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Suggestions needed for building R server REST API's that I can call from external app?
Asked Answered
rnode.jsshinyopencpurapache
P

2

19

I've seen lots of articles about consuming data in R from other RESTful API services, but I have really struggled to find any articles about the reverse. I'm interested in R being the server, and not the client. I'd like a Node.js app to call a RESTful API of an R-server so I can leverage specific analytical functions such as multi-seasonality forecasting. Anyone have any ideas?

Pileum answered 4/3, 2014 at 18:1 Comment(5)
This is pretty much the most fleshed out option I've seen in this space but there are half a dozen alternatives: opencpu.org – Hithermost
Any chance for generic curl interface? as described in the bounty. – Jury
Did you even look at the docs for OpenCPU? At the top of the API page, it explicitly states "many of the sections below contain curl examples". – Frias
@r2evans, I've played with opencpu a while ago (without success), don't know if it changed much since that time. Anyway I'm looking for a simple code to run in R, to just host the function which I can call with the curl. The examples are perfect, but there is no simple run server from R commands to type in R. If you know, please post as answer, deserved bounty will be yours! – Jury
Sorry, the comment about reading the docs was aimed at the comment that asked if it had a generic curl interface. I do think opencpu could fit the bill, though. Though not ideal, opencpu does start a single-process server for testing when you load the library interactively, and it still works remarkably well. – Frias
K
21

You can use httpuv to fire up a basic server then handle the GET/POST requests. The following isn't "REST" per se, but it should provide the basic framework:

library(httpuv)
library(RCurl)
library(httr)

app <- list(call=function(req) {

  query <- req$QUERY_STRING
  qs <- httr:::parse_query(gsub("^\\?", "", query))

  status <- 200L
  headers <- list('Content-Type' = 'text/html')

  if (!is.character(query) || identical(query, "")) {
    body <- "\r\n<html><body></body></html>"
  } else {
    body <- sprintf("\r\n<html><body>a=%s</body></html>", qs$a)
  }

  ret <- list(status=status,
              headers=headers,
              body=body)

  return(ret)

})

message("Starting server...")

server <- startServer("127.0.0.1", 8000, app=app)
on.exit(stopServer(server))

while(TRUE) {
  service()
  Sys.sleep(0.001)
}

stopServer(server)

I have the httr and RCurl packages in there since you'll probably end up needing to use some bits of both to parse/format/etc requests & responses.

Kosak answered 9/4, 2015 at 11:43 Comment(0)
I
6

node-rio provides a way to talk to rserve (a TCP/IP server that allows the use of R functions) from node.js.

Here is an example of use (from the documentation):

var rio = require('rio');
rio.evaluate("as.character('Hello World')");
Intoxicate answered 4/3, 2014 at 18:12 Comment(2)
Thanks! I found that later yesterday as well and got the basic evaluate method to work. Having trouble on the sourceAndEvaluate method when I have to pass in variables. Can you help on something as simple as: testFunction <- function(a,b) { return a+b } ? I figured out how to step debugging through it sourcing this function by path, but I can't figure out how to parameterize data IO with the function. Any ideas? – Pileum
Sorry, I am not too familiar with the actual working of node js. I mostly just know rserve. I would open up a new question. – Intoxicate

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