Я изучаю Слугу и пишу простой сервис. Вот исходный код:Слуга всегда дает мне начальное значение в ReaderT Monad
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE DeriveGeneriC#-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE RankNTypes #-}
module BigMama where
import Control.Concurrent
import Control.Concurrent.STM
import Control.Monad
import Control.Monad.Reader
import Data.Aeson
import Data.Aeson.Types
import qualified Data.ByteString.Lazy.Char8 as C
import Data.Char
import qualified Data.Map as M
import Debug.Trace
import GHC.Generics
import Prelude hiding (id)
import Servant
data MicroService = MicroService
{ name :: String
, port :: Int
, id :: Maybe String
} deriving (Generic)
instance ToJSON MicroService
instance FromJSON MicroService
instance Show MicroService where
show = C.unpack . encode
type ServiceSet = STM (TVar (M.Map String MicroService))
type LocalHandler = ReaderT ServiceSet IO
defaultServices :: ServiceSet
defaultServices = newTVar $ M.fromList []
type Api =
"bigmama" :> Get '[JSON] (Maybe MicroService)
:<|> "bigmama" :> ReqBody '[JSON] MicroService :> Post '[JSON] MicroService
api :: Proxy Api
api = Proxy
serverT :: ServerT Api LocalHandler
serverT = getService
:<|> registerService
getService :: LocalHandler (Maybe MicroService)
getService = do
stm <- ask
liftIO . atomically $ do
tvar <- stm
mss <- readTVar tvar
return $ M.lookup "file" mss
registerService :: MicroService -> LocalHandler MicroService
registerService ms = do
stm <- ask
liftIO . atomically $ do
tvar <- stm
mss <- readTVar tvar
let mss' = M.insert (name ms) ms mss
writeTVar tvar mss'
return ms
readerToHandler' :: forall a. ServiceSet -> LocalHandler a -> Handler a
readerToHandler' ss r = liftIO $ runReaderT r ss
readerToHandler :: ServiceSet -> (:~>) LocalHandler Handler
readerToHandler ss = Nat (readerToHandler' ss)
server :: Server Api
server = enter (readerToHandler defaultServices) serverT
Похоже, что слуга предлагает новую defaultServices
для каждого запроса. Я отправляю POST для создания службы (name = "file") и не может вернуть службу в GET-запрос. Как делиться данными между запросами на слугу?