A pipeline example using MonadJob

testpipeline.hs

{-# LANGUAGE GeneralizedNewtypeDeriving #-}
import Data.Aeson

type URL = String

newtype JobServerURL i o = JobServerURL URL

class Monad m => MonadJob m where
  callJob :: (ToJSON i, FromJSON o) => JobServerURL i o -> i -> m o

newtype InputA  = C1 () deriving (Eq, Show, ToJSON, FromJSON)
newtype OutputA = C2 () deriving (Eq, Show, ToJSON, FromJSON)
newtype InputB  = C3 () deriving (Eq, Show, ToJSON, FromJSON)
newtype OutputB = C4 () deriving (Eq, Show, ToJSON, FromJSON)
newtype InputC  = C5 () deriving (Eq, Show, ToJSON, FromJSON)
newtype OutputC = C6 () deriving (Eq, Show, ToJSON, FromJSON)
newtype Input   = C7 () deriving (Eq, Show, ToJSON, FromJSON)
newtype Output  = C8 () deriving (Eq, Show, ToJSON, FromJSON)

f1 :: Input -> InputA
f2 :: Input -> OutputA -> InputB
f3 :: Input -> OutputA -> OutputB -> InputC
f4 :: Input -> OutputA -> OutputB -> OutputC -> Output
(f1, f2, f3, f4) = undefined

serverA :: JobServerURL InputA OutputA
serverA = JobServerURL "http://hostA/taskA"

serverB :: JobServerURL InputB OutputB
serverB = JobServerURL "http://hostB/taskB"

serverC :: JobServerURL InputC OutputC
serverC = JobServerURL "http://hostC/taskC"

f :: MonadJob m => Input -> m Output
f data1 = do
  data2 <- callJob serverA (f1 data1)
  data3 <- callJob serverB (f2 data1 data2)
  data4 <- callJob serverC (f3 data1 data2 data3)
  return $ f4 data1 data2 data3 data4