https with {plumber} using Caddy

Say you have a plumber API and you need to serve it over https. You can do this by spinning up a Docker container in something like DigitalOcean, Render, Heroku, or AWS ECS.

If you have you own server, you may want to use that instead. The most common way to do this is by using a reverse proxy.

Caddy is the simplest reverse proxy I am aware of.

The Plumber API

Below we define a simple plumber API. Save this file to plumber.R.

library(plumber)

pr() |>
  pr_get("/echo", function(msg = "") {
    list(msg = paste0("The message is: '", msg, "'"))
  }) |>
  pr_get("/sum", function(a, b) {
    as.numeric(a) + as.numeric(b)
  }) |>
  pr_run(port = 8888)

Serving with https

Reverse proxies are typically the most common way of adding https to a site. Many organization use nginx. Though for simplicity I recommend Caddy.

Caddy automatically implements https by default.

The below Caddyfile will serve the plumber API over https. It takes any requests to localhost and passes the request to the plumber API on port 8888, captures the response and sends it back to the client.

Tip

The https protocol requires binding to port 443.

Save this as Caddyfile

# serve the plumber API over HTTPS
localhost:443 {
    reverse_proxy localhost:8888
}

Running the API & proxy

To serve the plumber API via Caddy you need to start both processes.

(R -f plumber.R) & caddy run

This will run the plumber API in the background and then the caddy process.

Generalizing

Note that these are instructions specifically for using Caddy. However this point genealizes to all reverse proxies. They likely require more boiler plate, but will work just as well.

Resources

Andrew Heiss has a really great demo repository that is a much more advanced version of this that uses Docker and Docker Compose.

Use Valve to scale your plumber API and apply the same principles.