The server in Hyper.Node.Server wraps the http module in NodeJS, and serves middleware using the Aff monad. Here is how you can start a Node server:

  app =
    writeStatus (Tuple 200 "OK")
    :*> closeHeaders
    :*> respond "Hello there!"
in runServer defaultOptions {} app

As seen above, runServer takes a record of options, an initial components record, and your application middleware. If you want to do logging on server startup, and on any request handling errors, use defaultOptionsWithLogging.

Monad Transformers

You might want to use a monad transformer stack in your application, for instance as a way to pass configuration, or to accumulate some state in the chain of middleware. The underlying monad of Middleware is parameterized for this exact purpose. When running the NodeJS server with monad transformers, you need to use runServer' instead of the regular runServer, and pass a function that runs your monad and returns an Aff value.

The following code runs a middleware using the ReaderT monad transformer. Note that the runAppM function might need to be defined at the top-level to please the type checker.

type MyConfig = { thingToSay :: String }

  :: forall e a.
    ReaderT MyConfig (Aff e) a
  -> Aff e a
runAppM = flip runReaderT { thingToSay: "Hello, ReaderT!" }

main :: forall e. Eff (console :: CONSOLE, http :: HTTP | e) Unit
main =
  let app =
        lift' ask :>>= \config ->
          writeStatus statusOK
          :*> closeHeaders
          :*> respond config.thingToSay
  in runServer' defaultOptionsWithLogging {} runAppM app

In a real-world application the configuration type MyConfig could hold a database connection pool, or settings read from the environment, for example.