Modeling with Provider Trees

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 A, 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.

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)

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