Automatic Deployment via git

Posted by Michael Reinsch on 2009-02-06

If you're using git to manage your homepage / blog / little web application, it is relatively easy to add automatic deployment functionality to simplify your work flow. Deploying a new version can then be a simple git push!

For this article, I'll use a Ruby on Rails application as the example. It should be easy enough to adapt this approach to other situations. You can even do more complex actions such as compiling a deployment archive as long as no manual intervention is required.

Let's assume you want to install your RoR application in /srv/web/my_app, and you have a bare git repository on the same server, in /srv/gitosis/repositories/my_app.git. All you need to do is create a clone from the repository in the deployment location, adjust the permissions of the log and tmp directories, configure the database connection if required and then you are done.

Applying updates with git in such an environment is already simple: develop and test on your local machine, eventually push your changes to the server and finally pull the changes into the deployment directory. For example:

client \$ git commit ...
client \$ git push
client \$ ssh server
server # cd /srv/web/my_app
server # git pull
server # touch tmp/restart.txt

This way, your local configuration is also protected by git and will be merged if possible (commit any local changes).

To further automate this, we can use the post-receive hook. In our example this is located at /srv/gitosis/repositories/my_app.git/hooks/post-receive. I have this hook call a script called update-rails.sh with the application name (my_app) as the parameter.

update-rails.sh looks like this:

#!/bin/sh
name=\$1
if [ -z "\$name" ] ; then
        echo "need to give name of checkout dir on command line"
        exit 1
fi

dir=/srv/web/\$name
if [ ! -d \$dir ] ; then
        echo "the directory \$dir does not exist"
        exit 1
fi

cd \$dir
env -i git pull
rake db:migrate
touch \$dir/tmp/restart.txt

As you can see, this script will also run any required DB migrations.

Simple, isn't it?