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.
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,
NUMA1_1(VCPU) +CN1(MEMORY_MB,DISK_GB)NUMA1_2(VCPU) +CN1(MEMORY_MB,DISK_GB)NUMA2_1(VCPU) +CN2(MEMORY_MB,DISK_GB)NUMA2_2(VCPU) +CN2(MEMORY_MB,DISK_GB)NUMA1_1(VCPU) +CN1(MEMORY_MB) +SS1(DISK_GB)NUMA1_2(VCPU) +CN1(MEMORY_MB) +SS1(DISK_GB)NUMA2_1(VCPU) +CN2(MEMORY_MB) +SS1(DISK_GB)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.
NUMA1_1(VCPU) +CN1(MEMORY_MB,DISK_GB)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.
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.
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.
CN1(VCPU,MEMORY_MB,DISK_GB) +NIC1_1(SRIOV_NET_VF)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.
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.
CN1(VCPU,MEMORY_MB,DISK_GB) +NIC1_1(SRIOV_NET_VF:1) +NIC1_2(SRIOV_NET_VF:1)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.
NUMA1_1(VCPU) +CN1(DISK_GB)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.
NUMA1_1(VCPU) +CN1(DISK_GB)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.
NUMA1_1(VCPU) +CN1(DISK_GB)NUMA1_2(VCPU) +CN1(DISK_GB)NUMA1_1(VCPU) +SS1(DISK_GB)NUMA1_2(VCPU) +SS1(DISK_GB)NUMA1_1(VCPU) +SS2(DISK_GB)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.
NUMA1_1(VCPU) +SS1(DISK_GB)NUMA1_2(VCPU) +SS1(DISK_GB)NUMA2_1(VCPU) +SS1(DISK_GB)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.
NUMA1_1(VCPU) +SS1(DISK_GB)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.
NON_NUMA_CN(VCPU,MEMORY_MB,DISK_GB)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.
NUMA_CN(DISK_GB) +NUMA1(VCPU,MEMORY_MB)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 ($S). Each must exactly match a suffix on a granular group somewhere else in the request. If this is provided, at least one of the resource providers satisfying a specified request group must be an ancestor of the rest.
For example, given a model like:
+---------------------------+
| Compute Node (CN) |
+-------------+-------------+
|
+--------------------+-------------------+
| |
+-----------+-----------+ +-----------+-----------+
| NUMA NODE (NUMA0) | | NUMA NODE (NUMA1) |
| VCPU: 4 | | VCPU: 4 |
| MEMORY_MB: 2048 | | MEMORY_MB: 2048 |
| traits: | | traits: |
| HW_NUMA_ROOT | | HW_NUMA_ROOT |
+-----------+-----------+ +----+-------------+----+
| | |
+-----------+-----------+ +----------------+-----+ +-----+----------------+
| FPGA (FPGA0_0) | | FPGA (FPGA1_0) | | FPGA (FPGA1_1) |
| ACCELERATOR_FPGA:1 | | ACCELERATOR_FPGA:1 | | ACCELERATOR_FPGA:1 |
| traits: | | traits: | | traits: |
| CUSTOM_TYPE1 | | CUSTOM_TYPE1 | | CUSTOM_TYPE2 |
+-----------------------+ +----------------------+ +----------------------+
To request FPGAs on the same NUMA node with VCPUs and MEMORY, a request may look like:
GET /allocation_candidates
?resources_COMPUTE=VCPU:1,MEMORY_MB:256
&resources_ACCEL=ACCELERATOR_FPGA:1
&group_policy=none
&same_subtree=_COMPUTE,_ACCEL
This will produce candidates including:
NUMA0(VCPU,MEMORY_MB) +FPGA0_0(ACCELERATOR_FPGA)NUMA1(VCPU,MEMORY_MB) +FPGA1_0(ACCELERATOR_FPGA)NUMA1(VCPU,MEMORY_MB) +FPGA1_1(ACCELERATOR_FPGA)
but not:
NUMA0(VCPU,MEMORY_MB) +FPGA1_0(ACCELERATOR_FPGA)NUMA0(VCPU,MEMORY_MB) +FPGA1_1(ACCELERATOR_FPGA)NUMA1(VCPU,MEMORY_MB) +FPGA0_0(ACCELERATOR_FPGA)
The request groups specified in the same_subtree need not have a
resources$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:
FPGA1_0(ACCELERATOR_FPGA) +FPGA1_1(ACCELERATOR_FPGA) +NUMA1
but not:
FPGA0_0(ACCELERATOR_FPGA) +FPGA1_1(ACCELERATOR_FPGA) +NUMA0FPGA0_0(ACCELERATOR_FPGA) +FPGA1_1(ACCELERATOR_FPGA) +NUMA1FPGA1_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.
