Cyclic Distributed Garbage Collection Without Global Synchronization in CORBA

1 Abstract This paper describes an algorithm for cyclic distributed garbage collection and its implementation. The algorithm is an extension of reference-listing that collects cyclic garbage. It uses back-tracing instead of mark-and-sweep to eliminate the need of global synchronization. First, by using a special heuristic the algorithm chooses an object that is likely to be garbage (suspect). Then the algorithm recursively traces back the references to nd the transitive closure of objects that reach the suspect. If this closure does not contain any root, the objects in the closure are garbage, and therefore collected. Back-tracing distributed garbage collection has been covered in previous works, however none of these works mentioned the issues involved in the implementation of this algorithm in a real environment. These implementation issues are addressed and solved in this paper. To prove the feasibility of back-tracing, it has been implemented using oo the shelf software components. This paper describes the algorithm, the issues, their solutions and an implementation. 2 Introduction The way networking applications are implemented has evolved since the creation of the In-ternet. The growth in complexity of these applications has motivated the creation of better networking abstractions to deal with this complexity. This evolution is similar to the evolution of computer languages. Garbage collection is now a required feature in modern computer languages. For the same reasons, distributed garbage collection is also a necessity in modern distributed systems. Distributed garbage collection algorithms can be grouped in two families: Reference Counting and TracinggJon96, PS95].