What error?

Debugging is probably the most difficult thing that I have to do every day.  Whether it’s something I’ve just written or a project done years ago, there is inevitably a failure somewhere.  Sometimes it’s due to changes in browsers or changes in settings on the server that cause the error, but sometimes the error has always been there, but just doesn’t have a solution.  I ran across one of those instances today. 

I have one interactive website that I’m quite proud of which has one error that shows up on occasion that I just can’t seem to solve.  The tricky part is, as soon as I get the handy dandy error message emailed to me, I go to the site to check it out, only to find no error.  What seems to be happening is that at some point a user is trying to make a payment on an invoice and for whatever reason, the calculation of the total of the invoice is trying to add in a null value, which causes an error.  When I go back in, there is no error.  Even within 5 minutes of the time when the error pops up, there is no error when I go to view the page.  Now it’s likely that something is being changed in the process, like a payment type or some other sort of change, but to me, that’s impossible to find, since I don’t have a record of it.  All I have is an email with an error message that this file is causing an error under these conditions.  I go back to meet those conditions and there is no error.  Frustrating. 

So once again, I have to dig back as far as possible into the code to figure out where the error is starting its path of destruction.  I actually love this part of my job, but what I don’t love is the time it takes to get there.