TripleO based OpenStack deployments use an OpenStack all-in-one node (undercloud) to automate the build and management of the actual cloud (overcloud) using native services such as Heat and Ironic. Roles are used to define services and configuration, which are then applied to specific nodes, for example, Service, Compute and CephStorage, etc.
Although the install is automated, sometimes you need to run adhoc tasks outside of the official update process. For example, you might want to make sure that all hosts are contactable, have a valid subscription (for Red Hat OpenStack Platform), restart containers, or maybe even apply custom changes or patches before an update. Also, during the update process when nodes are being rebooted, it can be useful to use an Ansible script to know when they’ve all come back, services are all running, all containers are healthy, before re-enabling them.
Inventory script
To make this easy, we can use the TripleO Ansible inventory script, which queries the undercloud to get a dynamic inventory of the overcloud nodes. When using the script as an inventory source with the ansible command however, you cannot pass arguments to it. If you’re managing a single cluster and using the standard stack name of overcloud, then this is not a problem; you can just call the script directly.