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Setting up your first cluster with Kubespray

This tutorial walks you through the detailed steps for setting up Kubernetes with Kubespray.

The guide is inspired on the tutorial Kubernetes The Hard Way, with the difference that here we want to showcase how to spin up a Kubernetes cluster in a more managed fashion with Kubespray.

Target Audience

The target audience for this tutorial is someone looking for a hands-on guide to get started with Kubespray.

Cluster Details

Prerequisites

  • Google Cloud Platform: This tutorial leverages the Google Cloud Platform to streamline provisioning of the compute infrastructure required to bootstrap a Kubernetes cluster from the ground up. Sign up for $300 in free credits.
  • Google Cloud Platform SDK: Follow the Google Cloud SDK documentation to install and configure the gcloud command line utility. Make sure to set a default compute region and compute zone.
  • The kubectl command line utility is used to interact with the Kubernetes API Server.
  • Linux or Mac environment with Python 3

Provisioning Compute Resources

Kubernetes requires a set of machines to host the Kubernetes control plane and the worker nodes where containers are ultimately run. In this lab you will provision the compute resources required for running a secure and highly available Kubernetes cluster across a single compute zone.

Networking

The Kubernetes networking model assumes a flat network in which containers and nodes can communicate with each other. In cases where this is not desired network policies can limit how groups of containers are allowed to communicate with each other and external network endpoints.

Setting up network policies is out of scope for this tutorial.

Virtual Private Cloud Network

In this section a dedicated Virtual Private Cloud (VPC) network will be setup to host the Kubernetes cluster.

Create the kubernetes-the-kubespray-way custom VPC network:

gcloud compute networks create kubernetes-the-kubespray-way --subnet-mode custom

A subnet must be provisioned with an IP address range large enough to assign a private IP address to each node in the Kubernetes cluster.

Create the kubernetes subnet in the kubernetes-the-kubespray-way VPC network:

gcloud compute networks subnets create kubernetes \
  --network kubernetes-the-kubespray-way \
  --range 10.240.0.0/24

The 10.240.0.0/24 IP address range can host up to 254 compute instances.

Firewall Rules

Create a firewall rule that allows internal communication across all protocols. It is important to note that the vxlan protocol has to be allowed in order for the calico (see later) networking plugin to work.

gcloud compute firewall-rules create kubernetes-the-kubespray-way-allow-internal \
  --allow tcp,udp,icmp,vxlan \
  --network kubernetes-the-kubespray-way \
  --source-ranges 10.240.0.0/24

Create a firewall rule that allows external SSH, ICMP, and HTTPS:

gcloud compute firewall-rules create kubernetes-the-kubespray-way-allow-external \
  --allow tcp:80,tcp:6443,tcp:443,tcp:22,icmp \
  --network kubernetes-the-kubespray-way \
  --source-ranges 0.0.0.0/0

It is not feasible to restrict the firewall to a specific IP address from where you are accessing the cluster as the nodes also communicate over the public internet and would otherwise run into this firewall. Technically you could limit the firewall to the (fixed) IP addresses of the cluster nodes and the remote IP addresses for accessing the cluster.

Compute Instances

The compute instances in this lab will be provisioned using Ubuntu Server 18.04. Each compute instance will be provisioned with a fixed private IP address and a public IP address (that can be fixed - see guide). Using fixed public IP addresses has the advantage that our cluster node configuration does not need to be updated with new public IP addresses every time the machines are shut down and later on restarted.

Create three compute instances which will host the Kubernetes control plane:

for i in 0 1 2; do
  gcloud compute instances create controller-${i} \
    --async \
    --boot-disk-size 200GB \
    --can-ip-forward \
    --image-family ubuntu-1804-lts \
    --image-project ubuntu-os-cloud \
    --machine-type e2-standard-2 \
    --private-network-ip 10.240.0.1${i} \
    --scopes compute-rw,storage-ro,service-management,service-control,logging-write,monitoring \
    --subnet kubernetes \
    --tags kubernetes-the-kubespray-way,controller
done

Do not forget to fix the IP addresses if you plan on re-using the cluster after temporarily shutting down the VMs - see guide

Create three compute instances which will host the Kubernetes worker nodes:

for i in 0 1 2; do
  gcloud compute instances create worker-${i} \
    --async \
    --boot-disk-size 200GB \
    --can-ip-forward \
    --image-family ubuntu-1804-lts \
    --image-project ubuntu-os-cloud \
    --machine-type e2-standard-2 \
    --private-network-ip 10.240.0.2${i} \
    --scopes compute-rw,storage-ro,service-management,service-control,logging-write,monitoring \
    --subnet kubernetes \
    --tags kubernetes-the-kubespray-way,worker
done

Do not forget to fix the IP addresses if you plan on re-using the cluster after temporarily shutting down the VMs - see guide

List the compute instances in your default compute zone:

gcloud compute instances list --filter="tags.items=kubernetes-the-kubespray-way"

Output

NAME          ZONE        MACHINE_TYPE   PREEMPTIBLE  INTERNAL_IP  EXTERNAL_IP    STATUS
controller-0  us-west1-c  e2-standard-2               10.240.0.10  XX.XX.XX.XXX   RUNNING
controller-1  us-west1-c  e2-standard-2               10.240.0.11  XX.XXX.XXX.XX  RUNNING
controller-2  us-west1-c  e2-standard-2               10.240.0.12  XX.XXX.XX.XXX  RUNNING
worker-0      us-west1-c  e2-standard-2               10.240.0.20  XX.XX.XXX.XXX  RUNNING
worker-1      us-west1-c  e2-standard-2               10.240.0.21  XX.XX.XX.XXX   RUNNING
worker-2      us-west1-c  e2-standard-2               10.240.0.22  XX.XXX.XX.XX   RUNNING

Configuring SSH Access

Kubespray is relying on SSH to configure the controller and worker instances.

Test SSH access to the controller-0 compute instance:

IP_CONTROLLER_0=$(gcloud compute instances list  --filter="tags.items=kubernetes-the-kubespray-way AND name:controller-0" --format="value(EXTERNAL_IP)")
USERNAME=$(whoami)
ssh $USERNAME@$IP_CONTROLLER_0

If this is your first time connecting to a compute instance SSH keys will be generated for you. In this case you will need to enter a passphrase at the prompt to continue.

If you get a 'Remote host identification changed!' warning, you probably already connected to that IP address in the past with another host key. You can remove the old host key by running ssh-keygen -R $IP_CONTROLLER_0

Please repeat this procedure for all the controller and worker nodes, to ensure that SSH access is properly functioning for all nodes.

Set-up Kubespray

The following set of instruction is based on the Quick Start but slightly altered for our set-up.

As Ansible is a python application, we will create a fresh virtual environment to install the dependencies for the Kubespray playbook:

python3 -m venv venv
source venv/bin/activate

Next, we will git clone the Kubespray code into our working directory:

git clone https://github.com/kubernetes-sigs/kubespray.git
cd kubespray
git checkout release-2.17

Now we need to install the dependencies for Ansible to run the Kubespray playbook:

pip install -r requirements.txt

Copy inventory/sample as inventory/mycluster:

cp -rfp inventory/sample inventory/mycluster

Update the sample Ansible inventory file with ip given by gcloud:

gcloud compute instances list --filter="tags.items=kubernetes-the-kubespray-way"

Open inventory/mycluster/inventory.ini file and add it so that controller-0, controller-1 and controller-2 in the kube_control_plane group and worker-0, worker-1 and worker-2 in the kube_node group. Add respective ip to the respective local VPC IP for each node.

The main configuration for the cluster is stored in inventory/mycluster/group_vars/k8s_cluster/k8s_cluster.yml. In this file we will update the supplementary_addresses_in_ssl_keys with a list of the IP addresses of the controller nodes. In that way we can access the kubernetes API server as an administrator from outside the VPC network. You can also see that the kube_network_plugin is by default set to 'calico'. If you set this to 'cloud', it did not work on GCP at the time of testing.

Kubespray also offers to easily enable popular kubernetes add-ons. You can modify the list of add-ons in inventory/mycluster/group_vars/k8s_cluster/addons.yml. Let's enable the metrics server as this is a crucial monitoring element for the kubernetes cluster, just change the 'false' to 'true' for metrics_server_enabled.

Now we will deploy the configuration:

ansible-playbook -i inventory/mycluster/ -u $USERNAME -b -v --private-key=~/.ssh/id_rsa cluster.yml

Ansible will now execute the playbook, this can take up to 20 minutes.

Access the kubernetes cluster

We will leverage a kubeconfig file from one of the controller nodes to access the cluster as administrator from our local workstation.

In this simplified set-up, we did not include a load balancer that usually sits on top of the three controller nodes for a high available API server endpoint. In this simplified tutorial we connect directly to one of the three controllers.

First, we need to edit the permission of the kubeconfig file on one of the controller nodes:

ssh $USERNAME@$IP_CONTROLLER_0
USERNAME=$(whoami)
sudo chown -R $USERNAME:$USERNAME /etc/kubernetes/admin.conf
exit

Now we will copy over the kubeconfig file:

scp $USERNAME@$IP_CONTROLLER_0:/etc/kubernetes/admin.conf kubespray-do.conf

This kubeconfig file uses the internal IP address of the controller node to access the API server. This kubeconfig file will thus not work of from outside the VPC network. We will need to change the API server IP address to the controller node his external IP address. The external IP address will be accepted in the TLS negotiation as we added the controllers external IP addresses in the SSL certificate configuration. Open the file and modify the server IP address from the local IP to the external IP address of controller-0, as stored in $IP_CONTROLLER_0.

Example

apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: XXX
    server: https://35.205.205.80:6443
  name: cluster.local
...

Now, we load the configuration for kubectl:

export KUBECONFIG=$PWD/kubespray-do.conf

We should be all set to communicate with our cluster from our local workstation:

kubectl get nodes

Output

NAME           STATUS   ROLES    AGE   VERSION
controller-0   Ready    master   47m   v1.17.9
controller-1   Ready    master   46m   v1.17.9
controller-2   Ready    master   46m   v1.17.9
worker-0       Ready    <none>   45m   v1.17.9
worker-1       Ready    <none>   45m   v1.17.9
worker-2       Ready    <none>   45m   v1.17.9

Smoke tests

Metrics

Verify if the metrics server addon was correctly installed and works:

kubectl top nodes

Output

NAME           CPU(cores)   CPU%   MEMORY(bytes)   MEMORY%
controller-0   191m         10%    1956Mi          26%
controller-1   190m         10%    1828Mi          24%
controller-2   182m         10%    1839Mi          24%
worker-0       87m          4%     1265Mi          16%
worker-1       102m         5%     1268Mi          16%
worker-2       108m         5%     1299Mi          17%

Please note that metrics might not be available at first and need a couple of minutes before you can actually retrieve them.

Network

Let's verify if the network layer is properly functioning and pods can reach each other:

kubectl run myshell1 -it --rm --image busybox -- sh
hostname -i
# launch myshell2 in separate terminal (see next code block) and ping the hostname of myshell2
ping <hostname myshell2>
kubectl run myshell2 -it --rm --image busybox -- sh
hostname -i
ping <hostname myshell1>

Output

PING 10.233.108.2 (10.233.108.2): 56 data bytes
64 bytes from 10.233.108.2: seq=0 ttl=62 time=2.876 ms
64 bytes from 10.233.108.2: seq=1 ttl=62 time=0.398 ms
64 bytes from 10.233.108.2: seq=2 ttl=62 time=0.378 ms
^C
--- 10.233.108.2 ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 0.378/1.217/2.876 ms

Deployments

In this section you will verify the ability to create and manage Deployments.

Create a deployment for the nginx web server:

kubectl create deployment nginx --image=nginx

List the pod created by the nginx deployment:

kubectl get pods -l app=nginx

Output

NAME                     READY   STATUS    RESTARTS   AGE
nginx-86c57db685-bmtt8   1/1     Running   0          18s

Port Forwarding

In this section you will verify the ability to access applications remotely using port forwarding.

Retrieve the full name of the nginx pod:

POD_NAME=$(kubectl get pods -l app=nginx -o jsonpath="{.items[0].metadata.name}")

Forward port 8080 on your local machine to port 80 of the nginx pod:

kubectl port-forward $POD_NAME 8080:80

Output

Forwarding from 127.0.0.1:8080 -> 80
Forwarding from [::1]:8080 -> 80

In a new terminal make an HTTP request using the forwarding address:

curl --head http://127.0.0.1:8080

Output

HTTP/1.1 200 OK
Server: nginx/1.19.1
Date: Thu, 13 Aug 2020 11:12:04 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 07 Jul 2020 15:52:25 GMT
Connection: keep-alive
ETag: "5f049a39-264"
Accept-Ranges: bytes

Switch back to the previous terminal and stop the port forwarding to the nginx pod:

Forwarding from 127.0.0.1:8080 -> 80
Forwarding from [::1]:8080 -> 80
Handling connection for 8080
^C

Logs

In this section you will verify the ability to retrieve container logs.

Print the nginx pod logs:

kubectl logs $POD_NAME

Output

...
127.0.0.1 - - [13/Aug/2020:11:12:04 +0000] "HEAD / HTTP/1.1" 200 0 "-" "curl/7.64.1" "-"

Exec

In this section you will verify the ability to execute commands in a container.

Print the nginx version by executing the nginx -v command in the nginx container:

kubectl exec -ti $POD_NAME -- nginx -v

Output

nginx version: nginx/1.19.1

Kubernetes services

Expose outside the cluster

In this section you will verify the ability to expose applications using a Service.

Expose the nginx deployment using a NodePort service:

kubectl expose deployment nginx --port 80 --type NodePort

The LoadBalancer service type can not be used because your cluster is not configured with cloud provider integration. Setting up cloud provider integration is out of scope for this tutorial.

Retrieve the node port assigned to the nginx service:

NODE_PORT=$(kubectl get svc nginx \
  --output=jsonpath='{range .spec.ports[0]}{.nodePort}')

Create a firewall rule that allows remote access to the nginx node port:

gcloud compute firewall-rules create kubernetes-the-kubespray-way-allow-nginx-service \
  --allow=tcp:${NODE_PORT} \
  --network kubernetes-the-kubespray-way

Retrieve the external IP address of a worker instance:

EXTERNAL_IP=$(gcloud compute instances describe worker-0 \
  --format 'value(networkInterfaces[0].accessConfigs[0].natIP)')

Make an HTTP request using the external IP address and the nginx node port:

curl -I http://${EXTERNAL_IP}:${NODE_PORT}

Output

HTTP/1.1 200 OK
Server: nginx/1.19.1
Date: Thu, 13 Aug 2020 11:15:02 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 07 Jul 2020 15:52:25 GMT
Connection: keep-alive
ETag: "5f049a39-264"
Accept-Ranges: bytes

Local DNS

We will now also verify that kubernetes built-in DNS works across namespaces. Create a namespace:

kubectl create namespace dev

Create an nginx deployment and expose it within the cluster:

kubectl create deployment nginx --image=nginx -n dev
kubectl expose deployment nginx --port 80 --type ClusterIP -n dev

Run a temporary container to see if we can reach the service from the default namespace:

kubectl run curly -it --rm --image curlimages/curl:7.70.0 -- /bin/sh
curl --head http://nginx.dev:80

Output

HTTP/1.1 200 OK
Server: nginx/1.19.1
Date: Thu, 13 Aug 2020 11:15:59 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 07 Jul 2020 15:52:25 GMT
Connection: keep-alive
ETag: "5f049a39-264"
Accept-Ranges: bytes

Type exit to leave the shell.

Cleaning Up

Kubernetes resources

Delete the dev namespace, the nginx deployment and service:

kubectl delete namespace dev
kubectl delete deployment nginx
kubectl delete svc/nginx

Kubernetes state

Note: you can skip this step if you want to entirely remove the machines.

If you want to keep the VMs and just remove the cluster state, you can simply run another Ansible playbook:

ansible-playbook -i inventory/mycluster/ -u $USERNAME -b -v --private-key=~/.ssh/id_rsa reset.yml

Resetting the cluster to the VMs original state usually takes about a couple of minutes.

Compute instances

Delete the controller and worker compute instances:

gcloud -q compute instances delete \
  controller-0 controller-1 controller-2 \
  worker-0 worker-1 worker-2 \
  --zone $(gcloud config get-value compute/zone)

Network

Delete the fixed IP addresses (assuming you named them equal to the VM names), if any:

gcloud -q compute addresses delete controller-0 controller-1 controller-2 \
  worker-0 worker-1 worker-2

Delete the kubernetes-the-kubespray-way firewall rules:

gcloud -q compute firewall-rules delete \
  kubernetes-the-kubespray-way-allow-nginx-service \
  kubernetes-the-kubespray-way-allow-internal \
  kubernetes-the-kubespray-way-allow-external

Delete the kubernetes-the-kubespray-way network VPC:

gcloud -q compute networks subnets delete kubernetes
gcloud -q compute networks delete kubernetes-the-kubespray-way