.. This work is licensed under a Creative Commons Attribution 4.0 International License.
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Doctor capabilities and usage
=============================

:numref:`figure1` shows the currently implemented and tested architecture of
Doctor. The implementation is based on OpenStack and related components. The
Monitor can be realized by a sample Python-based implementation provided in the
Doctor code repository. The Controller is realized by OpenStack Nova, Neutron
and Cinder for compute, network and storage, respectively. The Inspector can be
realized by OpenStack Congress or a sample Python-based implementation also
available in the code repository of Doctor. The Notifier is realized by
OpenStack Aodh.

.. figure:: images/figure1.png
   :name: figure1
   :width: 100%

   Implemented and tested architecture


Immediate Notification
----------------------

Immediate notification can be used by creating 'event' type alarm via
OpenStack Alarming (Aodh) API with relevant internal components support.

See, upstream spec document:
http://specs.openstack.org/openstack/ceilometer-specs/specs/liberty/event-alarm-evaluator.html

An example of a consumer of this notification can be found in the Doctor
repository. It can be executed as follows:

.. code-block:: bash

    git clone https://gerrit.opnfv.org/gerrit/doctor -b stable/danube
    cd doctor/tests
    CONSUMER_PORT=12346
    python consumer.py "$CONSUMER_PORT" > consumer.log 2>&1 &

Consistent resource state awareness
-----------------------------------

Resource state of compute host can be changed/updated according to a trigger
from a monitor running outside of OpenStack Compute (Nova) by using
force-down API.

See
http://artifacts.opnfv.org/doctor/danube/manuals/mark-host-down_manual.html
for more detail.

Valid compute host status given to VM owner
-------------------------------------------

The resource state of a compute host can be retrieved by a user with the
OpenStack Compute (Nova) servers API.

See
http://artifacts.opnfv.org/doctor/danube/manuals/get-valid-server-state.html
for more detail.