DMTCP: Bringing Checkpoint-Restart to Python

DMTCP (Distributed MultiThreaded CheckPointing) is a mature checkpoint-restart package. It operates in user-space without kernel privilege, and adapts to application-specific requirements through plugins. While DMTCP has been able to checkpoint Python and IPython "from the outside" for many years, a Python module has recently been created to support DMTCP. IPython support is included through a new DMTCP plugin. A checkpoint can be requested interactively within a Python session, or under the control of a specific Python program. Further, the Python program can execute specific Python code prior to checkpoint, upon resuming (within the original process), and upon restarting (from a checkpoint image). Applications of DMTCP are demonstrated for: (i) Python-based graphics using VNC; (ii) a Fast/Slow technique to use multiple hosts or cores to check one Cython computation in parallel; and (iii) a reversible debugger, FReD, with a novel reverse-expression watchpoint feature for locating the cause of a bug.