Karpenter configuration comes in the form of a Provisioner CRD (Custom Resource Definition). A single Karpenter provisioner is capable of handling many different pod shapes. Karpenter makes scheduling and provisioning decisions based on pod attributes such as labels and affinity. A cluster may have more than one Provisioner, but for the moment we will declare just one: the default Provisioner.
One of the main objectives of Karpenter is to simplify the management of capacity. If you are familiar with other Auto Scalers, you will notice Karpenter takes a different approach. You may have heard the approached referred as group-less auto scaling. Other Solutions have traditionally used the concept of a node group as the element of control that defines the characteristics of the capacity provided (i.e: On-Demand, EC2 Spot, GPU Nodes, etc) and that controls the desired scale of the group in the cluster. In AWS the implementation of a node group matches with Auto Scaling groups. Over time, clusters using this paradigm, that run different type of applications requiring different capacity types, end up with a complex configuration and operational model where node groups must be defined and provided in advance.
Let’s deploy the following configuration:
cat <<EOF | kubectl apply -f -
apiVersion: karpenter.sh/v1alpha5
kind: Provisioner
metadata:
name: default
spec:
labels:
intent: apps
provider:
instanceProfile: KarpenterNodeInstanceProfile-${CLUSTER_NAME}
tags:
accountingEC2Tag: KarpenterDevEnvironmentEC2
ttlSecondsAfterEmpty: 30
EOF
The configuration for this provider is quite simple. We will change in the future the provider. For the moment let’s focus in a few of the settings used.
karpenter.sh/capacity-type
to procure EC2 Spot instances. If nothing provided it will default to on-demand. You can learn which other properties are available here. We will work on a few more during the workshop.Karpenter has been designed to be generic and support other Cloud and Infrastructure providers. At the moment of writing this workshop (Karpenter 0.5.1) main implementation and Provisioner available is on AWS. You can read more about the configuration available for the AWS Provisioner here
You can create a new terminal window within Cloud9 and leave the command below running so you can come back to that terminal every time you want to look for what Karpenter is doing.
To read Karpenter logs from the console you can run the following command.
kubectl logs -f deployment/karpenter-controller -n karpenter
Karpenter log configuration is stored as a Kubernetes ConfigMap. You can read the configuration by running the following command kubectl describe configmap config-logging -n karpenter
. You can increase the logging level to debug
using the following command kubectl patch configmap config-logging -n karpenter --patch '{"data":{"loglevel.controller":"debug"}}'