A company runs a proprietary in-memory grid that requires updating /etc/cluster/nodes.config whenever cluster membership changes. Adding a node must be automated so the file lists the current member IPs and the service is restarted. What can a DevOps engineer do to automate this with minimal effort?

The correct answer leverages AWS OpsWorks Stacks' ability to manage instance configurations and lifecycle events. OpsWorks layers represent logical groupings of instances, and the Configure lifecycle event is triggered when instances enter or leave the layer. A Chef recipe can be written to dynamically query the layer for its current instances, generate the nodes.config file with their IPs, and then restart the service. This approach automates the entire process with minimal effort and ensures consistency across the cluster. Keeping nodes.config under version control and using CodeDeploy is less efficient because it requires manual updates to the file and a full deployment cycle for every cluster change. Hosting the file in S3 with a cron job introduces polling overhead and potential delays in configuration updates. Using an instance user-data script only runs at launch and wouldn't react to subsequent cluster membership changes.