.. _getting_started_daemon:


Daemon Configuration
====================

While servers, often referred to as daemons in the PyroLab docs, and services
registered through them can be thought about and developed separately, in
deployment, their configurations are linked. Hence this section will again
reference services, in addition to servers.

Server daemons and service configurations are only important for host machines
providing services to a PyroLab network. For a client simply connecting to the
network to utilize available PyroLab services, there is no need to configure
servers or services.

Let's take a look at the server configuration class,
:py:class:`~pyrolab.configure.DaemonConfiguration`.

----

.. autoclass:: pyrolab.configure.DaemonConfiguration
   :members: __init__
   :noindex:

----

First, notice that all the configuration values have "sensible" defaults.
PyroLab by default keeps everything on localhost for security's sake---you 
don't want to unwittingly open up your ports to the world. You have to 
explicitly tell PyroLab to do that.

Second, notice that in a YAML representation of the nameserver's configuration, 
only the keys that are different from the defaults need to be defined; the
model that loads the file will automatically populate the missing fields with
the default values.

We can work with DaemonConfiguration objects either through a text YAML file,
or by constructing the actual Python object. For now, we'll use Python
directly:

.. code-block:: python
   :caption: The default server configuration, interacting directly with 
      the Python object.

   >>> from pyrolab.configure import DaemonConfiguration
   >>> config = DaemonConfiguration()
   >>> config.module, config.classname, config.host, config.port
   ('pyrolab.daemon', 'Daemon', 'localhost', 0)

.. code-block:: python
   :caption: Server configuration, interacting with the Python object, with
      values modified from the default.

   >>> from pyrolab.configure import DaemonConfiguration
   >>> config = DaemonConfiguration(classname="LockableDaemon", host="public", port=2022)
   >>> config.module, config.classname, config.host, config.port
   ('pyrolab.daemon', 'LockableDaemon', 'public', 2022)

These objects have a :py:func:`~pyrolab.configure.YAMLMixin.yaml` method that
can be used to dump the configuration to a YAML file. It accepts a parameter
that allows you to dump only the values that differ from the default:

.. code-block:: python
   :caption: The default server configuration, interacting with the YAML
      representation.

   >>> from pyrolab.configure import DaemonConfiguration
   >>> config = DaemonConfiguration()
   >>> print(config.yaml())
   module: pyrolab.server
   classname: Daemon
   host: localhost
   port: 0
   unixsocket: null
   nathost: null
   natport: 0
   servertype: thread

.. code-block:: python
   :caption: Modified server configuration, interacting with the YAML 
      representation, with defaults excluded.

   >>> from pyrolab.configure import DaemonConfiguration
   >>> config = DaemonConfiguration(classname="LockableDaemon", host="public", port=2022)
   >>> print(config.yaml(exclude_defaults=True))
   classname: LockableDaemon
   host: public
   port: 2022