EKS Placement Group

The EKS placement group customization allows the user to specify placement groups for EKS worker nodes to control their placement strategy within AWS.

This customization will be available when the provider-specific cluster configuration patch is included in the ClusterClass.

What are Placement Groups?

AWS placement groups are logical groupings of instances within a single Availability Zone that influence how instances are placed on underlying hardware. They are useful for:

• Cluster Placement Groups: For applications that benefit from low network latency, high network throughput, or both
• Partition Placement Groups: For large distributed and replicated workloads, such as HDFS, HBase, and Cassandra
• Spread Placement Groups: For applications that have a small number of critical instances that should be kept separate

Configuration

The placement group configuration supports the following field:

Examples

EKS Worker Placement Groups

To specify placement groups for EKS worker nodes:

apiVersion: cluster.x-k8s.io/v1beta1
kind: Cluster
metadata:
  name: <NAME>
spec:
  topology:
    variables:
      - name: workerConfig
        value:
          eks:
            placementGroup:
              name: "eks-worker-pg"

Multiple Node Groups with Different Placement Groups

You can configure different placement groups for different node groups:

apiVersion: cluster.x-k8s.io/v1beta1
kind: Cluster
metadata:
  name: <NAME>
spec:
  topology:
    variables:
      - name: workerConfig
        value:
          eks:
            placementGroup:
              name: "general-worker-pg"
    workers:
      machineDeployments:
        - class: high-performance-worker
          name: md-0
          variables:
            overrides:
              - name: workerConfig
                value:
                  eks:
                    placementGroup:
                      name: "high-performance-pg"
        - class: general-worker
          name: md-1
          variables:
            overrides:
              - name: workerConfig
                value:
                  eks:
                    placementGroup:
                      name: "general-worker-pg"

Resulting EKS Configuration

Applying the placement group configuration will result in the following value being set in the EKS worker node configuration:

• worker AWSMachineTemplate:

  • spec:
      template:
        spec:
          placementGroupName: worker-pg
    

Best Practices

1. Placement Group Types: Choose the appropriate placement group type based on your workload:

   • Cluster: For applications requiring low latency and high throughput
   • Partition: For large distributed workloads that need fault isolation
   • Spread: For critical instances that need maximum availability

2. Naming Convention: Use descriptive names that indicate the purpose and type of the placement group

3. Availability Zone: Placement groups are constrained to a single Availability Zone, so plan your cluster topology accordingly

4. Instance Types: Some instance types have restrictions on placement groups (e.g., some bare metal instances)

5. Capacity Planning: Consider the placement group capacity limits when designing your cluster

6. EKS Node Groups: Consider using different placement groups for different node groups based on workload requirements

Important Notes

• Placement groups must be created in AWS before they can be referenced
• Placement groups are constrained to a single Availability Zone
• You cannot move an existing instance into a placement group
• Some instance types cannot be launched in placement groups
• Placement groups have capacity limits that vary by type and instance family
• EKS managed node groups support placement groups for enhanced networking performance