Debugging in 2012

This presentation was about Chronos, a proprietary Java debugger.  There is a free trial on their website.

While programs have advanced, debuggers haven't changed very much in the last 10-20 years.  Current debuggers:

• Assume flow is sequential
• Have a focus on single threads
• Designed for short running programs
• Not ideal for modern, multi-threaded, long running, or cloud applications

Logging is a broken technique for debugging:

• Tries to predict where the bug is in advance, and the prediction is usually wrong
• Messes up code

The future of debuggers? Chronon:

• Records entire execution of program for playback
• Recording is system, hardware, and platform independent
• Can record on 64-bit machine and replay on 32-bit or vice versa
• Can record on 12 core processor then replay on 2 cores
• Recordings can be shared
• Tester can record their session and result can be debugged by a developer
• How does it perform?
• Latest version, 3, is very optimised
• Intended for production environment
• Select what libraries need to be recorded; don't need to record Java API calls and state
• What can you do?
• Step forward and backwards in code
• See full state of the application at a given time
• Execution path of current method is highlighted, so you don't need to step through it to see what was called
• Bookmarks for jumping to parts of a recording
• Post-execution logging
• Go to line in run log and add logging statement separately from code
• Log messages can include state
• Timeline view
• See history of changes to a variable and method calls
• Filter based on values or line numbers
• Replay and see the logs
• Keeps log messages out of the code
• Exception log view
• Jump to where exception was thrown, and debug from there
• Limitations:
• External environment isn't available, so you can't make changes and see the results
• Need to ensure that code in workspace is the same as the recording being replayed

If you've ever had a bug that a tester found and you can't reproduce, Chronon might be the answer.  I've come across a few bugs like this, and I have one in particular which I might try to apply Chronos to.  I'm not sure what the licensing model is, but I think that the debugger itself might be free.