path: root/docs/userguide/feature.userguide.rst

.. This work is licensed under a Creative Commons Attribution 4.0 International License.
.. http://creativecommons.org/licenses/by/4.0

Promise description
===================
Promise is a resource reservation and management project to identify NFV related
requirements and realize resource reservation for future usage by capacity
management of resource pools regarding compute, network and storage.

The following are the key features provided by this module:

* Capacity Management
* Reservation Management
* Allocation Management

Promise capabilities and usage
==============================
The Colorado implementation of Promise is built with the YangForge data modeling
framework [#f2]_ , using a shim-layer on top of OpenStack to provide
the Promise features. This approach requires communication between
Consumers/Administrators and OpenStack to pass through the shim-layer. The
shim-layer intercepts the message flow to manage the allocation requests based
on existing reservations and available capacities in the providers. It also
extracts information from the intercepted messages in order to update its
internal databases. Furthermore, Promise provides additional intent-based APIs
to allow a Consumer or Administrator to perform capacity management (i.e. add
providers, update the capacity, and query the current capacity and utilization
of a provider), reservation management (i.e. create, update, cancel, query
reservations), and allocation management (i.e. create, destroy instances).

Detailed information about Promise use cases, features, interface
specifications, work flows, and the underlying Promise YANG schema can be found
in the Promise requirement document [#f1]_ .

Promise features and API usage guidelines and examples
------------------------------------------------------
This section lists the Promise features and API implemented in OPNFV Colorado.

Note: The listed parameters are optional unless explicitly marked as "mandatory".

Reservation management
^^^^^^^^^^^^^^^^^^^^^^
The reservation management allows a Consumer to request reservations for
resource capacity. Reservations can be for now or a later time window.
After the start time of a reservation has arrived, the Consumer can issue
create server instance requests against the reserved capacity. Note, a
reservation will expire after a predefined *expiry* time in case no
allocation referring to the reservation is requested.

The implemented workflow is well aligned with the described workflow in the
Promise requirement document [#f1]_ (Section 6.1) except for the
"multi-provider" scenario as described in :ref:`multi-provider` .

.. _create-reservation:

*create-reservation*
""""""""""""""""""""

This operation allows making a request to the reservation system to reserve
resources.

The operation takes the following input parameters:

* start: start time of the requested reservation
* end: end time of the requested reservation
* capacity.instances: amount of instances to be reserved
* capacity.cores: amount of cores to be reserved
* capacity.ram: amount of ram in MB to be reserved

Promise will check the available capacity in the given time window and in case
sufficient capacity exists to meet the reservation request, will mark those
resources "reserved" in its reservation map.

*update-reservation*
""""""""""""""""""""

This operation allows to update the reservation details for an existing
reservation.

It can take the same input parameters as in *create-reservation*
but in addition requires a mandatory reference to the *reservation-id* of the
reservation that shall be updated.

*cancel-reservation*
""""""""""""""""""""

This operation is used to cancel an existing reservation.

The operation takes the following input parameter:

* reservation-id (mandatory): identifier of the reservation to be canceled.

*query-reservation*
"""""""""""""""""""

The operation queries the reservation system to return reservation(s) matching
the specified query filter, e.g., reservations that are within a specified
start/end time window.

The operation takes the following input parameters to narrow down the query
results:

* without: excludes specified collection identifiers from the result
* elements.some: query for ResourceCollection(s) that contain some or more of these element(s)
* elements.every: query for ResourceCollection(s) that contain all of these element(s)
* window.start: matches entries that are within the specified start/
* window.end: end time window
* window.scope: if set to 'exclusive', only reservations with start AND end time
    within the time window are returned. Otherwise ('inclusive'), all
    reservation starting OR ending in the time windows are returned.
* show-utilization: boolean value that specifies whether to also return the
  resource utilization in the queried time window or not

Allocation management
^^^^^^^^^^^^^^^^^^^^^

*create-instance*
"""""""""""""""""

This operation is used to create an instance of specified resource(s) for
immediate use utilizing capacity from the pool. *Create-instance* requests can
be issued against an existing reservation, but also allocations without a
reference to an existing reservation are allowed. In case the allocation
request specifies a reservation identifier, Promise checks if a reservation
with that ID exists, the reservation start time has arrived (i.e. the
reservation is 'active'), and the required capacity for the requested flavor is
within the available capacity of the reservation. If those conditions are met,
Promise creates a record for the allocation (VMState="INITIALIZED") and update
its databases. If no *reservation_id* was provided in the allocation request,
Promise checks whether the required capacity to meet the request can be
provided from the available, non-reserved capacity. If yes, Promise creates a
record for the allocation with an unique *instance-id* and update its
databases. In any other case, Promise rejects the *create-instance* request.

In case the *create-instance* request is rejected, Promise responds with a
"status=rejected" providing the reason of the rejection. This will help the
Consumer to take appropriate actions, e.g., send an updated *create-instance*
request. In case the *create-instance* request was accepted and a related
allocation record has been created, the shim-layer issues a *createServer*
request to the VIM Controller (i.e. Nova) providing all information to create
the server instance.

The operation takes the following input parameters:

* name (mandatory): Assigned name for the instance to be created
* image (mandatory): the image to be booted in the new instance
* flavor (mandatory): the flavor of the requested server instance
* networks: the list of network uuids of the requested server instance
* provider-id: identifier of the provider where the instance shall be created
* reservation-id: identifier of a resource reservation the *create-instance*

The Colorado implementation of Promise has the following limitations:

* All create server instance requests shall pass through the Promise
  shim-layer such that Promise can keep track of all allocation requests. This
  is necessary as in the current release the sychronization between the VIM
  Controller and Promise on the available capacity is not yet implemented.
* *Create-allocation* requests are limited to "simple" allocations, i.e., the
  current workflow only supports the Nova compute service and
  *create-allocation* requests are limited to creating one server instance at a
  time
* Prioritization of reservations and allocations is yet not implemented.
  Future version may allow certain policy-based conflict resolution where,
  e.g., new allocation request with high priority can "forcefully" terminate
  lower priority allocations.


*destroy-instance*
""""""""""""""""""

This operation request to destroy an existing server instance and release it
back to the pool.

The operation takes the following input parameter:

* instance-id: identifier of the server instance to be destroyed

Capacity management
^^^^^^^^^^^^^^^^^^^
The capacity management feature allows the Consumer or Administrator to do
capacity planning, i.e. the capacity available to the reservation management
can differ from the actual capacity in the registered provider(s). This feature
can, e.g., be used to limit the available capacity for a given time window due
to a planned downtime of some of the resources, or increase the capacity
available to the reservation system in case of a planned upgrade of the
available capacity.

*increase/decrease-capacity*
""""""""""""""""""""""""""""

This operations allows to increase/decrease the total capacity that is made
available to the Promise reservation service between a specified window in
time. It does NOT increase the actual capacity of a given resource provider,
but is used for capacity management inside Promise.

This feature can be used in different ways, like

* Limit the capacity available to the reservation system to a value below 100%
  of the available capacity in the VIM, e.g., in order to leave "buffer" in the
  actual NFVI to be used outside the Promise reservation service.

* Inform the reservation system that, from a given time in the future,
  additional resources can be reserved, e.g., due to a planned upgrade of the
  available capacity of the provider.

* Similarily, the "decrease-capacity" can be used to reduce the consumable
  resources in a given time window, e.g., to prepare for a planned downtime of
  some of the resources.

* Expose multiple reservation service instances to different consumers sharing
  the same resource provider.

The operation takes the following input parameters:

* start: start time for the increased/decreased capacity
* end: end time for the increased/decreased capacity
* capacity.cores: Increased/decreased amount of cores
* capacity.ram: Increased/decreased amount of RAM
* capacity.instances: Increased/decreased amount of instances

Note, increase/decreasing the capacity in Promise is completely transparent to
the VIM. As such, when increasing the virtual capacity in Promise (e.g. for a
planned upgrade of the capacity), it is in the responsibility of the
Consumer/Administrator to ensure sufficient resources in the VIM are available
at the appropriate time, in order to prevent allocations against reservations
to fail due to a lack of resources. Therefore, this operations should only be
used carefully.


*query-capacity*
""""""""""""""""

This operation is used to query the available capacity information of the
specified resource collection. A filter attribute can be specified to narrow
down the query results.

The current implementation supports the following filter criteria:

* time window: returns reservations matching the specified window

* window scope: if set to 'exclusive', only reservations with start AND end time
  within the time window are returned. Otherwise, all reservation starting OR
  ending in the time windows are returned.

* metric: query for one of the following capacity metrics:

  * 'total': resource pools
  * 'reserved': reserved resources
  * 'usage': resource allocations
  * 'available': remaining capacity, i.e. neither reserved nor allocated

.. _multi-provider:

(Multi-)provider management
^^^^^^^^^^^^^^^^^^^^^^^^^^^

This API  towards OpenStack allows a Consumer/Administrator to add and remove
resource providers to Promise. Note, Promise supports a multi-provider
configuration, however, for Colorado, multi-provider support is not yet
fully supported.

*add-provider*
""""""""""""""

This operation is used to register a new resource provider into the Promise
reservation system.

Note, for Colorado, the add-provider operation should only be used to
register one provider with the Promise shim-layer. Further note that currently
only OpenStack is supported as a provider.

The operation takes the following input parameters:

* provider-type (mandatory) = 'openstack': select a specific resource provider
  type.
* endpoint (mandatory): target URL endpoint for the resource provider.
* username (mandatory)
* password (mandatory)
* region: specified region for the provider
* tenant.id: id of the OpenStack tenant/project
* tenant.name: name of the OpenStack tenant/project

.. [#f1] Promise requirement document,
         http://artifacts.opnfv.org/promise/docs/requirements/index.html

.. [#f2] YangForge framework, http://github.com/opnfv/yangforge