title: download count in shinyapps.io
body: <p>I have set up a shiny app that knitr's markdown PDF's based on selceted data. The generated report needs to have some sort of unique ID to be referenced in meetings.
  I understand that I can use the session ID but I need a way to count the downloads per session. 
  Is there a way of counting events outside sessions or counting the number of session ID's since first deployment? </p>