Using a virtualenv

Although you don’t strictly have to, you should use virtualenvwrapper 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 dnf install python-virtualenvwrapper


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 dnf install fedmsg.

Development Dependencies


$ sudo dnf install python-virtualenv libffi-devel openssl-devel \
  zeromq-devel gcc

Cloning the Upstream Git Repo

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

$ git clone git://

Of course, you may want to do the usual fork and then clone pattern if you intend to submit patches/pull-requests (please do!).


If submitting patches, you should check Contributing for style guidelines.

Setting up your virtualenv

Create a new, empty virtualenv and install all the dependencies from pypi:

$ cd fedmsg
$ mkvirtualenv fedmsg
(fedmsg)$ pip install -e .[all]


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


As discussed in the FAQ, M2Crypto requires the swig command to be available in order to build successfully. It’s recommended that you install M2Crypto using your system package manager, which can be done with dnf install m2crypto swig on Fedora.

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

(fedmsg)$ python 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.


There is a folder in the root of the upstream git checkout named fedmsg.d/. 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 Deploying fedmsg for yourself, that folder is kept in /etc/fedmsg.d/.


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.


The tutorial on consuming FAS messages from stg might be of further help. It was created before these instructions were written.