Re: Defensive Programming and Audit Trails

[dws]

Some very hard-to-debug breakage can happen when systems are deployed remotely, and the remote environment changes. To save yourself grief, provide a facility to

dump the environment into the log!

You have little control over when a customer might install the latest MS service pack, and service packs have a history of breaking things. Or, a customer might do a database upgrade, or an upgrade of some component you depend upon.

To defend against this, consider adding a logging option that will dump the following in to the log

• Checksums (or MD5 hashs) of your components
• The versions of all packages you depend on
• The versions (or sizes and timestamps) of all .DLLs or shared objects you depend on
• The OS version and patch level
• The database version (which you can usually query from the database after connecting)
• Available disk space
• Anything else that's appropriate for your application

Having this info in-hand can save hours of work, particularly when your support folks are dealing with a customer who is yelling loudly that your stuff is broken, and that nothing, nothing! on their end has changed.

And getting set up to record this info forces you to know your application at a deeper level, which can also be a win.