Dodging Unsafe Update Points in Java Dynamic Software Updating Systems

Dynamic Software Updating (DSU) provides mechanisms to update a program without stopping its execution. An indiscriminate update, that does not consider the current state of the computation, potentially undermines the stability of the running application. To automatically determine a safe moment when to update the running system is still an open problem often neglected from the existing DSU systems. This paper proposes a mechanism to support the choice of a safe update point by marking which point can be considered unsafe and therefore dodged during the update. The method is based on decorating the code with some specific meta-data that can be used to find the right moment to do the update. The proposed approach has been implemented as an external component that can be plugged into every DSU system. The approach is demonstrated on the evolution of the HSQLDB system from two distinct versions to their next update.