# Modeling with Provider Trees

## Overview

Placement supports modeling a hierarchical relationship between different resource providers. While a parent provider can have multiple child providers, a child provider can belong to only one parent provider. Therefore, the whole architecture can be considered as a “tree” structure, and the resource provider on top of the “tree” is called a “root provider”. (See the Nested Resource Providers spec for details.)

Modeling the relationship is done by specifying a parent provider via the POST /resource_providers operation when creating a resource provider.

Note

If the parent provider hasn’t been set, you can also parent a resource provider after the creation via the PUT /resource_providers/{uuid} operation. But re-parenting a resource provider is not supported.

The resource providers in a tree – and sharing providers as described in the next section – can be returned in a single allocation request in the response of the GET /allocation_candidates operation. This means that the placement service looks up a resource provider tree in which resource providers can collectively contain all of the requested resources.

This document describes some case studies to explain how sharing providers, aggregates, and traits work if provider trees are involved in the GET /allocation_candidates operation.

## Sharing Resource Providers

Resources on sharing resource providers can be shared by multiple resource provider trees. This means that a sharing provider can be in one allocation request with resource providers from a different tree in the response of the GET /allocation_candidates operation. As an example, this may be used for shared storage that is connected to multiple compute hosts.

Note

Technically, a resource provider with the `MISC_SHARES_VIA_AGGREGATE` trait becomes a sharing resource provider and the resources on it are shared by other resource providers in the same aggregate.

For example, let’s say we have the following environment:

    +-------------------------------+   +-------------------------------+
    | Sharing Storage (SS1)         |   | Sharing Storage (SS2)         |
    |  resources:                   |   |  resources:                   |
    |      DISK_GB: 1000            |   |      DISK_GB: 1000            |
    |  aggregate: [aggA]            |   |  aggregate: []                |
    |  trait:                       |   |  trait:                       |
    |   [MISC_SHARES_VIA_AGGREGATE] |   |   [MISC_SHARES_VIA_AGGREGATE] |
    +---------------+---------------+   +-------------------------------+
                    | Shared via aggA
        +-----------+-----------+           +-----------------------+
        | Compute Node (CN1)    |           | Compute Node (CN2)    |
        |   resources:          |           |   resources:          |
        |      VCPU: 8          |           |      VCPU: 8          |
        |      MEMORY_MB: 1024  |           |      MEMORY_MB: 1024  |
        |      DISK_GB: 1000    |           |      DISK_GB: 1000    |
        |   aggregate: [aggA]   |           |   aggregate: []       |
        |   trait: []           |           |   trait: []           |
        +-----------------------+           +-----------------------+

Assuming no allocations have yet been made against any of the resource providers, the request:

    GET /allocation_candidates?resources=VCPU:1,MEMORY_MB:512,DISK_GB:500

would return three combinations as the allocation candidates.

1. `CN1` (`VCPU`, `MEMORY_MB`, `DISK_GB`)

2. `CN2` (`VCPU`, `MEMORY_MB`, `DISK_GB`)

3. `CN1` (`VCPU`, `MEMORY_MB`) + `SS1` (`DISK_GB`)

`SS2` is also a sharing provider, but not in the allocation candidates because it can’t satisfy the resource itself and it isn’t in any aggregate, so it is not shared by any resource providers.

When a provider tree structure is present, sharing providers are shared by the whole tree if one of the resource providers from the tree is connected to the sharing provider via an aggregate.

For example, let’s say we have the following environment where NUMA resource providers are child providers of the compute host resource providers:

                         +------------------------------+
                         | Sharing Storage (SS1)        |
                         |  resources:                  |
                         |      DISK_GB: 1000           |
                         |  agg: [aggA]                 |
                         |  trait:                      |
                         |   [MISC_SHARES_VIA_AGGREGATE]|
                         +--------------+---------------+
                                        | aggA
    +--------------------------------+  |  +--------------------------------+
    |  +--------------------------+  |  |  |  +--------------------------+  |
    |  | Compute Node (CN1)       |  |  |  |  | Compute Node (CN2)       |  |
    |  |   resources:             +-----+-----+   resources:             |  |
    |  |     MEMORY_MB: 1024      |  |     |  |     MEMORY_MB: 1024      |  |
    |  |     DISK_GB: 1000        |  |     |  |     DISK_GB: 1000        |  |
    |  |   agg: [aggA, aggB]      |  |     |  |   agg: [aggA]            |  |
    |  +-----+-------------+------+  |     |  +-----+-------------+------+  |
    |        | nested      | nested  |     |        | nested      | nested  |
    |  +-----+------+ +----+------+  |     |  +-----+------+ +----+------+  |
    |  | NUMA1_1    | | NUMA1_2   |  |     |  | NUMA2_1    | | NUMA2_2   |  |
    |  |  VCPU: 8   | |  VCPU: 8  |  |     |  |  VCPU: 8   | |  VCPU: 8  |  |
    |  |  agg:[]    | |  agg:[]   |  |     |  |  agg:[aggB]| |  agg:[]   |  |
    |  +------------+ +-----------+  |     |  +------------+ +-----------+  |
    +--------------------------------+     +--------------------------------+

Assuming no allocations have yet been made against any of the resource providers, the request:

    GET /allocation_candidates?resources=VCPU:1,MEMORY_MB:512,DISK_GB:500

would return eight combinations as the allocation candidates.

1. `NUMA1_1` (`VCPU`) + `CN1` (`MEMORY_MB`, `DISK_GB`)

2. `NUMA1_2` (`VCPU`) + `CN1` (`MEMORY_MB`, `DISK_GB`)

3. `NUMA2_1` (`VCPU`) + `CN2` (`MEMORY_MB`, `DISK_GB`)

4. `NUMA2_2` (`VCPU`) + `CN2` (`MEMORY_MB`, `DISK_GB`)

5. `NUMA1_1` (`VCPU`) + `CN1` (`MEMORY_MB`) + `SS1` (`DISK_GB`)

6. `NUMA1_2` (`VCPU`) + `CN1` (`MEMORY_MB`) + `SS1` (`DISK_GB`)

7. `NUMA2_1` (`VCPU`) + `CN2` (`MEMORY_MB`) + `SS1` (`DISK_GB`)

8. `NUMA2_2` (`VCPU`) + `CN2` (`MEMORY_MB`) + `SS1` (`DISK_GB`)

Note that `NUMA1_1` and `SS1`, for example, are not in the same aggregate, but they can be in one allocation request since the tree of `CN1` is connected to `SS1` via aggregate A on `CN1`.

## Filtering Aggregates

What differs between the `CN1` and `CN2` in the example above emerges when you specify the aggregate explicitly in the GET /allocation_candidates operation with the `member_of` query parameter. The `member_of` query parameter accepts aggregate uuids and filters candidates to the resource providers in the given aggregate. See the Filtering by Aggregate Membership spec for details.

Note that the GET /allocation_candidates operation assumes that “an aggregate on a root provider spans the whole tree, while an aggregate on a non-root provider does NOT span the whole tree.”

For example, in the environment above, the request:

    GET /allocation_candidates?resources=VCPU:1,MEMORY_MB:512,DISK_GB:500&member_of=<aggA uuid>

would return eight candidates,

1. `NUMA1_1` (`VCPU`) + `CN1` (`MEMORY_MB`, `DISK_GB`)

2. `NUMA1_2` (`VCPU`) + `CN1` (`MEMORY_MB`, `DISK_GB`)

3. `NUMA2_1` (`VCPU`) + `CN2` (`MEMORY_MB`, `DISK_GB`)

4. `NUMA2_2` (`VCPU`) + `CN2` (`MEMORY_MB`, `DISK_GB`)

5. `NUMA1_1` (`VCPU`) + `CN1` (`MEMORY_MB`) + `SS1` (`DISK_GB`)

6. `NUMA1_2` (`VCPU`) + `CN1` (`MEMORY_MB`) + `SS1` (`DISK_GB`)

7. `NUMA2_1` (`VCPU`) + `CN2` (`MEMORY_MB`) + `SS1` (`DISK_GB`)

8. `NUMA2_2` (`VCPU`) + `CN2` (`MEMORY_MB`) + `SS1` (`DISK_GB`)

This is because aggregate A is on the root providers, `CN1` and `CN2`, so the API assumes the child providers `NUMA1_1`, `NUMA1_2`, `NUMA2_1` and `NUMA2_2` are also in the aggregate A.

Specifying aggregate B:

    GET /allocation_candidates?resources=VCPU:1,MEMORY_MB:512,DISK_GB:500&member_of=<aggB uuid>

would return two candidates.

1. `NUMA1_1` (`VCPU`) + `CN1` (`MEMORY_MB`, `DISK_GB`)

2. `NUMA1_2` (`VCPU`) + `CN1` (`MEMORY_MB`, `DISK_GB`)

This is because `SS1` is not in aggregate B, and because aggregate B on `NUMA2_1` doesn’t span the whole tree since the `NUMA2_1` resource provider isn’t a root resource provider.

## Filtering by Traits

Traits are not only used to indicate sharing providers. They are used to denote capabilities of resource providers. (See The Traits API spec for details.)

Traits can be requested explicitly in the GET /allocation_candidates operation with the `required` query parameter, but traits on resource providers never span other resource providers. If a trait is requested, one of the resource providers that appears in the allocation candidate should have the trait regardless of sharing or nested providers. See the Request Traits spec for details. The `required` query parameter also supports negative expression, via the `!` prefix, for forbidden traits. If a forbidden trait is specified, none of the resource providers that appear in the allocation candidate may have that trait. See the Forbidden Traits spec for details. The `required` parameter also supports the syntax `in:T1,T2,...` which means we are looking for resource providers that have either T1 or T2 traits on them. The two trait query syntax can be combined by repeating the `required` query parameter. So querying providers having (T1 or T2) and T3 and not T4 can be expressed with `required=in:T1,T2&required=T3,!T4`.

For example, let’s say we have the following environment:

    +----------------------------------------------------+
    |  +----------------------------------------------+  |
    |  | Compute Node (CN1)                           |  |
    |  |   resources:                                 |  |
    |  |     VCPU: 8, MEMORY_MB: 1024, DISK_GB: 1000  |  |
    |  |   trait: []                                  |  |
    |  +----------+------------------------+----------+  |
    |             | nested                 | nested      |
    |  +----------+-----------+ +----------+----------+  |
    |  | NIC1_1               | | NIC1_2              |  |
    |  |   resources:         | |   resources:        |  |
    |  |     SRIOV_NET_VF:8   | |     SRIOV_NET_VF:8  |  |
    |  |   trait:             | |   trait:            |  |
    |  |    [HW_NIC_ACCEL_SSL]| |     []              |  |
    |  +----------------------+ +---------------------+  |
    +----------------------------------------------------+

Assuming no allocations have yet been made against any of the resource providers, the request:

    GET /allocation_candidates?resources=VCPU:1,MEMORY_MB:512,DISK_GB:500,SRIOV_NET_VF:2
                              &required=HW_NIC_ACCEL_SSL

would return only `NIC1_1` for `SRIOV_NET_VF`. As a result, we get one candidate.

1. `CN1` (`VCPU`, `MEMORY_MB`, `DISK_GB`) + `NIC1_1` (`SRIOV_NET_VF`)

In contrast, for forbidden traits:

    GET /allocation_candidates?resources=VCPU:1,MEMORY_MB:512,DISK_GB:500,SRIOV_NET_VF:2
                              &required=!HW_NIC_ACCEL_SSL

would exclude `NIC1_1` for `SRIOV_NET_VF`.

1. `CN1` (`VCPU`, `MEMORY_MB`, `DISK_GB`) + `NIC1_2` (`SRIOV_NET_VF`)

If the trait is not in the `required` parameter, that trait will simply be ignored in the GET /allocation_candidates operation.

For example:

    GET /allocation_candidates?resources=VCPU:1,MEMORY_MB:512,DISK_GB:500,SRIOV_NET_VF:2

would return two candidates.

1. `CN1` (`VCPU`, `MEMORY_MB`, `DISK_GB`) + `NIC1_1` (`SRIOV_NET_VF`)

2. `CN1` (`VCPU`, `MEMORY_MB`, `DISK_GB`) + `NIC1_2` (`SRIOV_NET_VF`)

## Granular Resource Requests

If you want to get the same kind of resources from multiple resource providers at once, or if you require a provider of a particular requested resource class to have a specific trait or aggregate membership, you can use the Granular Resource Request feature.

This feature is enabled by numbering the `resources`, `member_of` and `required` query parameters respectively.

For example, in the environment above, the request:

    GET /allocation_candidates?resources=VCPU:1,MEMORY_MB:512,DISK_GB:500
                              &resources1=SRIOV_NET_VF:1&required1=HW_NIC_ACCEL_SSL
                              &resources2=SRIOV_NET_VF:1
                              &group_policy=isolate

would return one candidate where two providers serve `SRIOV_NET_VF` resource.

1. `CN1` (`VCPU`, `MEMORY_MB`, `DISK_GB`) + `NIC1_1` (`SRIOV_NET_VF:1`) + `NIC1_2` (`SRIOV_NET_VF:1`)

The `group_policy=isolate` ensures that the one resource is from a provider with the `HW_NIC_ACCEL_SSL` trait and the other is from another provider with no trait constraints.

If the `group_policy` is set to `none`, it allows multiple granular requests to be served by one provider. Namely:

    GET /allocation_candidates?resources=VCPU:1,MEMORY_MB:512,DISK_GB:500
                              &resources1=SRIOV_NET_VF:1&required1=HW_NIC_ACCEL_SSL
                              &resources2=SRIOV_NET_VF:1
                              &group_policy=none

would return two candidates.

1. `CN1` (`VCPU`, `MEMORY_MB`, `DISK_GB`) + `NIC1_1` (`SRIOV_NET_VF:1`) + `NIC1_2` (`SRIOV_NET_VF:1`)

2. `CN1` (`VCPU`, `MEMORY_MB`, `DISK_GB`) + `NIC1_1` (`SRIOV_NET_VF:2`)

This is because `NIC1_1` satisfies both request 1 (with `HW_NIC_ACCEL_SSL` trait) and request 2 (with no trait constraints).

Note that if `member_of<N>` is specified in granular requests, the API doesn’t assume that “an aggregate on a root provider spans the whole tree.” It just sees whether the specified aggregate is directly associated with the resource provider when looking up the candidates.

## Filtering by Tree

If you want to filter the result by a specific provider tree, use the Filter Allocation Candidates by Provider Tree feature with the `in_tree` query parameter. For example, let’s say we have the following environment:

       +-----------------------+          +-----------------------+
       | Sharing Storage (SS1) |          | Sharing Storage (SS2) |
       |   DISK_GB: 1000       |          |   DISK_GB: 1000       |
       +-----------+-----------+          +-----------+-----------+
                   |                                  |
                   +-----------------+----------------+
                                     | Shared via an aggregate
                   +-----------------+----------------+
                   |                                  |
    +--------------|---------------+   +--------------|--------------+
    | +------------+-------------+ |   | +------------+------------+ |
    | | Compute Node (CN1)       | |   | | Compute Node (CN2)      | |
    | |   DISK_GB: 1000          | |   | |  DISK_GB: 1000          | |
    | +-----+-------------+------+ |   | +----+-------------+------+ |
    |       | nested      | nested |   |      | nested      | nested |
    | +-----+------+ +----+------+ |   | +----+------+ +----+------+ |
    | | NUMA1_1    | | NUMA1_2   | |   | | NUMA2_1   | | NUMA2_2   | |
    | |   VCPU: 4  | |   VCPU: 4 | |   | |  VCPU: 4  | |   VCPU: 4 | |
    | +------------+ +-----------+ |   | +-----------+ +-----------+ |
    +------------------------------+   +-----------------------------+

The request:

    GET /allocation_candidates?resources=VCPU:1,DISK_GB:50&in_tree=<CN1 uuid>

will filter out candidates by `CN1` and return 2 combinations of allocation candidates.

1. `NUMA1_1` (`VCPU`) + `CN1` (`DISK_GB`)

2. `NUMA1_2` (`VCPU`) + `CN1` (`DISK_GB`)

The specified tree can be a non-root provider. The request:

    GET /allocation_candidates?resources=VCPU:1,DISK_GB:50&in_tree=<NUMA1_1 uuid>

will return the same result being aware of resource providers in the same tree with `NUMA1_1` resource provider.

1. `NUMA1_1` (`VCPU`) + `CN1` (`DISK_GB`)

2. `NUMA1_2` (`VCPU`) + `CN1` (`DISK_GB`)

Note

We don’t exclude `NUMA1_2` in the case above. That kind of feature is proposed separately and in progress. See the Support subtree filter specification for details.

The suffixed syntax `in_tree<$S>` (where `$S` is a number in microversions `1.25-1.32` and `[a-zA-Z0-9_-]{1,64}` from `1.33`) is also supported according to Granular Resource Requests. This restricts providers satisfying the suffixed granular request group to the tree of the specified provider.

For example, in the environment above, when you want to have `VCPU` from `CN1` and `DISK_GB` from wherever, the request may look like:

    GET /allocation_candidates?resources=VCPU:1&in_tree=<CN1 uuid>
                              &resources1=DISK_GB:10

which will return the sharing providers as well as the local disk.

1. `NUMA1_1` (`VCPU`) + `CN1` (`DISK_GB`)

2. `NUMA1_2` (`VCPU`) + `CN1` (`DISK_GB`)

3. `NUMA1_1` (`VCPU`) + `SS1` (`DISK_GB`)

4. `NUMA1_2` (`VCPU`) + `SS1` (`DISK_GB`)

5. `NUMA1_1` (`VCPU`) + `SS2` (`DISK_GB`)

6. `NUMA1_2` (`VCPU`) + `SS2` (`DISK_GB`)

This is because the unsuffixed `in_tree` is applied to only the unsuffixed resource of `VCPU`, and not applied to the suffixed resource, `DISK_GB`.

When you want to have `VCPU` from wherever and `DISK_GB` from `SS1`, the request may look like:

    GET /allocation_candidates?resources=VCPU:1
                              &resources1=DISK_GB:10&in_tree1=<SS1 uuid>

which will stick to the first sharing provider for `DISK_GB`.

1. `NUMA1_1` (`VCPU`) + `SS1` (`DISK_GB`)

2. `NUMA1_2` (`VCPU`) + `SS1` (`DISK_GB`)

3. `NUMA2_1` (`VCPU`) + `SS1` (`DISK_GB`)

4. `NUMA2_2` (`VCPU`) + `SS1` (`DISK_GB`)

When you want to have `VCPU` from `CN1` and `DISK_GB` from `SS1`, the request may look like:

    GET /allocation_candidates?resources1=VCPU:1&in_tree1=<CN1 uuid>
                              &resources2=DISK_GB:10&in_tree2=<SS1 uuid>
                              &group_policy=isolate

which will return only 2 candidates.

1. `NUMA1_1` (`VCPU`) + `SS1` (`DISK_GB`)

2. `NUMA1_2` (`VCPU`) + `SS1` (`DISK_GB`)

## Filtering by Root Provider Traits

When traits are associated with a particular resource, the provider tree should be constructed such that the traits are associated with the provider possessing the inventory of that resource. For example, trait `HW_CPU_X86_AVX2` is a trait associated with the `VCPU` resource, so it should be placed on the resource provider with `VCPU` inventory, wherever that provider is positioned in the tree structure. (A NUMA-aware host may model `VCPU` inventory in a child provider, whereas a non-NUMA-aware host may model it in the root provider.)

On the other hand, some traits are associated not with a resource, but with the provider itself. For example, a compute host may be capable of `COMPUTE_VOLUME_MULTI_ATTACH`, or be associated with a `CUSTOM_WINDOWS_LICENSE_POOL`. In this case it is recommended that the root resource provider be used to represent the concept of the “compute host”; so these kinds of traits should always be placed on the root resource provider.

The following environment illustrates the above concepts:

    +---------------------------------+ +-------------------------------------------+
    |+-------------------------------+| |    +-------------------------------+      |
    || Compute Node (NON_NUMA_CN)    || |    | Compute Node (NUMA_CN)        |      |
    ||  VCPU: 8,                     || |    |  DISK_GB: 1000                |      |
    ||  MEMORY_MB: 1024              || |    | traits:                       |      |
    ||  DISK_GB: 1000                || |    |  STORAGE_DISK_SSD,            |      |
    || traits:                       || |    |  COMPUTE_VOLUME_MULTI_ATTACH  |      |
    ||  HW_CPU_X86_AVX2,             || |    +-------+-------------+---------+      |
    ||  STORAGE_DISK_SSD,            || |     nested |             | nested         |
    ||  COMPUTE_VOLUME_MULTI_ATTACH, || |+-----------+-------+ +---+---------------+|
    ||  CUSTOM_WINDOWS_LICENSE_POOL  || || NUMA1             | | NUMA2             ||
    |+-------------------------------+| ||  VCPU: 4          | |  VCPU: 4          ||
    +---------------------------------+ ||  MEMORY_MB: 1024  | |  MEMORY_MB: 1024  ||
                                        ||                   | | traits:           ||
                                        ||                   | |  HW_CPU_X86_AVX2  ||
                                        |+-------------------+ +-------------------+|
                                        +-------------------------------------------+

A tree modeled in this fashion can take advantage of the root_required query parameter to return only allocation candidates from trees which possess (or do not possess) specific traits on their root provider. For example, to return allocation candidates including `VCPU` with the `HW_CPU_X86_AVX2` instruction set from hosts capable of `COMPUTE_VOLUME_MULTI_ATTACH`, a request may look like:

    GET /allocation_candidates
      ?resources1=VCPU:1,MEMORY_MB:512&required1=HW_CPU_X86_AVX2
      &resources2=DISK_GB:100
      &group_policy=none
      &root_required=COMPUTE_VOLUME_MULTI_ATTACH

This will return results from both `NUMA_CN` and `NON_NUMA_CN` because both have the `COMPUTE_VOLUME_MULTI_ATTACH` trait on the root provider; but only `NUMA2` has `HW_CPU_X86_AVX2` so there will only be one result from `NUMA_CN`.

1. `NON_NUMA_CN` (`VCPU`, `MEMORY_MB`, `DISK_GB`)

2. `NUMA_CN` (`DISK_GB`) + `NUMA2` (`VCPU`, `MEMORY_MB`)

To restrict allocation candidates to only those not in your `CUSTOM_WINDOWS_LICENSE_POOL`, a request may look like:

    GET /allocation_candidates
      ?resources1=VCPU:1,MEMORY_MB:512
      &resources2=DISK_GB:100
      &group_policy=none
      &root_required=!CUSTOM_WINDOWS_LICENSE_POOL

This will return results only from `NUMA_CN` because `NON_NUMA_CN` has the forbidden `CUSTOM_WINDOWS_LICENSE_POOL` on the root provider.

1. `NUMA_CN` (`DISK_GB`) + `NUMA1` (`VCPU`, `MEMORY_MB`)

2. `NUMA_CN` (`DISK_GB`) + `NUMA2` (`VCPU`, `MEMORY_MB`)

The syntax of the `root_required` query parameter is identical to that of `required[$S]`: multiple trait strings may be specified, separated by commas, each optionally prefixed with `!` to indicate that it is forbidden.

Note

`root_required` may not be suffixed, and may be specified only once, as it applies only to the root provider.

Note

When sharing providers are involved in the request, `root_required` applies only to the root of the non-sharing provider tree.

Note

While the `required` param supports the any-traits query with the `in:` prefix syntax since microversion 1.39 the `root_required` parameter does not support it yet.

## Filtering by Same Subtree

If you want to express affinity among allocations in separate request groups, use the same_subtree query parameter. It accepts a comma-separated list of request group suffix strings ($S). Each must exactly match a suffix on a granular group somewhere else in the request. If this is provided, at least one of the resource providers satisfying a specified request group must be an ancestor of the rest.

For example, given a model like:

                     +---------------------------+
                     |  Compute Node (CN)        |
                     +-------------+-------------+
                                   |
              +--------------------+-------------------+
              |                                        |
    +-----------+-----------+              +-----------+-----------+
    | NUMA NODE (NUMA0)     |              | NUMA NODE (NUMA1)     |
    |   VCPU: 4             |              |   VCPU: 4             |
    |   MEMORY_MB: 2048     |              |   MEMORY_MB: 2048     |
    | traits:               |              | traits:               |
    |   HW_NUMA_ROOT        |              |   HW_NUMA_ROOT        |
    +-----------+-----------+              +----+-------------+----+
                |                               |             |
    +-----------+-----------+  +----------------+-----+ +-----+----------------+
    | FPGA (FPGA0_0)        |  | FPGA (FPGA1_0)       | | FPGA (FPGA1_1)       |
    |   ACCELERATOR_FPGA:1  |  |   ACCELERATOR_FPGA:1 | |   ACCELERATOR_FPGA:1 |
    | traits:               |  | traits:              | | traits:              |
    |   CUSTOM_TYPE1        |  |   CUSTOM_TYPE1       | |   CUSTOM_TYPE2       |
    +-----------------------+  +----------------------+ +----------------------+

To request FPGAs on the same NUMA node with VCPUs and MEMORY, a request may look like:

    GET /allocation_candidates
      ?resources_COMPUTE=VCPU:1,MEMORY_MB:256
      &resources_ACCEL=ACCELERATOR_FPGA:1
      &group_policy=none
      &same_subtree=_COMPUTE,_ACCEL

This will produce candidates including:

1. `NUMA0` (`VCPU`, `MEMORY_MB`) + `FPGA0_0` (`ACCELERATOR_FPGA`)

2. `NUMA1` (`VCPU`, `MEMORY_MB`) + `FPGA1_0` (`ACCELERATOR_FPGA`)

3. `NUMA1` (`VCPU`, `MEMORY_MB`) + `FPGA1_1` (`ACCELERATOR_FPGA`)

but not:

4. `NUMA0` (`VCPU`, `MEMORY_MB`) + `FPGA1_0` (`ACCELERATOR_FPGA`)

5. `NUMA0` (`VCPU`, `MEMORY_MB`) + `FPGA1_1` (`ACCELERATOR_FPGA`)

6. `NUMA1` (`VCPU`, `MEMORY_MB`) + `FPGA0_0` (`ACCELERATOR_FPGA`)

The request groups specified in the `same_subtree` need not have a resources$S. For example, to request 2 FPGAs with different traits on the same NUMA node, a request may look like:

    GET /allocation_candidates
      ?required_NUMA=HW_NUMA_ROOT
      &resources_ACCEL1=ACCELERATOR_FPGA:1
      &required_ACCEL1=CUSTOM_TYPE1
      &resources_ACCEL2=ACCELERATOR_FPGA:1
      &required_ACCEL2=CUSTOM_TYPE2
      &group_policy=none
      &same_subtree=_NUMA,_ACCEL1,_ACCEL2

This will produce candidates including:

1. `FPGA1_0` (`ACCELERATOR_FPGA`) + `FPGA1_1` (`ACCELERATOR_FPGA`) + `NUMA1`

but not:

2. `FPGA0_0` (`ACCELERATOR_FPGA`) + `FPGA1_1` (`ACCELERATOR_FPGA`) + `NUMA0`

3. `FPGA0_0` (`ACCELERATOR_FPGA`) + `FPGA1_1` (`ACCELERATOR_FPGA`) + `NUMA1`

4. `FPGA1_0` (`ACCELERATOR_FPGA`) + `FPGA1_1` (`ACCELERATOR_FPGA`) + `NUMA0`

The resource provider that satisfies the resourceless request group `?required_NUMA=HW_NUMA_ROOT`, `NUMA1` in the first example above, will not be in the `allocation_request` field of the response, but is shown in the `mappings` field.

The `same_subtree` query parameter can be repeated and each repeat group is treated independently.

this page last updated: 2026-08-19 13:46:50

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