The Boot Orchestration Service (BOS) creates a session when it is asked to perform an operation on a session template. Sessions provide a way to track the status of many nodes at once as they perform the same operation with the same session template information. When creating a session, both the operation and session template are required parameters.
The v1 version of BOS supports these operations:
BOS sessions can be used to boot compute nodes with customized image roots.
A session requires two parameters, a session template ID and an operation to perform on that template.
The BOS API’s session endpoint can display a list of all of the sessions that have been created, including previous and currently running sessions.
The endpoint can also display the details of a given session when the specific session ID is provided as a parameter. Sessions can also be deleted through the API.
BOS supports a RESTful API. This API can be interacted with directly using tools like cURL. It can also be interacted with through the Cray Command Line Interface (CLI). See Manage a BOS Session for more information.
The Boot Orchestration Agent (BOA) implements each session and sees it through to completion. A BOA is a Kubernetes job. It runs once to completion. If there are transient failures, BOA will exit and Kubernetes will reschedule it so that it can re-execute its session.
BOA moves nodes towards the requested state, but if a node fails during any of the intermediate steps, it takes note of it. BOA will then provide a command in the output of the BOA log that can be used to retry the action. This behavior impacts all BOS operations.
For example, if there is a 6,000 node system and 3 nodes fail to power off during a BOS operation. then BOA will continue and attempt to re-provision the remaining 5,997 nodes. After the command is finished, it will provide information about what the administrator needs to do in order to retry the operation on the 3 nodes that failed.
The following limitations currently exist with BOS sessions: