title: micrometer prometheus : add custom host metrics?
body: <p>I am using micrometer and prometheus into a spring boot 2 application : everything works like a charm.
  However i recently had an 'infra issue': my application generated 'too many open files'</p>
  
  <p>The prometheus endpoint returns the process_open_files (the files opened by my spring application) and the process_files_max_files which is the max open files allowed by the user running my app.</p>
  
  <p>=> the needed info is : how many files are opened right now for the current linux user.</p>
  
  <p>Has anyone managed to implement this kind of 'lsof' thing and add it to his prometheus micrometer endpoint?</p>
  
  <p>Regards,
  Guillaume</p>