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Abstract |
Back-in-time debuggers offer an interactive exploration interface to execution traces. However, maintaining a good level of inter- activity with large execution traces is challenging. Current approaches either maintain execution traces in memory, which limits scalability, or perform exhaustive on-disk indexing, which is not efficient enough. We present a novel scalable disk-based approach that supports efficient capture, indexing, and interactive navigation of arbitrarily large execution traces. In particular, our approach provides strong guarantees in terms of query processing time, ensuring an interactive debugging experience. The execution trace is divided into bounded-size execution blocks about which summary information is indexed. Blocks themselves are discarded, and retrieved as needed through partial deterministic replay. For querying, the index provides coarse answers at the level of execution blocks, which are then replayed to find the exact answer. Benchmarks on a prototype for Java show that the system is fast in practice, and outperforms existing back-in-time debuggers. |
