.. _decompose_services:

======================================
Decompose the controller node services
======================================

You can run different services on dedicated OpenStack nodes depending on
needs of your OpenStack environment. Using the Fuel CLI you can move
controller node services out of the existing controller role into
custom roles and assign these roles to dedicated nodes. This capability
may be helpful while managing highly-loaded OpenStack environments.

The services available for decomposition are:

* Neutron (including L3 agents, LBaaS, and others)
* Keystone
* MySQL DB
* RabbitMQ

**To decompose the controller node services:**

#. Log in to the Fuel Master node console.
#. Download the controller's role configuration:

   .. code-block:: console

      fuel role --release 2 --role controller --file controller.yaml

   You will get the configuration file with the following content:

   .. code-block:: yaml

      name: controller
      meta:
        conflicts:
          - compute
        description: >
          The Controller initiates orchestration activities and provides an
          external API.  Other components like Glance (image storage), Keystone
          (identity management), Horizon (OpenStack dashboard) and Nova-Scheduler
          are installed on the controller as well.
        group: base
        has_primary: true
        limits:
          min: 1
          overrides:
            - condition: settings:neutron_advanced_configuration.neutron_l3_ha.value == true
              message: >
                Neutron L3 HA requires at least 2 Controller nodes to function
                properly.
              min: 2
          recommended: 3
        name: Controller
        public_for_dvr_required: true
        public_ip_required: true
        tags:
          - controller
          - rabbitmq
          - database
          - keystone
          - neutron
        update_required:
          - compute
          - cinder
        weight: 10
      volumes_roles_mapping:
        - allocate_size: min
          id: os
        - allocate_size: min
          id: logs
        - allocate_size: all
          id: image
        - allocate_size: min
          id: mysql
        - allocate_size: min
          id: horizon

#. In ``controller.yaml``, remove the tag from the ``tags`` section that
   corresponds to the service you need to move to a dedicated node and save
   the changes.

   For example, remove the ``database`` tag and save the changes. Now, your
   controller role configuration file does not include the ``database`` tag
   in the ``tags`` section, and the ``mysql`` record in
   the ``volumes_roles_mapping`` section:

   .. code-block:: yaml
      :emphasize-lines: 24-28, 33-41

      name: controller
      meta:
        conflicts:
          - compute
        description: >
          The Controller initiates orchestration activities and provides an
          external API.  Other components like Glance (image storage), Keystone
          (identity management), Horizon (OpenStack dashboard) and Nova-Scheduler
          are installed on the controller as well.
        group: base
        has_primary: true
        limits:
          min: 1
          overrides:
            - condition: settings:neutron_advanced_configuration.neutron_l3_ha.value == true
              message: >
                Neutron L3 HA requires at least 2 Controller nodes to function
                properly.
              min: 2
          recommended: 3
        name: Controller
        public_for_dvr_required: true
        public_ip_required: true
        tags:
          - controller
          - rabbitmq
          - keystone
          - neutron
        update_required:
          - compute
          - cinder
              weight: 10
      volumes_roles_mapping:
        - allocate_size: min
          id: os
        - allocate_size: min
          id: logs
        - allocate_size: all
          id: image
        - allocate_size: min
          id: horizon

#. Upload the updated controller role:

   .. code-block:: console

      fuel role --release 2 --role controller --update --file controller.yaml

#. Create a new custom role for the service you need to remove from
   the controller node:

   #. For example, create and edit ``database.yaml`` specifying the removed
      entries from the controller role configuration:

      .. code-block:: yaml

         name: database
         meta:
           name: Database
           description: >
             Separated DB from controller.
           group: base
           conflicts:
             - controller
             - compute
           has_primary: true
           limits:
             min: 1
           update_required:
             - controller
             - database
           tags:
             - database
           weight: 100
         volumes_roles_mapping:
           - allocate_size: min
             id: os
           - allocate_size: min
             id: mysql

   #. In the Fuel CLI, create the new role based on the ``database.yaml``
      configuration file:

      .. code-block:: console

         fuel role --release 2 --create --file database.yaml

#. Assign the newly created role using the Fuel web UI or CLI as described
   in :ref:`change-roles`.

#. To apply the changes, deploy your OpenStack environment.

.. seealso::

   * :ref:`cli-roles`