I fixed this problem by renaming the old history file
mv history.yml history
and then restarting the server. In my case thats
rackup -p 3030 -s puma
The history.yml file didn't reappear until after I stopped the server. I checked it with nano and it was full of data. Sorry I can't shed any light as to why it may have happened. Server details. Ubuntu 13.10 32bit Desktop