..
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      All Rights Reserved.

      Licensed under the Apache License, Version 2.0 (the "License"); you may
      not use this file except in compliance with the License. You may obtain
      a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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      License for the specific language governing permissions and limitations
      under the License.

===============================
Mistral workflow VIM monitoring
===============================

For the purpose to make tacker server scale, the mistral workflow is used to
re-implement the VIM monitoring feature.

The main monitoring process is like this:

- user registers a VIM
- tacker server saves it into database
- tacker server generates a mistral workflow and executes it
- the VIM monitor mistral action is executed and do the monitoring, if there
  is status change, it will RPC call conductor
- the conductor changes the VIM status


Feature exploration
===================

Firstly register a VIM:

.. code-block:: console

    $ tacker vim-register --config-file ~/testvim_config.yaml testvim2 -c id -c name -c status
    Created a new vim:
    +--------+--------------------------------------+
    | Field  | Value                                |
    +--------+--------------------------------------+
    | id     | 4406cf8f-f2af-46cc-bfb9-e00add5805b7 |
    | name   | testvim2                             |
    | status | PENDING                              |
    +--------+--------------------------------------+

..

The registered VIM's id is '4406cf8f-f2af-46cc-bfb9-e00add5805b7', after this,
there is a mistral workflow named as
'vim_id_4406cf8f-f2af-46cc-bfb9-e00add5805b7', is generated in mistral:

.. code-block:: console

    $ mistral workflow-list --filter name=vim_id_4406cf8f-f2af-46cc-bfb9-e00add5805b7 -c ID -c Name
    +--------------------------------------+---------------------------------------------+
    | ID                                   | Name                                        |
    +--------------------------------------+---------------------------------------------+
    | 0cd0deff-6132-4ee2-a181-1c877cd594cc | vim_id_4406cf8f-f2af-46cc-bfb9-e00add5805b7 |
    +--------------------------------------+---------------------------------------------+

..

and it is executed:

.. code-block:: console

    $ mistral execution-list --filter workflow_name=vim_id_4406cf8f-f2af-46cc-bfb9-e00add5805b7 -c ID -c 'Workflow name' -c State
    +--------------------------------------+---------------------------------------------+---------+
    | ID                                   | Workflow name                               | State   |
    +--------------------------------------+---------------------------------------------+---------+
    | 99ced0e2-be09-4219-ab94-299df8ee8789 | vim_id_4406cf8f-f2af-46cc-bfb9-e00add5805b7 | RUNNING |
    +--------------------------------------+---------------------------------------------+---------+

..

The monitoring task is running too:

.. code-block:: console

    $ mistral task-list --filter workflow_name=vim_id_4406cf8f-f2af-46cc-bfb9-e00add5805b7 -c ID -c 'Workflow name' -c Name  -c State
    +--------------------------------------+-----------------------------+---------------------------------------------+---------+
    | ID                                   | Name                        | Workflow name                               | State   |
    +--------------------------------------+-----------------------------+---------------------------------------------+---------+
    | f2fe2904-6ff2-4531-9bd0-4c998ef1515f | monitor_ping_vimPingVIMTASK | vim_id_4406cf8f-f2af-46cc-bfb9-e00add5805b7 | RUNNING |
    +--------------------------------------+-----------------------------+---------------------------------------------+---------+

..

Of course, the VIM's state is in 'REACHABLE' status:

.. code-block:: console

    $ tacker vim-list --name testvim2 -c id -c name -c status
    +--------------------------------------+----------+-----------+
    | id                                   | name     | status    |
    +--------------------------------------+----------+-----------+
    | 4406cf8f-f2af-46cc-bfb9-e00add5805b7 | testvim2 | REACHABLE |
    +--------------------------------------+----------+-----------+

..

The deletion of VIM will lead to removal of all of these mistral resources.


Rabbitmq queues
===============

Each mistral VIM monitoring action is listening on three queues:

.. code-block:: console

    ~/tacker$ sudo rabbitmqctl list_queues | grep -i KILL_ACTION
    KILL_ACTION    0
    KILL_ACTION.4406cf8f-f2af-46cc-bfb9-e00add5805b7    0
    KILL_ACTION_fanout_a8118e2e18b9443986a1b37f7b082ab9    0

..

But only KILL_ACTION with VIM id as suffix is used.