Objective
OVHcloud Managed Kubernetes service provides you Kubernetes clusters without the hassle of installing or operating them. This guide will cover one of the first steps after ordering a cluster: managing nodes and node pools, using the NodePools CRD.
In this guide, we are assuming you’re using the NodePools CRD via kubectl to manage your Kubernetes cluster. If you are using a different method, like the OVHcloud Manager, please refer to the relevant documentation: Managing nodes and node pools guide.
Requirements
- An OVHcloud Managed Kubernetes cluster
- The kubectl command-line tool. You can find the detailed installation instructions for this tool on Kubernetes’ official site.
Nodes and node pools
In your OVHcloud Managed Kubernetes cluster, nodes are grouped in node pools (group of nodes sharing the same configuration).
When you create your cluster, it’s created with a default node pool. Then, you can modify the size of this node pool, or add additional node pools of different sizes and types.
In this guide we explain how to do some basic operations with nodes and node pools using the NodePools CRD: adding nodes to an existing node pool, creating a new node pool…
NodePools CRD
Kubernetes Custom Resources are extensions of the Kubernetes API. Like the default Kubernetes resources, the Custom Resources are endpoints in the Kubernetes API that store collections of API objects of a certain kind. Custom Resources allows to easily extend Kubernetes by adding new features and behaviors.
The simplest way to add a Custom Resource to Kubernetes is to define a CustomResourceDefinition (CRD) with the resource schema.
One of our targets in developing the node pools for OVHcloud Managed Kubernetes was to give our users the capability to fully manage node pools (and by extension nodes themselves) from within Kubernetes, so the logical way to do it was to propose them as Custom Resources in your Kubernetes cluster, by developing the NodePools CRD.
To verify that the NodePools CRD in available in your cluster, do:
# kubectl get crd
You get the list of installed CRDs and inside it the nodepools.kube.cloud.ovh.com
# kubectl get crd
NAME CREATED AT
bgpconfigurations.crd.projectcalico.org 2020-07-26T20:00:00Z
bgppeers.crd.projectcalico.org 2020-07-26T20:00:00Z
blockaffinities.crd.projectcalico.org 2020-07-26T20:00:00Z
clusterinformations.crd.projectcalico.org 2020-07-26T20:00:00Z
felixconfigurations.crd.projectcalico.org 2020-07-26T20:00:00Z
globalnetworkpolicies.crd.projectcalico.org 2020-07-26T20:00:00Z
globalnetworksets.crd.projectcalico.org 2020-07-26T20:00:00Z
hostendpoints.crd.projectcalico.org 2020-07-26T20:00:00Z
ipamblocks.crd.projectcalico.org 2020-07-26T20:00:00Z
ipamconfigs.crd.projectcalico.org 2020-07-26T20:00:00Z
ipamhandles.crd.projectcalico.org 2020-07-26T20:00:00Z
ippools.crd.projectcalico.org 2020-07-26T20:00:00Z
networkpolicies.crd.projectcalico.org 2020-07-26T20:00:00Z
networksets.crd.projectcalico.org 2020-07-26T20:00:00Z
nodepools.kube.cloud.ovh.com 2020-07-26T20:00:22Z
volumesnapshotclasses.snapshot.storage.k8s.io 2020-07-26T20:00:20Z
volumesnapshotcontents.snapshot.storage.k8s.io 2020-07-26T20:00:20Z
volumesnapshots.snapshot.storage.k8s.io 2020-07-26T20:00:20Z
You can get the details of the NodePools CRD by doing:
# kubectl describe crd nodepools.kube.cloud.ovh.com
The most interesting part is the spec of the CRD, describing the NodePool object and its properties:
spec:
description: NodePoolSpec defines the desired state of NodePool
properties:
antiAffinity:
type: boolean
description: If true, all nodes present in the pool will be spawned on different hosts (or hypervisors).
desiredNodes:
description: Represents number of nodes wanted in the pool.
format: int32
maximum: 100
minimum: 0
type: integer
flavor:
description: Represents the flavor nodes wanted in the pool.
type: string
maxNodes:
description: Represents the maximum number of nodes which should be
present in the pool.
format: int32
maximum: 100
minimum: 0
type: integer
minNodes:
description: Represents the minimum number of nodes which should be
present in the pool.
format: int32
maximum: 100
minimum: 0
type: integer
monthlyBilled:
type: boolean
description: If true, all nodes present in the pool will be billed each month (not hourly).
required:
- desiredNodes
- flavor
- maxNodes
- minNodes
type: object
After creation, the desiredNodes can be edited, and the node pool will automatically be resized to accommodate this new value. minNodes and maxNodes can also be edited at any time.
flavor, monthlyBilled and antiAffinity are not editable. Be aware that maxNodes is set by default to 5 when antiAffinity is enabled.
We will later propose cluster autoscaling based on node pols. We see some customer developing they own autoscaling scripts. We strongly encourage you to define minNodes and maxNodes in that case.
Listing node pools
To list node pools, you can use:
# kubectl get nodepools
In my case I have one node pool in my cluster, called my-node-pool, with 2 B2-7 nodes:
# kubectl get nodepools
NAME FLAVOR MONTHLY BILLED ANTI AFFINITY DESIRED CURRENT UP-TO-DATE AVAILABLE MIN MAX AGE
nodepool-b2-7 b2-7 true true 2 2 2 2 0 5 14d
You can see the state of the node pool, how many nodes you want in the pool (DESIRED), how many actually are (CURRENT), how many of them are up-to-date (UP-TO-DATE) and how many are available to be used (AVAILABLE).
Create a node pool
To create a new node pool, you simply need to create a new node pool manifest.
Copy the next YAML manifest in a new-nodepool.yaml file:
apiVersion: kube.cloud.ovh.com/v1alpha1
kind: NodePool
metadata:
name: my-new-node-pool
spec:
antiAffinity: false
desiredNodes: 3
flavor: b2-7
maxNodes: 100
minNodes: 0
monthlyBilled: false
Then apply it to your cluster:
# kubectl apply -f new-nodepool.yaml
Your new node pool will be created:
# kubectl apply -f new-nodepool.yaml nodepool.kube.cloud.ovh.com/my-new-node-pool created # kubectl get nodepools NAME FLAVOR MONTHLY BILLED ANTI AFFINITY DESIRED CURRENT UP-TO-DATE AVAILABLE MIN MAX AGE my-new-node-pool b2-7 false false 3 0 100 3s nodepool-b2-7 b2-7 true true 2 2 2 2 0 5 14d
At the beginning the new node pool is empty, but if you wait a few seconds, you will see how the nodes are progressively created and made available (one after another)…
# kubectl get nodepools
NAME FLAVOR MONTHLY BILLED ANTI AFFINITY DESIRED CURRENT UP-TO-DATE AVAILABLE MIN MAX AGE
my-new-node-pool b2-7 false false 3 3 3 0 100 3s
nodepool-b2-7 b2-7 true true 2 2 2 2 0 5 14d
Editing the node pool size
To upsize or downsize your node pool, you can use simply edit the YAML file and re-apply it. For example, raise the desiredNodes to 5 in new-nodepool.yaml and apply the file:
# kubectl apply -f examples/new-nodepool.yaml nodepool.kube.cloud.ovh.com/my-new-node-pool configured # kubectl get nodepools NAME FLAVOR MONTHLY BILLED ANTI AFFINITY DESIRED CURRENT UP-TO-DATE AVAILABLE MIN MAX AGE my-new-node-pool b2-7 false false 5 3 3 0 100 3s nodepool-b2-7 b2-7 true true 2 2 2 2 0 5 14d
The DESIRED number of nodes has changed, and the two additional nodes will be created.
Then, after some minutes:
# kubectl get nodepools NAME FLAVOR MONTHLY BILLED ANTI AFFINITY DESIRED CURRENT UP-TO-DATE AVAILABLE MIN MAX AGE my-new-node-pool b2-7 false false 5 5 5 3 0 100 3s nodepool-b2-7 b2-7 true true 2 2 2 2 0 5 14d # kubectl get nodepools NAME FLAVOR MONTHLY BILLED ANTI AFFINITY DESIRED CURRENT UP-TO-DATE AVAILABLE MIN MAX AGE my-new-node-pool b2-7 false false 5 5 5 5 0 100 3s nodepool-b2-7 b2-7 true true 2 2 2 2 0 5 14d
You can also use kubectl scale —replicas=X to change the number of desired nodes. For example, let’s resize it back to 2 nodes:
# kubectl scale --replicas=2 nodepool my-new-node-pool
# kubectl scale --replicas=2 nodepool my-new-node-pool nodepool.kube.cloud.ovh.com/my-new-node-pool scaled # kubectl get nodepools NAME FLAVOR MONTHLY BILLED ANTI AFFINITY DESIRED CURRENT UP-TO-DATE AVAILABLE MIN MAX AGE my-new-node-pool b2-7 false false 2 5 5 5 0 100 3s nodepool-b2-7 b2-7 true true 2 2 2 2 0 5 14d
Then, after some minutes:
# kubectl get nodepools
NAME FLAVOR MONTHLY BILLED ANTI AFFINITY DESIRED CURRENT UP-TO-DATE AVAILABLE MIN MAX AGE
my-new-node-pool b2-7 false false 2 2 2 2 0 100 3s
nodepool-b2-7 b2-7 true true 2 2 2 2 0 5 14d
Deleting a node pool
You can simply use kubectl to delete a node pool, as any other Kubernetes resource:
# kubectl delete nodepool my-new-node-pool
Go further
To have an overview of OVHcloud Managed Kubernetes service, you can go to the OVHcloud Managed Kubernetes site.
Otherwise to skip it and push to deploy your first application on your Kubernetes cluster, we invite you to follow our guide to deploying an application.