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CMB Tenant Hierarchy

Tenants provide a grouping mechanism for jobs submitted on behalf of certain organizations, platforms, or applications. Users can create and organize tenants however best suits their organization or use case. For example, an organization may use a single tenant across several applications or a complex hierarchical structure that matches its team and application ownership structure.

Tenants are associated with a capacity configuration. The capacity configuration defines the amount of compute capacity available to the tenant and provides certain guarantees around isolation from other tenants. The capacity configuration contains weight (used for fair sharing) and resource dimensions.

There are two types of tenants in CMB:

1. Internal Tenants — meant to facilitate the creation of a tree of tenants. Internal tenants’ children can be both internal and leaf tenants. Internal tenants themselves do not accept work and thus do not have associated queues.

2. Leaf Tenants — can accept work and have queues associated with them. Leaf tenants cannot have any children.

With regards to capacity configuration, tenants can use 2 types of capacity:

Reserved Capacity

For internal tenants, if a user specifies reserved capacity, it is fair-shared across the subtree and usable by the leaf tenants under that internal tenant.

For leaf tenants, if a user specifies reserved capacity, it partitions capacity within the hierarchy so that other tenants cannot reserve the same resources. Those reserved resources are not shared with any other tenant, ensuring throughput for a given leaf tenant.

Shared Capacity

The Compute team maintains a global pool of shared capacity that any tenant can burst into, in addition to its reserved capacity. Reservations are not required to use CMB, so a tenant can run out of shared capacity entirely. The pool is fair-shared across tenants, but in CMB, this applied only at admission: CMB had no preemption, so once a job was admitted, it ran to completion regardless of shifts in fair-share demand.

Kueue changes the semantics for both types of capacity, which the fair sharing and preemption section covers.

Here is an example of what a tenant hierarchy looks like:

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