Request for code snippet - Recommended way to do request logging

[saurabhnanda]

Would it basically be a middleware based on https://hackage.haskell.org/package/wai-extra-3.0.19.1/docs/Network-Wai-Middleware-RequestLogger.html ? Will it also log time taken to complete the request?

[robertjlooby]

Yes, you can use Network.Wai.Middleware.RequestLogger. It includes a couple default loggers, or you can tweak the configs if you want. As an example:

module Main where

import Network.Wai.Middleware.RequestLogger (logStdout)
import Web.Scotty

main :: IO ()
main = do
  scotty 3000 $ do
    middleware logStdout
    ...

will produce "prod" type log statements like

Setting phasers to stun... (port 3000) (ctrl-c to quit)
127.0.0.1 - - [08/Jun/2017:18:28:02 -0500] "GET / HTTP/1.1" 200 - "" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36"
127.0.0.1 - - [08/Jun/2017:18:28:02 -0500] "GET /init HTTP/1.1" 404 - "http://localhost:3000/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36"

if you swap in logStdoutDev for logStdout you get more "dev" type log statements like

Setting phasers to stun... (port 3000) (ctrl-c to quit)
GET /
  Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
  Status: 200 OK 0.001119s
GET /init
  Accept: */*
  Status: 404 Not Found 0.000061s