R Shiny database management

Question

I have an RStudio Shiny app that saves user data in a subdirectory where my shiny app is hosted. What is the best way to store the data and access it?

The relevant part of the code is something like this:

# Save all answers after click on "submit"
observe({
  if(is.null(input$submit) || input$submit == 0) {return()}
  filename <- paste0("/data/answers-",input$userName, "-", as.numeric(Sys.time()), ".RData")
  save(values$A, file = filename, compress = "xz")
})

The app works: the data is successfully saved in the data subdirectory on the server.

Edit: I save the data as .RData, assuming that's a natural approach. If I save the data as .csv, it looks like this:

"What do you think about this?","Excellent","Excellent"
"What do you think about that?","Excellent","Excellent"
"User Unique ID","ABC123","DEF456"

except that there are more rows and more columns.

One approach would be to periodically download the data from the server and delete it on the server if it exceeds a critical size (to prevent it from taking up too much space). How best to do that?

Any tips on database management are welcome.

I am cross-posting from shiny-discuss, where my question has not yet generated any reaction:

https://groups.google.com/forum/#!topic/shiny-discuss/gOEtUsh00Qs

Answer 1

Sorry. Comment had too many characters and this is a bigger box. If you want to append data to a file (e.g., csv) that will happen per row as in the link I provided. So you should t() your data before sending to file. To have scripts run at fixed time intervals do a search for R and Cron (for mac and/or linux). It might be easier to do this in your shiny app with invalidatelater. Setup an observer that runs every hour for example. If the file is larger than X (using file.info("myfile.csv")$size) then do something (e.g., use file.copy to move it to your dropbox account if you have dropbox installed on your server. Or email it. I haven't used email with R but this looks promising.

In sum: Try some stuff and let us know if you get stuck :)