R script / package to listen to an endpoint on webpage?

Question

I'm using an R script to query an API, process data, and then run it on a shiny server. Basically there's a input field, and then it queries that username. However, I'd like to do this from a discord bot. So I'm wondering if there's a way to listen to www.example.com/endpoint/ and then use the input from this endpoint into the query?

Answer 1

The solution was to use the plumber package. This essentially creates an endpoint for your script. An example:

# plumber.R

#* Echo back the input
#* @param msg The message to echo
#* @get /echo
function(msg=""){
  list(msg = paste0("The message is: '", msg, "'"))
}

Then you save that as a R-script, and use the following:

library(plumber)
r <- plumb("plumber.R")  # Where 'plumber.R' is the location of the file shown above
r$run(port=8000)

I'm running this on an Ubuntu server, where following code starts the service. In that case you don't need the lines above, only the plumber.R file since the code below in essence does the same:

sudo nano /etc/systemd/system/plumber-api.service

Content of the file should be:

[Unit]
Description=Plumber API
# After=postgresql 
# (or mariadb, mysql, etc if you use a DB with Plumber, otherwise leave this commented)

[Service]
ExecStart=/usr/bin/Rscript -e "api <- plumber::plumb('/your-dir/your-api-script.R'); api$run(port=8080, host='0.0.0.0')"
Restart=on-abnormal
WorkingDirectory=/your-dir/

[Install]
WantedBy=multi-user.target

https://www.rplumber.io/docs/hosting.html

sudo systemctl start plumber-api # starts the service

Details on the plumber package here