 UTC 2021 Hi I am from Sidecar container 2
echo Fri Jun 18 15:31:30 UTC 2021 Hi I am from Sidecar container 1
echo Fri Jun 18 15:31:30 UTC 2021 Hi I am from Sidecar container 2

Exit the containers shell

exit

5. ConfigMap and Secrets

✅ Step 5a: ConfigMaps.

Take a look at what config maps exist on the cluster.

kubectl get cm

📃output

NAME               DATA   AGE
kube-root-ca.crt   1      25h

Use the provided yaml to create a ConfigMap.

kubectl apply -f configmap.yaml

📃output

configmap/configmap-example created

Check to make sure the ConfigMap was created

kubectl get cm

📃output

NAME                DATA   AGE
kube-root-ca.crt    1      25h
configmap-example   4      20s

Next create a pod that consumes the new ConfigMap.

kubectl apply -f configmap_example_pod.yaml

📃output

pod/configmap-demo-pod created

Run describe on the pod and look at the references to the configmap.

kubectl describe pods configmap-demo-pod

📃output

  Name:         configmap-demo-pod
Namespace:    default
...      docker.io/library/alpine@sha256:234cb88d3020898631af0ccbbcca9a66ae7306ecd30c9720690858c1b007d2a0
  ...
    Environment:
      FIRST_ENV:         <set to the key 'first_value' of config map 'configmap-example'>      Optional: false
      ASSET_PROPERTIES:  <set to the key 'app_assets_name' of config map 'configmap-example'>  Optional: false
    Mounts:
      /config from config (ro)
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-cmqfv (ro)
...
Events:
  Type    Reason     Age   From               Message
  ----    ------     ----  ----               -------
  Normal  Scheduled  6s    default-scheduler  Successfully assigned default/configmap-demo-pod to learning-cluster-0-worker-0
  Normal  Pulling    5s    kubelet            Pulling image "alpine"
  Normal  Pulled     4s    kubelet            Successfully pulled image "alpine" in 843.915004ms
  Normal  Created    4s    kubelet            Created container example
  Normal  Started    4s    kubelet            Started container example

6. Resources

For further reading and labs go to More workshops Data On Kubernetes Community and Meetups