Running out of file descriptors and eventual crash

Server generates errors and eventually crashes due to execeeding limit on number of open file descriptors.

This occurs when additional open_table_caches_instances are created. The calculation for open_files_limit does not account for the fact that there may be multiple instances.

I expect (but have not proven) problem could be avoided adjusting setting in config file to limit number of open_table_caches_instances or increasing open_files_limit. Currently neither of these are set in our config.