AWS Spot Instances

Considerations before configuring Spot pricing

Kubecost uses public pricing from Cloud Service Providers (CSPs) to calculate costs until the actual cloud bill is available, at which point Kubecost will reconcile your Spot prices from your Cost and Usage Report (CUR). This is almost always ready in 48 hours. Most users will likely prefer to configure AWS cloud-integrations instead of configuring the Spot data feed manually as demonstrated in this article.

However, if the majority of costs are due to Spot nodes, it may be useful to configure the Spot pricing data feed as it will increase accuracy for short-term (<48 hour) node costs until the Spot prices from the CUR are available. Note that all other (non-Spot) costs will still be based on public (on-demand) pricing until CUR billing data is reconciled.

Configuring the Spot data feed in Kubecost

With Kubecost, Spot pricing data can be pulled hourly by integrating directly with the AWS Spot feed.

First, to enable the AWS Spot data feed, follow AWS' Spot Instance data feed doc.

While configuring, note the settings used as these values will be needed for the Kubecost configuration.

These values must be set via .Values.kubecostProductConfigs in the Helm chart. If you set any kubecostProductConfigs from the Helm chart, all changes via the front end will be deleted on pod restart.

• projectID the Account ID of the AWS Account on which the Spot nodes are running.

• awsSpotDataRegion region of your Spot data bucket

• awsSpotDataBucket the configured bucket for the Spot data feed

• awsSpotDataPrefix optional configured prefix for your Spot data feed bucket

• spotLabel optional Kubernetes node label name designating whether a node is a Spot node. Used to provide pricing estimates until exact Spot data becomes available from the CUR

• spotLabelValue optional Kubernetes node label value designating a Spot node. Used to provide pricing estimates until exact Spot data becomes available from the CUR. For example, if your Spot nodes carry a label lifecycle:spot, then the spotLabel would be lifecycle and the spotLabelValue would be spot

Spot data feeds are an account level setting, not a payer level. Every AWS Account will have its own Spot data feed. Spot data feed is not currently available in AWS GovCloud.

For Spot data written to an S3 bucket only accessed by Kubecost, it is safe to delete objects after three days of retention.

Configuring IAM

Kubecost requires read access to the Spot data feed bucket. The following IAM policy can be used to grant Kubecost read access to the Spot data feed bucket.

{
  "Version": "2012-10-17",
  "Statement": [
    {
        "Sid": "SpotDataFeed",
        "Effect": "Allow",
        "Action": [
          "s3:ListAllMyBuckets",
          "s3:ListBucket",
          "s3:List*",
          "s3:Get*"
        ],
        "Resource": "arn:aws:s3:::${SpotDataFeedBucketName}*"
    }
  ]
}

To attach the IAM policy to the Kubecost service account, you can use IRSA or the account's service key.

Option 1: IRSA (IAM Roles for Service Accounts)

If your serviceaccount/kubecost-cost-analyzer already has IRSA annotations attached, be sure to include all policies necessary when running this command.

eksctl create iamserviceaccount \
    --name kubecost-cost-analyzer \
    --namespace kubecost \
    --cluster $CLUSTER_NAME --region $REGION_NAME \
    --attach-policy-arn arn:aws:iam::$ACCOUNT_NUMBER:policy/SpotDataFeed \
    --override-existing-serviceaccounts \
    --approve

Option 2: Service Keys

Create a service-key.json as shown:

{
    "aws_access_key_id": "AWS_service_key_aws_access_key_id",
    "aws_secret_access_key": "AWS_service_key_aws_secret_access_key"
}

Create a K8s secret:

$ kubectl create secret generic cloud-service-key --from-file=service-key.json

Set the following Helm config:

kubecostProductConfigs:
  serviceKeySecretName: "cloud-service-key"

Troubleshooting Spot data feed

No Spot instances detected

No spot instances are found in the Spot Data Feed

Verify the below points:

• Make sure data is present in the Spot data feed bucket.

• Make sure Project ID is configured correctly. You can cross-verify the values under Helm values in bug report

• Check the value of kubecost_node_is_spot in Prometheus:

  • "1" means Spot data instance configuration is correct.

  • "0" means not configured properly.

• Is there a prefix? If so, is it configured in Kubecost?

• Make sure the IAM permissions are aligned with https://github.com/kubecost/cloudformation/blob/7feace26637aa2ece1481fda394927ef8e1e3cad/kubecost-single-account-permissions.yaml#L36

• Make sure the Spot data feed bucket has all permissions to access by Kubecost

• The Spot Instance in the Spot data feed bucket should match the instance in the cluster where the Spot data feed is configured. awsSpotDataBucket has to be present in the right cluster.