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ansible-role-k3s/documentation/operations/shrinking-a-cluster.md

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Shrinking a cluster

This document describes the method for shrinking a cluster, by removing a worker nodes.

Assumptions

It is assumed that you have already deployed a k3s cluster using this role, you have an appropriately configured inventory and playbook to create the cluster.

Below, our example inventory and playbook are as follows:

  • inventory: inventory.yml
  • playbook: cluster.yml

Currently your inventory.yml looks like this, it has three nodes defined, kube-0 (control node) and kube-1, kube-2 (worker nodes).

---

k3s_cluster:
  hosts:
    kube-0:
      ansible_user: ansible
      ansible_host: 10.10.9.2
      ansible_python_interpreter: /usr/bin/python3
    kube-1:
      ansible_user: ansible
      ansible_host: 10.10.9.3
      ansible_python_interpreter: /usr/bin/python3
    kube-2:
      ansible_user: ansible
      ansible_host: 10.10.9.4
      ansible_python_interpreter: /usr/bin/python3

Method

We have our three nodes, one control, two workers. The goal is to shrink this to remove excess capacity by offboarding the worker node kube-2. To do this we will set kube-2 node to k3s_state: uninstalled in our inventory.

---

k3s_cluster:
  hosts:
    kube-0:
      ansible_user: ansible
      ansible_host: 10.10.9.2
      ansible_python_interpreter: /usr/bin/python3
    kube-1:
      ansible_user: ansible
      ansible_host: 10.10.9.3
      ansible_python_interpreter: /usr/bin/python3
    kube-2:
      ansible_user: ansible
      ansible_host: 10.10.9.4
      ansible_python_interpreter: /usr/bin/python3
      k3s_state: uninstalled

What you will typically see is changes to your control plane (kube-0) and the node being removed (kube-2). The role will register the removal of the node with the cluster by draining the node and removing it from the cluster.

PLAY RECAP *******************************************************************************************************
kube-0                     : ok=55   changed=2    unreachable=0    failed=0    skipped=28   rescued=0    ignored=0
kube-1                     : ok=40   changed=0    unreachable=0    failed=0    skipped=35   rescued=0    ignored=0
kube-2                     : ok=23   changed=2    unreachable=0    failed=0    skipped=17   rescued=0    ignored=1