A Lightweight, Static Approach to Detecting Unbounded Thread-Instantiation Loops

In server applications, threads are created to handle incoming requests. Since threads consume significant resources including CPU cycles and memory, it is important to control the number of threads that are created. In this paper, we introduce a lightweight, static approach to detecting unbounded thread- instantiation loops that may exist in a server application. The key observation of our approach is that threads are objects of special significance and the decision logic for thread instantiation is typically not complex. Our approach checks loops against some bounded thread-instantiation patterns. A loop is considered bounded if a pattern match is found. Otherwise, it is considered unbounded. Our approach is heuristic by nature. That is, it does not guarantee to detect all the unbounded loops and may report unbounded loops that are actually bounded. To evaluate the effectiveness of our approach, we report an Eclipse plugin called ThreadBoundChecker which implements our approach and an experiment on 24 real-life Java server applications. The results of our evaluation show that our approach can effectively detect unbounded thread-instantiation loops in these applications. In particular, 12 unbounded thread-instantiation loops detected by our approach are confirmed by the original developers.