servant/servant-server/test/Servant/Server/StreamingSpec.hs

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{-# LANGUAGE DataKinds #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TupleSections #-}
{-# LANGUAGE TypeOperators #-}
-- | This module tests whether streaming works from client to server
-- with a server implemented with servant-server.
module Servant.Server.StreamingSpec where
import Control.Concurrent
import Control.Exception hiding (Handler)
import Control.Monad.IO.Class
import qualified Data.ByteString as Strict
import qualified Data.ByteString.Lazy as Lazy
import Network.HTTP.Types
import Network.Wai
import Network.Wai.Internal
import Prelude ()
import Prelude.Compat
import Servant
import qualified System.Timeout
import Test.Hspec
type TestAPI =
ReqBody '[OctetStream] Lazy.ByteString :> Get '[JSON] NoContent
testAPI :: Proxy TestAPI
testAPI = Proxy
spec :: Spec
spec = do
-- The idea of this test is this:
--
-- - The mock client will
-- - send some data in the request body, but not all,
-- - wait for the server to acknowledge (outside of http, through an MVar)
-- that the server received some data,
-- - send the rest of the request body.
-- - The mock server will
-- - receive some data,
-- - notify the client that it received some data,
-- - receive the rest of the data,
-- - respond with an empty result.
it "client to server can stream lazy ByteStrings" $ timeout $ do
serverReceivedFirstChunk <- newWaiter
-- - streams some test data
-- - waits for serverReceivedFirstChunk
-- - streams some more test data
streamTestData <- do
mvar :: MVar [IO Strict.ByteString] <- newMVar $
map return (replicate 1000 "foo") ++
(waitFor serverReceivedFirstChunk >> return "foo") :
map return (replicate 1000 "foo")
return $ modifyMVar mvar $ \ actions -> case actions of
(a : r) -> (r, ) <$> a
[] -> return ([], "")
let request = defaultRequest {
requestBody = streamTestData,
requestBodyLength = ChunkedBody
}
-- - receives the first chunk
-- - notifies serverReceivedFirstChunk
-- - receives the rest of the request
let handler :: Lazy.ByteString -> Handler NoContent
handler input = liftIO $ do
let prefix = Lazy.take 3 input
prefix `shouldBe` "foo"
notify serverReceivedFirstChunk ()
input `shouldBe` mconcat (replicate 2001 "foo")
return NoContent
app = serve testAPI handler
response <- executeRequest app request
statusCode (responseStatus response) `shouldBe` 200
executeRequest :: Application -> Request -> IO Response
executeRequest app request = do
responseMVar <- newEmptyMVar
let respond response = do
putMVar responseMVar response
return ResponseReceived
ResponseReceived <- app request respond
takeMVar responseMVar
timeout :: IO a -> IO a
timeout action = do
result <- System.Timeout.timeout 1000000 action
maybe (throwIO $ ErrorCall "timeout") return result
-- * waiter
data Waiter a
= Waiter {
notify :: a -> IO (),
waitFor :: IO a
}
newWaiter :: IO (Waiter a)
newWaiter = do
mvar <- newEmptyMVar
return $ Waiter {
notify = putMVar mvar,
waitFor = readMVar mvar
}