Monitoring tools will record the result of what happened to your web application or system when a problem arises, but for some classes of problem are of limited help in working out what happened, except through inference or by way of anecdotal evidence.

This talk will describe the limitations on what monitoring tools can help you with. It will then move onto look at a range of debugging tools and techniques which can be applied to web applications, but also separate them into what can and cannot be used on live production web applications.

Topics which will be discussed will include:

* Browser viewable error pages.
* Browser based debuggers.
* Python interactive debuggers.
* Post-mortem exception analysis.
* Methods for dumping Python stack traces
* Methods for dumping C stack traces.
* Methods for analysing thread utilisation.
* Interactive process introspection tools.
* Error reporting and logging services.
* Performance monitoring services.