Coordinated Exception Handling in Distributed Object Systems: from Model to System Implementation

Speaker: Jie Xu

Abstract

Exception handling in distributed and concurrent programs is a difficult task though it is often necessary. In many cases traditional exception mechanisms for sequential programs are no longer appropriate. One major difficulty is that the process of handling an exception may need to involve multiple concurrent components when they are cooperating in pursuit of a global goal. Another complication is that several exceptions may be raised concurrently in different nodes of a distributed environment. Existing proposals and actual concurrent languages either ignore these difficulties or only cope with a limited form of them. In this talk, I'll report major results of the three-year joint investigation of coordinated exception handling, conducted together with Alexander Romanovsky and Brian Randell. We attempt to provide a general solution, developed especially for distributed object systems, starting with from conceptual model, together with algorithmic mechanisms (and their correctness proofs) for coordinating concurrent components and resolving multiple exceptions, through to an actual system implementation. An industrial production cell is chosen as a case study to demonstrate the usefulness of the proposed model and algorithms. The supporting system and the resolution mechanism are implemented in distributed Ada 95 and examined through several performance-related experiments.