Pool Object¶

A Pool defines membership rules and lifecycle transitions for a group of Machine objects. Pools provide a structured way to manage machine allocation, ensuring that machines move through well-defined states with appropriate configuration applied at each transition. Pools are static configuration objects that can be shared through content packs and version sets; actual membership is determined dynamically from each machine's Pool and PoolStatus fields.

Machines in a pool progress through a defined set of states: Joining, HoldJoin, Free, Building, HoldBuild, InUse, Destroying, HoldDestroy, Leaving, and HoldLeave. The "Hold" states provide pause points where operator intervention or external approval can gate transitions. A machine entering the pool starts in Joining, becomes Free when ready for allocation, moves to InUse when allocated to a consumer, and transitions through Leaving when released back.

Each state transition can trigger a set of PoolTransitionActions that automatically configure the machine:

• EnterActions -- applied when a machine joins the pool
• AllocateActions -- applied when a free machine is allocated
• ReleaseActions -- applied when an in-use machine is released
• ExitActions -- applied when a machine leaves the pool

Each PoolTransitionActions structure can set a Workflow to run, add or remove Profile references, and add or remove parameters. This allows pools to drive machines through provisioning workflows on entry and decommissioning workflows on exit without manual intervention.

Pools support hierarchical organization through the ParentPool field. When a machine exits a child pool, it returns to the parent pool rather than becoming unmanaged. The AutoFill configuration enables dynamic pool scaling: when the number of free machines drops below MinFree, the system can automatically acquire machines from an AcquirePool or create new ones using CreateParameters, and return excess machines when free count exceeds MaxFree.

Pools work with Resource Broker objects that can dynamically create and destroy machines (for example, provisioning cloud VMs or spinning up containers) to satisfy pool demand.

Fields¶