What is file .asscache (tomcat 8)

I have a grails application that I deploy its’ war with tomcat 8.
Everything was working fine, and after a few weeks the website stoped working.
When I changed the server.xml to work with http connector instead of https it worked, but I need the ssl. What eventually solved the problem was adding a file C:\Program Files\Apache Software Foundation\Tomcat 8.0\build\.asscache and than restarting the machine.
After the restart the file was generated with text and the app returned to work. It’s the second time this happens to me (it seems that the file just disappeared after a while after the first time).
So my question is - Does anyone know that “.asscache” file? What does it do? I can’t find any information about it anywhere.
Thank you