===========
Development
===========

Using a virtualenv
------------------

Although you don't strictly *have* to, you should use
`virtualenvwrapper <https://virtualenvwrapper.readthedocs.org/>`_ for isolating
your development environment.  It is to your benefit because you'll be able to
install the latest fedmsg from a git checkout without messing with your system
fedmsg install (if you have one).  The instructions here will assume you are
using that.

You can install it with::

    $ sudo yum install python-virtualenvwrapper

.. note:: If you decide not to use python-virtualenvwrapper, you can always use
   latest update of fedmsg in fedora.  If you are doing this, simply ignore all
   ``mkvirtualenv`` and ``workon`` commands in these instructions.  You can
   install fedmsg with ``sudo yum install fedmsg``.

Development Dependencies
------------------------

Get::

    $ sudo yum install python-virtualenv openssl-devel zeromq-devel gcc

Cloning the Upstream Git Repo
-----------------------------

The source code is on github.  For read-only access, simply::

    $ git clone git://github.com/fedora-infra/fedmsg.git

Of course, you may want to do the usual `fork and then clone
<https://help.github.com/articles/fork-a-repo>`_ pattern if you intend to
submit patches/pull-requests (please do!).

.. note::  If submitting patches, you should check :doc:`contributing` for
   style guidelines.

Setting up your virtualenv
--------------------------

Create a new, empty virtualenv and install all the dependencies from `pypi
<http://pypi.python.org>`_::

    $ cd fedmsg
    $ mkvirtualenv fedmsg
    (fedmsg)$ python setup.py develop

.. note::  If the mkvirtualenv command is unavailable try
   ``source /usr/bin/virtualenvwrapper.sh`` on Fedora (if you do not run Fedora
   you might have to adjust the command a little).

You should also run the tests, just to make sure everything is sane::

    (fedmsg)$ python setup.py test

Try out the shell commands
--------------------------

Having set up your environment in the `Hacking` section above, open up three
terminals.  In each of them, activate your virtualenv with::

  $ workon fedmsg

and in one, type::

  (fedmsg)$ fedmsg-relay

In the second, type::

  (fedmsg)$ fedmsg-tail --really-pretty

In the third, type::

  (fedmsg)$ echo "Hello, world" | fedmsg-logger

And you should see the message appear in the ``fedmsg-tail`` term.

Configuration
-------------

There is a folder in the root of the upstream git checkout named ``fedmsg.d/``.
:mod:`fedmsg.config` will try to read this whenever the fedmsg API is
invoked.  If you're starting a new project like a consumer or a webapp that is
sending fedmsg messages, you'll need to copy the ``fedmsg.d/`` directory to the
root directory of that project.  In :doc:`deployment`, that folder is kept in
``/etc/fedmsg.d/``.

.. note::  Watch out:  if you have a ``/etc/fedmsg.d/`` folder and a local
   ``./fedmsg.d/``, fedmsg will read both.  Global first, and then local.
   Local values will overwrite system-wide ones.

.. note::  The tutorial on `consuming FAS messages from stg
   <http://threebean.org/blog/fedmsg-tutorial-consuming-fas-stg>`_ might be of
   further help.  It was created before these instructions were written.
