[FR] Native support for caching

[jeffkeller87]

There was a shiny blog post earlier this year describing the very useful native caching feature using the cachem package. I think it would be just as useful--if not more useful, considering performance expectations of HTTP APIs--to have a similar caching integration for plumber.

Of course, like apps built with shiny 1.6.0 and older, this can be done manually using the cachem package directly. Below is an example that keys off the URL parameters only.

cache <- cachem::cache_mem()

slow_add <- function(a, b) {
  
  Sys.sleep(5)
  return(as.numeric(a) + as.numeric(b))
  
}

pr <- plumber::pr()

pr$handle(
  methods = "GET", path = "/slow_add",
  handler = function(a, b, req, res) {
    
    slow_add(a, b)
    
  }
)

pr$handle(
  methods = "GET", path = "/slow_add_cached",
  handler = function(a, b, req, res) {
    
    key <- digest::digest(list(a, b), algo = "spookyhash")
    
    cache$get(
      key = key,
      missing = {
        
        value <- slow_add(a, b)
        cache$set(key, value)
        return(value)
        
      }
    )
    
  }
)

pr$run()