Have you tried use DBI_TRACE or putting in a warn statement to see if the disconnect() really gets called? Maybe the ping above it is failing and causing it to get skipped.

Incidentally, your connect_db() sub will always sleep for at least 1 second, even if it connects right away. That's probably not what you want.

Ultimately, I recommend you get rid of this code and use $dbh->connect_cached() instead. It is similar to Apache::DBI, but doesn't prevent disconnects.