K
Q

Kops/Kubernetes instance group autoscaling

7/14/2017

I have a Kubernetes cluster running in AWS. I used kops to setup and start the cluster.

I defined a minimum and maximum number of nodes in the nodes instance group:

apiVersion: kops/v1alpha2
kind: InstanceGroup
metadata:
  creationTimestamp: 2017-07-03T15:37:59Z
  labels:
    kops.k8s.io/cluster: k8s.tst.test-cluster.com
  name: nodes
spec:
  image: kope.io/k8s-1.6-debian-jessie-amd64-hvm-ebs-2017-05-02
  machineType: t2.large
  maxSize: 7
  minSize: 5
  role: Node
  subnets:
  - eu-central-1b

Currently the cluster has 5 nodes running. After some deployments in the cluster, pods/containers cannot start because there are no nodes available with enough resources.

So I thought, when there is a resource problem, k8s scales automatically the cluster and start more nodes. Because the maximum number of nodes is 7.

Do I miss any configuration?

UPDATE

As @kichik mentioned, the autoscaler addon is already installed. Nevertheless, it doesn't work. Kube-dns is also often restarting because of resource problems.

-- CPA
amazon-web-services
autoscaling
kops
kubectl
kubernetes

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1 Answer

7/14/2017

Someone opened a ticket for this on GitHub and it suggests you have to install the autoscaler addon. Check if it's already installed with:

kubectl get deployments --namespace kube-system | grep autoscaler

If it's not, you can install it with the following script. Make sure AWS_REGION, GROUP_NAME, MIN_NODES and MAX_NODES have the right values.

CLOUD_PROVIDER=aws
IMAGE=gcr.io/google_containers/cluster-autoscaler:v0.5.4
MIN_NODES=5
MAX_NODES=7
AWS_REGION=us-east-1
GROUP_NAME="nodes.k8s.example.com"
SSL_CERT_PATH="/etc/ssl/certs/ca-certificates.crt" # (/etc/ssl/certs for gce)

addon=cluster-autoscaler.yml
wget -O ${addon} https://raw.githubusercontent.com/kubernetes/kops/master/addons/cluster-autoscaler/v1.6.0.yaml

sed -i -e "s@{{CLOUD_PROVIDER}}@${CLOUD_PROVIDER}@g" "${addon}"
sed -i -e "s@{{IMAGE}}@${IMAGE}@g" "${addon}"
sed -i -e "s@{{MIN_NODES}}@${MIN_NODES}@g" "${addon}"
sed -i -e "s@{{MAX_NODES}}@${MAX_NODES}@g" "${addon}"
sed -i -e "s@{{GROUP_NAME}}@${GROUP_NAME}@g" "${addon}"
sed -i -e "s@{{AWS_REGION}}@${AWS_REGION}@g" "${addon}"
sed -i -e "s@{{SSL_CERT_PATH}}@${SSL_CERT_PATH}@g" "${addon}"

kubectl apply -f ${addon}
-- kichik
Source: StackOverflow