Merge "Update docs structure according to new guidelines in https://wiki.opnfv.org/display/DOC"

1 files changed, 313 insertions, 0 deletions

diff --git a/docs/development/requirements/impl_architecture.rst b/docs/development/requirements/impl_architecture.rst
new file mode 100644
index 0000000..d7375d5
--- /dev/null
+++ b/docs/development/requirements/impl_architecture.rst
@@ -0,0 +1,313 @@
+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+Detailed architecture and message flows
+=======================================
+
+Within the Promise project we consider two different architectural options, i.e.
+a *shim-layer* based architecture and an architecture targeting at full
+OpenStack *integration*.
+
+Shim-layer architecture
+-----------------------
+
+The *shim-layer architecture* is using a layer on top of OpenStack to provide
+the capacity management, resource reservation, and resource allocation features.
+
+
+Detailed Message Flows
+^^^^^^^^^^^^^^^^^^^^^^
+
+Note, that only selected parameters for the messages are shown. Refer to
+:ref:`northbound_API` and Annex :ref:`yang_schema` for a full set of message
+parameters.
+
+Resource Capacity Management
+""""""""""""""""""""""""""""
+
+.. figure:: images/figure5_new.png
+    :name: figure5
+    :width: 90%
+
+    Capacity Management Scenario
+
+:numref:`figure5` shows a detailed message flow between the consumers and the
+capacity management functional blocks inside the shim-layer. It has the
+following steps:
+
+    * Step 1a: The Consumer sends a *query-capacity* request to Promise
+      using some filter like time-windows or resource type. The capacity is
+      looked up in the shim-layer capacity map.
+
+    * Step 1b: The shim-layer will respond with information about the
+      total, available, reserved, and used (allocated) capacities matching the
+      filter.
+
+    * Step 2a: The Consumer can send *increase/decrease-capacity* requests
+      to update the capacity available to the reservation system. It can be
+      100% of available capacity in the given provider/source or only a subset,
+      i.e., it can allow for leaving some "buffer" in the actual NFVI to be
+      used outside the Promise shim-layer or for a different reservation
+      service instance. It can also be used to inform the reservation system
+      that from a certain time in the future, additional resources can be
+      reserved (e.g. due to a planned upgrade of the capacity), or the
+      available capacity will be reduced (e.g. due to a planned downtime of
+      some of the resources).
+
+    * Step 2b: The shim-layer will respond with an ACK/NACK message.
+
+    * Step 3a: Consumers can subscribe for capacity-change events using a
+      filter.
+
+    * Step 3b: Each successful subscription is responded with a
+      subscription_id.
+
+    * Step 4: The shim-layer monitors the capacity information for the
+      various types of resources by periodically querying the various
+      Controllers (e.g. Nova, Neutron, Cinder) or by creating event alarms in
+      the VIM (e.g. with Ceilometer for OpenStack) and updates capacity
+      information in its capacity map.
+
+    * Step 5: Capacity changes are notified to the Consumer.
+
+Resource Reservation
+""""""""""""""""""""
+
+.. figure:: images/figure6_new.png
+    :name: figure6
+    :width: 90%
+
+    Resource Reservation for Future Use Scenario
+
+:numref:`figure6` shows a detailed message flow between the Consumer and the
+resource reservation functional blocks inside the shim-layer. It has the
+following steps:
+
+    * Step 1a: The Consumer creates a resource reservation request for
+      future use by setting a start and end time for the reservation as well as
+      more detailed information about the resources to be reserved. The Promise
+      shim-layer will check the free 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.
+
+    * Step 1b: If the reservation was successful, a reservation_id and
+      status of the reservation will be returned to the Consumer. In case the
+      reservation cannot be met, the shim-layer may return information about
+      the maximum capacity that could be reserved during the requested time
+      window and/or a potential time window where the requested (amount of)
+      resources would be available.
+
+    * Step 2a: Reservations can be updated using an *update-reservation*,
+      providing the reservation_id and the new reservation_data. Promise
+      Reservation Manageer will check the feasibility to update the reservation
+      as requested.
+
+    * Step 2b: If the reservation was updated successfully, a
+      reservation_id and status of the reservation will be returned to the
+      Consumer. Otherwise, an appropriate error message will be returned.
+
+    * Step 3a: A *cancel-reservation* request can be used to withdraw an
+      existing reservation. Promise will update the reservation map by removing
+      the reservation as well as the capacity map by adding the freed capacity.
+
+    * Step 3b: The response message confirms the cancelation.
+
+    * Step 4a: Consumers can also issue *query-reservation* requests to
+      receive a list of reservation. An input filter can be used to narrow down
+      the query, e.g., only provide reservations in a given time window.
+      Promise will query its reservation map to identify reservations matching
+      the input filter.
+
+    * Step 4b: The response message contains information about all
+      reservations matching the input filter. It also provides information
+      about the utilization in the requested time window.
+
+    * Step 5a: Consumers can subscribe for reservation-change events using
+      a filter.
+
+    * Step 5b: Each successful subscription is responded with a
+      subscription_id.
+
+    * Step 6a: Promise synchronizes the available and used capacity with
+      the underlying VIM.
+
+    * Step 6b: In certain cases, e.g., due a failure in the underlying
+      hardware, some reservations cannot be kept up anymore and have to be
+      updated or canceled. The shim-layer will identify affected reservations
+      among its reservation records.
+
+    * Step 7: Subscribed Consumers will be informed about the updated
+      reservations. The notification contains the updated reservation_data and
+      new status of the reservation. It is then up to the Consumer to take
+      appropriate actions in order to ensure high priority reservations are
+      favored over lower priority reservations.
+
+Resource Allocation
+"""""""""""""""""""
+
+.. figure:: images/figure7_new.png
+    :name: figure7
+    :width: 90%
+
+    Resource Allocation
+
+:numref:`figure7` shows a detailed message flow between the Consumer, the
+functional blocks inside the shim-layer, and the VIM. It has the following
+steps:
+
+    * Step 1a: The Consumer sends a *create-instance* request providing
+      information about the resources to be reserved, i.e., provider_id
+      (optional in case of only one provider), name of the instance, the
+      requested flavour and image, etc. If the allocation is against an
+      existing reservation, the reservation_id has to be provided.
+
+    * Step 1b: If a reservation_id was provided, 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 and update its databases. In any other case, Promise rejects
+      the *create-instance* request.
+
+    * Step 2: In the case the *create-instance* request was 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. The allocation work flow will
+      terminate at this step and the below steps are not executed.
+
+    * Step 3a: If 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 providing all information to
+      create the server instance.
+
+    * Step 3b: The VIM Controller sends an immediate reply with an
+      instance_id and starts the VIM-internal allocation process.
+
+    * Step 4: The Consumer gets an immediate response message with
+      allocation status "in progress" and the assigned instance_id.
+
+    * Step 5a+b: The consumer subscribes to receive notifications about
+      allocation events related to the requested instance. Promise responds
+      with an acknowledgment including a subscribe_id.
+
+    * Step 6: In parallel to the previous step, Promise shim-layer creates
+      an alarm in Aodh to receive notifications about all changes to the
+      VMState for instance_id.
+
+    * Step 7a: The VIM Controller notifies all instance related events to
+      Ceilometer. After the allocation has been completed or failed, it sends
+      an event to Ceilometer. This triggers the OpenStack alarming service Aodh
+      to notify the new VMState (e.g. ACTIVE and ERROR) to the shim-layer that
+      updates its internal allocation records.
+
+    * Step 7b: Promise sends a notification message to the subscribed
+      Consumer with information on the allocated resources including their new
+      VMState.
+
+    * Step 8a+b: Allocated instances can be terminated by the Consumer by
+      sending a *destroy-instance* request to the shim-layer. Promise responds
+      with an acknowledgment and the new status "DELETING" for the instance.
+
+    * Step 9a: Promise sends a *deleteServer* request for the instance_id
+      to the VIM Controller.
+
+    * Step 10a: After the instance has been deleted, an event alarm is
+      sent to the shim-layer that updates its internal allocation records and
+      capacity utilization.
+
+    * Step 10b: The shim-layer also notifies the subscribed Consumer about
+      the successfully destroyed instance.
+
+
+Internal operations
+^^^^^^^^^^^^^^^^^^^
+
+.. note:: This section is to be updated
+
+In the following, the internal logic and operations of the shim-layer will be
+explained in more detail, e.g. the "check request" (step 1b in
+:numref:`figure7` of the allocation work flow).
+
+
+
+Integrated architecture
+-----------------------
+
+The *integrated architecture* aims at full integration with OpenStack.
+This means that it is planned to use the already existing OpenStack APIs
+extended with the reservation capabilities.
+
+The advantage of this approach is that we don't need to re-model the
+complex resource structure we have for the virtual machines and the
+corresponding infrastructure.
+
+The atomic item is the virtual machine with the minimum set of resources
+it requires to be able to start it up. It is important to state that
+resource reservation is handled on VM instance level as opposed to standalone
+resources like CPU, memory and so forth. As the placement is an important
+aspect in order to be able to use the reserved resources it provides the
+constraint to handle resources in groups.
+
+The placement constraint also makes it impossible to use a quota management
+system to solve the base use case described earlier in this document.
+
+OpenStack had a project called Blazar, which was created in order to provide
+resource reservation functionality in cloud environments. It uses the Shelve
+API of Nova, which provides a sub-optimal solution. Due to the fact that this
+feature blocks the reserved resources this solution cannot be considered to
+be final. Further work is needed to reach a more optimal stage, where the
+Nova scheduler is intended to be used to schedule the resources for future
+use to make the reservations.
+
+Phases of the work
+^^^^^^^^^^^^^^^^^^
+
+The work has two main stages to reach the final solution. The following main work items
+are on the roadmap for this approach:
+
+#. Sub-optimal solution by using the shelve API of Nova through the Blazar project:
+
+   * Fix the code base of the Blazar project:
+
+     Due to integration difficulties the Blazar project got suspended. Since the last
+     activities in that repository the OpenStack code base and environment changed
+     significantly, which means that the project's code base needs to be updated to the
+     latest standards and has to be able to interact with the latest version of the
+     other OpenStack services.
+
+   * Update the Blazar API:
+
+     The REST API needs to be extended to contain the attributes for the reservation
+     defined in this document. This activity shall include testing towards the new API.
+
+#. Use Nova scheduler to avoid blocking the reserved resources:
+
+   * Analyze the Nova scheduler:
+
+     The status and the possible interface between the resource reservation system and
+     the Nova scheduler needs to be identified. It is crucial to achieve a much more
+     optimal solution than what the current version of Blazar can provide. The goal is
+     to be able to use the reserved resources before the reservation starts. In order to
+     be able to achieve this we need the scheduler to do scheduling for the future
+     considering the reservation intervals that are specified in the request.
+
+   * Define a new design based on the analysis and start the work on it:
+
+     The design for the more optimal solution can be defined only after analyzing the
+     structure and capabilities of the Nova scheduler.
+
+   * This phase can be started in parallel with the previous one.
+
+Detailed Message Flows
+^^^^^^^^^^^^^^^^^^^^^^
+
+.. note:: to be done
+
+Resource Reservation
+""""""""""""""""""""
+
+.. note:: to be specified