The catch is, we didn’t really want to force all our users to re-log into the app.  We could, and most probably wouldn’t notice, but that’s not how we roll.  So, we decided to migrate all the existing sessions from MySQL to Memcached.  Turns out it’s pretty easy.  MySQLSessionStore  keeps everything in a data column in the sessions table, which contains the base64-encoded output of Marshal.dump(<your session hash>).   The built-in logic in memcache-client handles the marshaling and unmarshaling when creating the new sessions, so migrating looks something like this on the console:

Simple, no? A word to the wise, though – do it in batches of 1000. Session.all would be bad.

“But my tests!” you cry.  “Surely the finely crafted specs I’ve been working on will save me!” The problem is that overly aggressive exception handling in your code will mask the true cause of errors, resulting in a false sense of security. Sure, assert_nothing_raised and should_not raise never fire: your code is consuming the warnings and continuing blithely on its way.

This is why most ActiveRecord reference material emphasizes the user of find (vs. find_by_id), save! and the like, but doesn’t include begin and rescue blocks – it’s often better to have things blow up on you than guess at what error conditions might arise and attempt to handle them as you’re writing the code.  You can write tests around the exceptions, insuring that your code errors out in the appropriate manner when faced with bad input or exceptional conditions.

On the other hand, when something unexpected happens in production and your site starts giving everyone an eyeful of  your funny 500 page you’re unlikely to be so happy with all those uncaught exceptions.  Ah, the usual tension between development and production.  Enter tattletale.

tattletale is your hall monitor, your prison snitch: it tattles on all the exceptions raised during a particular test run, including messages, backtrace and the test that raised it. All of your existing exception handlers will work as expected, so your code doesn’t change. I’ve written a Tattler for Test::Unit for starters; extending to your favorite test framework should be as easy as writing your own Tattler. Grab the gem off github and take back your exception handling.