Last update: 10 April 2022
In part I I explained how to setup a high availability k8s masters. In this post, I'm gonna go through the steps to setup the k8s nodes.
A k8s node has two components:
Let's create the VMs
$ vagrant up node1 node2
You should have the node VMs up and running
$ vagrant status
Current machine states:
node1 running (virtualbox)
node2 running (virtualbox)
Let's download kubelet and kube-proxy binaries
$ ansible-playbook k8s-download.yaml
You should get these files in the bin
directory
bin
├── kube-apiserver
├── kube-controller-manager
├── kubelet
├── kube-proxy
└── kube-scheduler
We need to generate certificates for each node using k8s-ca.crt as a root certificate.
Create the PKI certificates
$ ansible-playbook k8s-pki.yaml -t node
The certificates are stored in the pki/k8s
directory
As kubelet
and kube-proxy
need to communicate with the apiserver
, we need to generate certificates for them.
$ ansible-playbook kubeconfig.yaml -t node
The kubeconfig files are stored in the kubeconfig
directory
Deploy node components
$ ansible-playbook k8s-node.yaml
Let's check that the nodes are up and running.
$ kubectl --kubeconfig kubeconfig/admin.kubeconfig get nodes
NAME STATUS ROLES AGE VERSION
k8s-node-1 NotReady <none> 12s v1.23.5
k8s-node-2 NotReady <none> 12s v1.23.5
As you can see, the nodes are up but they are in NotReady
status and that's because there is no network available in the cluster, so let's setup one.
Overlay network can be provided by multiple plugins. You can check the list here.
For this setup, we're gonna use Canal which uses Flannel
for network and calico
for network policies.
$ ansible-playbook canal.yaml
Verification
$ kubectl --kubeconfig kubeconfig/admin.kubeconfig -n kube-system get pods -l k8s-app=canal
NAME READY STATUS RESTARTS AGE
canal-4m27k 2/2 Running 0 2m11s
canal-cslcz 2/2 Running 0 2m11s
Now that we have a cluster network, the nodes should status should turn to Ready
, let's check that
$ kubectl --kubeconfig kubeconfig/admin.kubeconfig get nodes
NAME STATUS ROLES AGE VERSION
k8s-node-1 Ready <none> 91s v1.23.5
k8s-node-2 Ready <none> 91s v1.23.5
Good, the nodes are Ready !
We're gonna use coreDNS plugin as a DNS service provider for our cluster.
$ ansible-playbook coredns.yaml
Verification
$ kubectl --kubeconfig kubeconfig/admin.kubeconfig -n kube-system get pods -l k8s-app=kube-dns
NAME READY STATUS RESTARTS AGE
coredns-7f7bc9686f-fg9kn 1/1 Running 0 30s
The DNS service is now available in the cluster !
So far we have all the components deployed. Let's try to deploy an app to see if everything is working as expected.
Our app is a sime HTTP server that returns "Hello, word!"
$ kubectl --kubeconfig kubeconfig/admin.kubeconfig apply -f app_example.yaml
verification
$ kubectl --kubeconfig kubeconfig/admin.kubeconfig get pods -l app=hello-world-app
NAME READY STATUS RESTARTS AGE
hello-world-app-65d65c94dd-tcpxj 1/1 Running 0 25s
So far the pod is running.
Let's check the DNS record for the service
$ kubectl --kubeconfig kubeconfig/admin.kubeconfig get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
hello-world-app ClusterIP 10.32.0.219 <none> 80/TCP 42s
kubernetes ClusterIP 10.32.0.1 <none> 443/TCP 15m
$ kubectl --kubeconfig kubeconfig/admin.kubeconfig run -i -t busybox --image=alpine --restart=Never
/ # nslookup hello-world-app
Name: hello-world-app
Address 1: 10.32.0.219 hello-world-app.default.svc.cluster.local
So far so good !
Let's now make an HTTP request to the pod to see if it returns something
$ kubectl --kubeconfig kubeconfig/admin.kubeconfig port-forward svc/hello-world-app 8000:80
Open another terminal and run the following command:
$ http 127.0.0.1:8080
HTTP/1.1 200 OK
Content-Length: 72
Content-Type: text/plain; charset=utf-8
Date: Sun, 10 Apr 2022 10:51:58 GMT
Hello, world!
Version: 1.0.0
Hostname: hello-world-app-78468d8f6d-7qnph
Our example app is working as expected 🎉
So far we've deployed a highly available Kubernetes cluster. Now it's time for you to customize it so it fits your needs.
These are some ideas of functionalities that you can add:
Be sure to check the CNCF website to discover some interesting tools.
More posts about Kubernetes are coming soon, stay tuned !
Read more ...