Adaptive Fault-Tolerant CORBA Components

Component-based software development allows developers to compose applications using software parts, called components. This approach represents an important step towards reducing development cost and time, and allows the creation of automated tools for software development. However, current applications have quality of service (QoS) requirements, and the existing component-based technologies provide limited support for QoS. In particular, fault tolerance is provided only in the form of persistence services, which enable the recovery of faulty components without loss of state information. This paper presents AFT-CCM (Adaptive Fault-Tolerance in the CORBA Component Model) – a model for building component-based applications with QoS requirements related to fault tolerance. AFT-CCM is based on CCM (CORBA Component Model), proposed by the OMG (Object Management Group), which extends the CORBA object model in order to introduce a new abstraction – the component. The AFT-CCM model allows the application user to specify QoS requirements that will be interpreted in order to adapt the configuration of replicated components. Characteristics such as the number of replicas and the replication technique will be defined aiming to fulfill the fault tolerance requirements specified by the user. This process is accomplished at execution time employing a set of CCM components that deal with the non-functional aspects of the application. The characteristics of this model, a prototype implementation, and an analysis of its functionality in the face of other proposals found in the literature are described along this paper.