Updating an AWS PCS compute node group

This topic provides an overview of available options and describes what to consider when you update an AWS PCS compute node group.

Options for updating an AWS PCS compute node group

Updating an AWS PCS compute node group enables you to change the properties of instances launched by AWS PCS, as well as the rules for how those instances are launched. For example, you can replace the AMI for node group instances with another one with different software installed on it. Or, you can update security groups to change inbound or outbound network connectivity. You can also change the scaling configuration or even change the preferred purchase option to or from Spot instances.

The following node group settings cannot be altered after creation:

• Name

• Instances

Considerations when updating an AWS PCS compute node group

Compute node groups define EC2 instances that are used to process jobs, provide interactive shell access, and other tasks. They are often associated with one or more AWS PCS queues. As you update your compute node group to change its behavior (or that of its nodes), consider the following:

• Changes to compute node group properties become effective when the compute node group status changes from Updating to Active. New instances launch with the updated properties.

• Updates that don't impact the configuration of specific nodes don't affect running nodes. For example, adding a subnet and changing the allocation strategy.

• If you update the launch template for a compute node group, you must update the compute node group to use the new version.

• To add or remove a security group from nodes in a compute node group, edit its launch template and update the compute node group. New instances launch with the updated set of security groups.

• If you directly edit a security group used by a compute node group, it takes immediate effect on running and future instances.

• If you add or remove permissions from the IAM instance profile used by a compute node group, it takes immediate effect on running and future instances.

• To change the AMI used by a compute node group's instances, update the compute node group (or its launch template) to use the new AMI and wait for AWS PCS to replace the instances.

• AWS PCS replaces existing instances in the node group after a node group update operation. If there are jobs running on a node, those jobs are allowed to complete before AWS PCS replaces the node. Interactive user processes (such as on login node instances) are terminated. Node group status returns to Active when AWS PCS marks the instances for replacement, but the actual replacement occurs when the instances are idle.

• If you decrease the maximum number of instances allowed in a compute node group, AWS PCS removes nodes from Slurm to meet the new maximum. AWS PCS terminates running instances associated with the removed Slurm nodes. The running jobs on the removed nodes fail and return to their queues.

• AWS PCS creates a managed launch template for each compute node group. They are named pcs-identifier-do-not-delete. Don't select them when you create or update a compute node group, or the node group will not function correctly.

• If you update a compute node group to use Spot for its purchase option, you must have the AWSServiceRoleForEC2Spot service-linked role in your account. For more information, see Amazon EC2 Spot role for AWS PCS.

To update an AWS PCS compute node group

You can update a node group using the AWS Management Console or the AWS CLI.

AWS Management Console

To update a compute node group

1. Open the AWS PCS console at https://console.aws.amazon.com/pcs/home#/clusters

2. Select the cluster where you wish to update a compute node group.

3. Navigate to Compute node groups, go to the node group you wish to update, then select Edit.

4. In the Computing configuration, Additional settings, and Slurm customization settings sections, update any values except:

   • Instances – You can't change the the instances in a compute node group.

5. Choose Update. The Status field will show Updating while changes are being applied.

   Important

   Compute node group updates can take several minutes.

AWS CLI

To update a compute node group

1. Update your compute node group with the command that follows. Before running the command, make the following replacements:

   1. Replace region-code with the AWS Region that you want to create your cluster in.

   2. Replace my-node-group with the name or computeNodeGroupId for your compute node group.

   3. Replace my-cluster with the name or clusterId of your cluster.

   aws pcs update-compute-node-group --region region-code \
       --cluster-identifier my-cluster \
       --compute-node-group-identifier my-node-group

2. Update any node group parameters except for --instance-configs. For example, to set a new AMI ID, pass --amiId my-custom-ami-id where my-custom-ami-id is replaced by your AMI of choice.

Important

It can take several minutes to update the compute node group.

You can query the status of your node group with the following command.

aws pcs get-compute-node-group --region region-code \
    --cluster-identifier my-cluster \ 
    --compute-node-group-identifier my-node-group