CernVM Co-Pilot: An extensible framework for building scalable computing infrastructures on the cloud

CernVM Co-Pilot is a framework for instantiating an ad-hoc computing infrastructure on top of managed or unmanaged computing resources. Co-Pilot can either be used to create a stand-alone computing infrastructure, or to integrate new computing resources into existing infrastructures (such as Grid or batch). Unlike traditional middleware systems, Co-Pilot components communicate using the Extensible Messaging and Presence protocol (XMPP). This allows the system to be easily scaled in case of a high load, and it also simplifies the development of new components. In this contribution we present the latest developments and the current status of the framework, discuss how it can be extended to suit the needs of a particular community, as well as describe the operational experience of using the framework in the LHC@home 2.0 volunteer computing project.