Systems Group Master’s Thesis The Virtual OSGi Framework

ii OSGi (Open Service Gateway Initiative) is an open industry standard. The OSGi specifications describe a dynamic module system for Java. It is a plat-form for managing Java software modules, which are called bundles. Bundles can be combined to form larger applications. An important aspect of the OSGi framework is the management of the dependencies between bundles. The OSGi framework was intented to operate on a machine. Recently, different approaches have emerged which are trying to facilitate remote access to services through bridging between the otherwise isolated framework instances. The disadvan-tages of the bridging approach is that it does not provide a unified access to local and remote services and it does not provide dynamism. Achieving this would unavoidably mean altering the framework implementation. However, the middleware should not impose any restrictions on OSGi services. In particular, it should be possible to use existing bundles and services in distributed setups without any need for modification. This thesis presents the Virtual OSGi framework, a distributed OSGi frame-work implementation, which is able to transparently run on multiple machines, yet acting like a single OSGi framework. The Virtual OSGi framework does so by adding a virtualization layer on top of each individual OSGi runtime. The underlying infrastructure of the system is a peer to peer network based on a distributed hash table. Beside maintaining non-invasiveness, other challenges that needed to be dealt with, were the connection and communication of dif-ferent OSGi frameworks, which are spread across the system. Furthermore, the treatment of bundles and their lifecycle. Finally, for the treatment of remote services, their registration and how an application will call them, the Virtual OSGi Framework makes the contribution of unifying local and remote services, without posing any restriction to the services that are registered in the frame-work. Finally, in this thesis, we compare the Virtual OSGi framework with other distributed systems, and we discuss what are its advantages and disadvantages of the Virtual OSGi approach. i