What can a DevOps engineer do to meet these requirements?

Use AWS OpsWorks Stacks to layer the server nodes of that cluster. Create a Chef recipe that populates the content of the /etc/cluster/nodes.config file and restarts the service by using the current members of the layer. Assign that recipe to the Configure lifecycle event.

Put the file nodes.config in version control. Create an AWS CodeDeploy deployment configuration and deployment group based on an Amazon EC2 tag value for the cluster nodes. When adding a new node to the cluster, update the file with all tagged instances, and make a commit in version control. Deploy the new file and restart the services.

Create an Amazon S3 bucket and upload a version of the /etc/cluster/nodes.config file. Create a crontab script that will poll for that S3 file and download it frequently. Use a process manager, such as Monit or systemd, to restart the cluster services when it detects that the new file was modified. When adding a node to the cluster, edit the file’s most recent members. Upload the new file to the S3 bucket.

Create a user data script that lists all members of the current security group of the cluster and automatically updates the /etc/cluster/nodes.config file whenever a new instance is added to the cluster.