Nondeterminism in ORBs: The Perception and the Reality

Nondeterminism is a source of problems for distributed replication because it makes it difficult to keep replicas consistent as they execute, process invocations and modify their internal states. Even if a middleware application is completely deterministic, the underlying middleware, e.g., the ORB, can continue to remain a source of nondeterminism. The paper presents our analysis of an open-source ORB from the viewpoint of nondeterminism. Our approach identifies the various sources of nondeterminism within the ORB. Our results demonstrate that while ORBs can contain several apparently nondeterministic system calls and functions, only a fraction of them manifest as actual nondeterminism and pose a threat to replica consistency