.. _variables:

##########
Variables
##########



In this chapter you are going to learn what are variables in Orchestra Manager and how to use them.



What is variable
================

Orchestra Manager's Variables are a very powerful tool that helps you to manage a lot of settings and parameters within devices, compositions and fleets in Orchestra Manager. They are easily manageable, as they use a straightforward approach: there are 4 levels of variables Global, Composition, Fleet and Device, they are overriding each other respectively.

How do they override each other
===============================

Variables follow one simple rule: **the most specific level wins.**
Orchestra checks four levels, from broadest to most specific:
Global → Composition → Fleet → Device.

**Example:** the ``UPDATE`` variable controls how often devices send you updates.

.. list-table::
   :header-rows: 1
   :widths: 20 20 60

   * - Level
     - Value
     - Who ends up with this value
   * - Global
     - ``UPDATE=24h``
     - All devices that no other level covers
   * - Composition
     - ``UPDATE=16h``
     - Devices running this composition, outside the fleet below
   * - Fleet
     - ``UPDATE=12h``
     - Devices in this fleet, except the specific device
   * - Device
     - ``UPDATE=1h``
     - Only the specific device

In short: each level overrides the one above it, so the test device
reports every hour even though the global value is 24 hours.

Create a Global variable
=========================

.. note:: In order to check how to can create variables on other levels, check Composition, Fleet or Device chapters

In order to create a variable you should go to the variables tab

.. image:: images/vr-variables-in-sidebar.png
   :alt: Where to find Variables in sidebar
   :align: center
   :height: 500px


Find a **\"+\"** button in the Variables page

.. image:: images/vr-create-button.png
   :alt: Where to find create new variable button
   :align: center
   :width: 300px


Specify variable's Key, choose the type of value (text or file) and provide a it. After that, add a description. *Note that descriptions are optional, but we recommend to provide variables with a clear description*. At the end you will have something like this: 

.. image:: images/vr-creating-variable.png
   :alt: Example creation of a variable
   :align: center
   :width: 300px

Changing and Deleting a Variable
=================================

In order to change or delete variable you simply need to click it in the list of variables. You will see this pop up: 

.. image:: images/vr-change-delete.png
   :alt: Example creation of a variable
   :align: center
   :width: 300px

To delete the variable simply click **Delete variable** button.

If you want to change the name, value or description, everything that you need to do is change the value in the fields you want to be changed. After that press **Save** button.

.. note:: A new variable value reaches devices only after you restart the release