The OpenStack example

The Puppet OpenStack modules (search Puppet at http://github.com/openstack, formerly hosted in http://github.com/stackforge), are probably the largest and most remarkable example of how Puppet is used to manage a complex set of applications that have to be interconnected and configured accordingly.

Component (application) modules

There are different modules for each OpenStack component (such as Nova, Glance, Horizon, Cinder, Ceilometer, Keystone, Swift or Quantum/Neutron). They can be retrieved from https://github.com/openstack/puppet-<component>, so, for example, Nova's module can be found at https://github.com/openstack/puppet-nova.

These modules manage all the different configurations via a settings-based approach, with native types that set the single lines of each configuration file (which may be more than one for each component) and with different subclasses that expose all the parameters needed to manage different services or features of each component...