.. Copyright 2014 tsuru authors. All rights reserved.
   Use of this source code is governed by a BSD-style
   license that can be found in the LICENSE file.

Unit states
===========

The unit status is the way to know what is happening with a unit. You can use the
`tsuru app info -a <appname>` to see the unit status:

.. highlight:: bash

::

    $ tsuru app info -a tsuru-dashboard
    Application: tsuru-dashboard
    Platform: python
    ...
    Units: 1
    +---------------------------------------+-------+
    | Unit                                  | State |
    +------------------------------------- -+-------+
    | tsuru-dashboard-web-9cf863c2c1-63c2c1 | ready |
    +---------------------------------------+-------+

The unit state flow is:

.. highlight:: bash

::

    +----------+                           start          +---------+
    | building |                   +---------------------+| stopped |
    +----------+                   |                      +---------+
          ^                        |                           ^
          |                        |                           |
       deploy                      |                         stop
          |                        |                           |
          +       assigned         v                           +
     +---------+  to node    +----------+                 +---------+  healthcheck ok   +-------+
     | created | +---------> | starting | +-------------> | started | +---------------> | ready |
     +---------+             +----------+                 +---------+                   +-------+
                                   +                         ^ +
                                   |                         | |
                                   |                         | |
                                   |                         | |
                                   v                         | |
                               +-------+                     | |
                               | error | +-------------------+ |
                               +-------+ <---------------------+

* `created`: is the initial status of an unit.
* `building`: is the status for units being provisioned by the provisioner, like during deployment.
* `error`: is the status for units that failed to start, because of an application error.
* `starting`: is set when the container is started in docker.
* `started`: is for cases where the unit is up and running.
* `ready`: is for cases where the unit is up and running and healthcheck is working.
* `stopped`: is for cases where the unit has been stopped.