ansible-role-k3s/documentation/quickstart-ha-cluster.md
2022-01-07 13:34:40 -03:00

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# Quickstart: K3s cluster with a HA control plane using embedded etcd
This is the quickstart guide to creating your own 3 node k3s cluster with a
highly available control plane using the embedded etcd datastore.
The control plane will all be workers as well.
:hand: This example requires your Ansible user to be able to connect to the
servers over SSH using key-based authentication. The user is also has an entry
in a sudoers file that allows privilege escalation without requiring a
password.
To test this is the case, run the following check replacing `<ansible_user>`
and `<server_name>`. The expected output is `Works`
`ssh <ansible_user>@<server_name> 'sudo cat /etc/shadow >/dev/null && echo "Works"'`
For example:
```text
[ xmanning@dreadfort:~/git/kubernetes-playground ] (master) $ ssh ansible@kube-0 'sudo cat /etc/shadow >/dev/null && echo "Works"'
Works
[ xmanning@dreadfort:~/git/kubernetes-playground ] (master) $
```
## Directory structure
Our working directory will have the following files:
```text
kubernetes-playground/
|_ inventory.yml
|_ ha_cluster.yml
```
## Inventory
Here's a YAML based example inventory for our servers called `inventory.yml`:
```yaml
---
# We're adding k3s_control_node to each host, this can be done in host_vars/
# or group_vars/ as well - but for simplicity we are setting it here.
k3s_cluster:
hosts:
kube-0:
ansible_user: ansible
ansible_host: 10.10.9.2
ansible_python_interpreter: /usr/bin/python3
k3s_control_node: true
kube-1:
ansible_user: ansible
ansible_host: 10.10.9.3
ansible_python_interpreter: /usr/bin/python3
k3s_control_node: true
kube-2:
ansible_user: ansible
ansible_host: 10.10.9.4
ansible_python_interpreter: /usr/bin/python3
k3s_control_node: true
```
We can test this works with `ansible -i inventory.yml -m ping all`, expected
result:
```text
kube-0 | SUCCESS => {
"changed": false,
"ping": "pong"
}
kube-1 | SUCCESS => {
"changed": false,
"ping": "pong"
}
kube-2 | SUCCESS => {
"changed": false,
"ping": "pong"
}
```
## Playbook
Here is our playbook for the k3s cluster (`ha_cluster.yml`):
```yaml
---
- name: Build a cluster with HA control plane
hosts: k3s_cluster
vars:
k3s_become: true
k3s_etcd_datastore: true
k3s_use_experimental: true # Note this is required for k3s < v1.19.5+k3s1
roles:
- role: xanmanning.k3s
```
## Execution
To execute the playbook against our inventory file, we will run the following
command:
`ansible-playbook -i inventory.yml ha_cluster.yml`
The output we can expect is similar to the below, with no failed or unreachable
nodes. The default behavior of this role is to delegate the first play host as
the primary control node, so kube-0 will have more changed tasks than others:
```text
PLAY RECAP *******************************************************************************************************
kube-0 : ok=53 changed=8 unreachable=0 failed=0 skipped=30 rescued=0 ignored=0
kube-1 : ok=47 changed=10 unreachable=0 failed=0 skipped=28 rescued=0 ignored=0
kube-2 : ok=47 changed=9 unreachable=0 failed=0 skipped=28 rescued=0 ignored=0
```
## Testing
After logging into any of the servers (it doesn't matter), we can test that k3s
is running across the cluster, that all nodes are ready and that everything is
ready to execute our Kubernetes workloads by running the following:
- `sudo kubectl get nodes -o wide`
- `sudo kubectl get pods -o wide --all-namespaces`
:hand: Note we are using `sudo` because we need to be root to access the
kube config for this node. This behavior can be changed with specifying
`write-kubeconfig-mode: '0644'` in `k3s_server`.
**Get Nodes**:
```text
ansible@kube-0:~$ sudo kubectl get nodes -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
kube-0 Ready etcd,master 2m58s v1.19.4+k3s1 10.10.9.2 10.10.9.2 Ubuntu 20.04.1 LTS 5.4.0-56-generic containerd://1.4.1-k3s1
kube-1 Ready etcd,master 2m22s v1.19.4+k3s1 10.10.9.3 10.10.9.3 Ubuntu 20.04.1 LTS 5.4.0-56-generic containerd://1.4.1-k3s1
kube-2 Ready etcd,master 2m10s v1.19.4+k3s1 10.10.9.4 10.10.9.4 Ubuntu 20.04.1 LTS 5.4.0-56-generic containerd://1.4.1-k3s1
```
**Get Pods**:
```text
ansible@kube-0:~$ sudo kubectl get pods -o wide --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
kube-system coredns-66c464876b-rhgn6 1/1 Running 0 3m38s 10.42.0.2 kube-0 <none> <none>
kube-system helm-install-traefik-vwglv 0/1 Completed 0 3m39s 10.42.0.3 kube-0 <none> <none>
kube-system local-path-provisioner-7ff9579c6-d5xpb 1/1 Running 0 3m38s 10.42.0.5 kube-0 <none> <none>
kube-system metrics-server-7b4f8b595-nhbt8 1/1 Running 0 3m38s 10.42.0.4 kube-0 <none> <none>
kube-system svclb-traefik-9lzcq 2/2 Running 0 2m56s 10.42.1.2 kube-1 <none> <none>
kube-system svclb-traefik-vq487 2/2 Running 0 2m45s 10.42.2.2 kube-2 <none> <none>
kube-system svclb-traefik-wkwkk 2/2 Running 0 3m1s 10.42.0.7 kube-0 <none> <none>
kube-system traefik-5dd496474-lw6x8 1/1 Running 0 3m1s 10.42.0.6 kube-0 <none> <none>
```