:orphan:
.. _ext-processes:

===============================
Running Custom Master Processes
===============================

.. note::
  :ref:`Salt engines <engines>` are a new feature in 2015.8.0 that let you run
  custom processes on the Salt master and on Salt minions. Salt engines provide
  more functionality than ``ext_processes`` by accepting arguments, and by
  providing access to Salt config, execution modules, and runners.

In addition to the processes that the Salt master automatically spawns,
it is possible to configure it to start additional custom processes.

This is useful if a dedicated process is needed that should run throughout
the life of the Salt master. For periodic independent tasks, a
:ref:`scheduled runner <scheduling-jobs>` may be more appropriate.

Processes started in this way will be restarted if they die and will be
killed when the Salt master is shut down.


Example Configuration
=====================

Processes are declared in the master config file with the `ext_processes`
option. Processes will be started in the order they are declared.

.. code-block:: yaml

    ext_processes:
      - mymodule.TestProcess
      - mymodule.AnotherProcess


Example Process Class
=====================

.. code-block:: python

    # Import python libs
    import time
    import logging
    from multiprocessing import Process

    # Import Salt libs
    from salt.utils.event import SaltEvent


    log = logging.getLogger(__name__)


    class TestProcess(Process):
        def __init__(self, opts):
            Process.__init__(self)
            self.opts = opts

        def run(self):
            self.event = SaltEvent('master', self.opts['sock_dir'])
            i = 0

            while True:
                self.event.fire_event({'iteration': i}, 'ext_processes/test{0}')
                time.sleep(60)
