@@ -3,8 +3,10 @@
3{-# LANGUAGE OverloadedStrings #-}
3{-# LANGUAGE OverloadedStrings #-}
4{-# LANGUAGE PackageImports #-}
4{-# LANGUAGE PackageImports #-}
5{-# LANGUAGE PatternGuards #-}
5{-# LANGUAGE PatternGuards #-}
6+{-# LANGUAGE RecordWildCards #-}
6{-# LANGUAGE ScopedTypeVariables #-}
7{-# LANGUAGE ScopedTypeVariables #-}
7{-# LANGUAGE TupleSections #-}
8{-# LANGUAGE TupleSections #-}
9+{-# LANGUAGE ViewPatterns #-}
8{-# OPTIONS_GHC -fno-warn-deprecations #-}
10{-# OPTIONS_GHC -fno-warn-deprecations #-}
10module Network.Wai.Handler.Warp.Run where
12module Network.Wai.Handler.Warp.Run where
@@ -15,15 +17,20 @@ import qualified Control.Concurrent as Conc (yield)
15import Control.Exception as E
17import Control.Exception as E
16import qualified Data.ByteString as S
18import qualified Data.ByteString as S
17import Data.Char (chr)
19import Data.Char (chr)
18−import Data.IORef (IORef, newIORef, readIORef, writeIORef, atomicModifyIORef')
20+import Data.IORef (IORef, newIORef, readIORef, writeIORef)
19import Data.Streaming.Network (bindPortTCP)
21import Data.Streaming.Network (bindPortTCP)
20import Foreign.C.Error (Errno(..), eCONNABORTED)
22import Foreign.C.Error (Errno(..), eCONNABORTED)
21import GHC.IO.Exception (IOException(..))
23import GHC.IO.Exception (IOException(..))
24+import qualified Network.HTTP2 as H2
22import Network.Socket (Socket, close, accept, withSocketsDo, SockAddr(SockAddrInet, SockAddrInet6), setSocketOption, SocketOption(..))
25import Network.Socket (Socket, close, accept, withSocketsDo, SockAddr(SockAddrInet, SockAddrInet6), setSocketOption, SocketOption(..))
26+#if MIN_VERSION_network(3,1,1)
27+import Network.Socket (gracefulClose)
23import qualified Network.Socket.ByteString as Sock
29import qualified Network.Socket.ByteString as Sock
24import Network.Wai
30import Network.Wai
25import Network.Wai.Internal (ResponseReceived (ResponseReceived))
31import Network.Wai.Internal (ResponseReceived (ResponseReceived))
26−import System.Environment (getEnvironment)
32+import System.Environment (lookupEnv)
33+import qualified System.TimeManager as T
27import System.Timeout (timeout)
34import System.Timeout (timeout)
29import Network.Wai.Handler.Warp.Buffer
36import Network.Wai.Handler.Warp.Buffer
@@ -31,7 +38,8 @@ import Network.Wai.Handler.Warp.Counter
31import qualified Network.Wai.Handler.Warp.Date as D
38import qualified Network.Wai.Handler.Warp.Date as D
32import qualified Network.Wai.Handler.Warp.FdCache as F
39import qualified Network.Wai.Handler.Warp.FdCache as F
33import qualified Network.Wai.Handler.Warp.FileInfoCache as I
40import qualified Network.Wai.Handler.Warp.FileInfoCache as I
34−import Network.Wai.Handler.Warp.HTTP2 (http2, isHTTP2)
41+import Network.Wai.Handler.Warp.HTTP2 (http2)
42+import Network.Wai.Handler.Warp.HTTP2.Types (isHTTP2)
35import Network.Wai.Handler.Warp.Header
43import Network.Wai.Handler.Warp.Header
36import Network.Wai.Handler.Warp.Imports hiding (readInt)
44import Network.Wai.Handler.Warp.Imports hiding (readInt)
37import Network.Wai.Handler.Warp.ReadInt
45import Network.Wai.Handler.Warp.ReadInt
@@ -40,7 +48,6 @@ import Network.Wai.Handler.Warp.Request
40import Network.Wai.Handler.Warp.Response
48import Network.Wai.Handler.Warp.Response
41import Network.Wai.Handler.Warp.SendFile
49import Network.Wai.Handler.Warp.SendFile
42import Network.Wai.Handler.Warp.Settings
50import Network.Wai.Handler.Warp.Settings
43−import qualified Network.Wai.Handler.Warp.Timeout as T
44import Network.Wai.Handler.Warp.Types
51import Network.Wai.Handler.Warp.Types
@@ -51,21 +58,38 @@ import Network.Socket (fdSocket)
53-- | Creating 'Connection' for plain HTTP based on a given socket.
60-- | Creating 'Connection' for plain HTTP based on a given socket.
54−socketConnection :: Socket -> IO Connection
61+socketConnection :: Settings -> Socket -> IO Connection
62+#if MIN_VERSION_network(3,1,1)
63+socketConnection set s = do
55−socketConnection s = do
65+socketConnection _ s = do
56 bufferPool <- newBufferPool
67 bufferPool <- newBufferPool
57 writeBuf <- allocateBuffer bufferSize
68 writeBuf <- allocateBuffer bufferSize
58 let sendall = Sock.sendAll s
69 let sendall = Sock.sendAll s
70+ isH2 <- newIORef False -- HTTP/1.x
59 return Connection {
71 return Connection {
60 connSendMany = Sock.sendMany s
72 connSendMany = Sock.sendMany s
61 , connSendAll = sendall
73 , connSendAll = sendall
62 , connSendFile = sendFile s writeBuf bufferSize sendall
74 , connSendFile = sendFile s writeBuf bufferSize sendall
75+#if MIN_VERSION_network(3,1,1)
78+ let tm = if h2 then settingsGracefulCloseTimeout2 set
79+ else settingsGracefulCloseTimeout1 set
83+ gracefulClose s tm `E.catch` \(E.SomeException _) -> return ()
63 , connClose = close s
85 , connClose = close s
64 , connFree = freeBuffer writeBuf
87 , connFree = freeBuffer writeBuf
65 , connRecv = receive s bufferPool
88 , connRecv = receive s bufferPool
66 , connRecvBuf = receiveBuf s
89 , connRecvBuf = receiveBuf s
67 , connWriteBuffer = writeBuf
90 , connWriteBuffer = writeBuf
68 , connBufferSize = bufferSize
91 , connBufferSize = bufferSize
71-- | Run an 'Application' on the given port.
95-- | Run an 'Application' on the given port.
@@ -80,7 +104,7 @@ run p = runSettings defaultSettings { settingsPort = p }
80-- Since 3.0.9
104-- Since 3.0.9
81runEnv :: Port -> Application -> IO ()
105runEnv :: Port -> Application -> IO ()
82runEnv p app = do
106runEnv p app = do
83− mp <- lookup "PORT" <$> getEnvironment
107+ mp <- lookupEnv "PORT"
85 maybe (run p app) runReadPort mp
109 maybe (run p app) runReadPort mp
@@ -127,7 +151,7 @@ runSettingsSocket set socket app = do
127 setSocketCloseOnExec s
151 setSocketCloseOnExec s
128 -- NoDelay causes an error for AF_UNIX.
152 -- NoDelay causes an error for AF_UNIX.
129 setSocketOption s NoDelay 1 `E.catch` \(E.SomeException _) -> return ()
153 setSocketOption s NoDelay 1 `E.catch` \(E.SomeException _) -> return ()
130− conn <- socketConnection s
154+ conn <- socketConnection set s
131 return (conn, sa)
155 return (conn, sa)
133 closeListenSocket = close socket
157 closeListenSocket = close socket
@@ -168,15 +192,15 @@ runSettingsConnectionMakerSecure :: Settings -> IO (IO (Connection, Transport),
168runSettingsConnectionMakerSecure set getConnMaker app = do
192runSettingsConnectionMakerSecure set getConnMaker app = do
169 settingsBeforeMainLoop set
193 settingsBeforeMainLoop set
170 counter <- newCounter
194 counter <- newCounter
171− withII0 $ acceptConnection set getConnMaker app counter
195+ withII $ acceptConnection set getConnMaker app counter
173− withII0 action =
197+ withII action =
174 withTimeoutManager $ \tm ->
198 withTimeoutManager $ \tm ->
175 D.withDateCache $ \dc ->
199 D.withDateCache $ \dc ->
176 F.withFdCache fdCacheDurationInSeconds $ \fdc ->
200 F.withFdCache fdCacheDurationInSeconds $ \fdc ->
177 I.withFileInfoCache fdFileInfoDurationInSeconds $ \fic -> do
201 I.withFileInfoCache fdFileInfoDurationInSeconds $ \fic -> do
178− let ii0 = InternalInfo0 tm dc fdc fic
202+ let ii = InternalInfo tm dc fdc fic
179− action ii0
203+ action ii
181 !fdCacheDurationInSeconds = settingsFdCacheDuration set * 1000000
205 !fdCacheDurationInSeconds = settingsFdCacheDuration set * 1000000
182 !fdFileInfoDurationInSeconds = settingsFileInfoCacheDuration set * 1000000
206 !fdFileInfoDurationInSeconds = settingsFileInfoCacheDuration set * 1000000
@@ -205,9 +229,9 @@ acceptConnection :: Settings
205 -> IO (IO (Connection, Transport), SockAddr)
229 -> IO (IO (Connection, Transport), SockAddr)
206 -> Application
230 -> Application
207 -> Counter
231 -> Counter
208− -> InternalInfo0
232+ -> InternalInfo
210−acceptConnection set getConnMaker app counter ii0 = do
234+acceptConnection set getConnMaker app counter ii = do
211 -- First mask all exceptions in acceptLoop. This is necessary to
235 -- First mask all exceptions in acceptLoop. This is necessary to
212 -- ensure that no async exception is throw between the call to
236 -- ensure that no async exception is throw between the call to
213 -- acceptNewConnection and the registering of connClose.
237 -- acceptNewConnection and the registering of connClose.
@@ -234,7 +258,7 @@ acceptConnection set getConnMaker app counter ii0 = do
234 case mx of
258 case mx of
235 Nothing -> return ()
259 Nothing -> return ()
236 Just (mkConn, addr) -> do
260 Just (mkConn, addr) -> do
237− fork set mkConn addr app counter ii0
261+ fork set mkConn addr app counter ii
238 acceptLoop
262 acceptLoop
240 acceptNewConnection = do
264 acceptNewConnection = do
@@ -257,15 +281,12 @@ fork :: Settings
257 -> SockAddr
281 -> SockAddr
258 -> Application
282 -> Application
259 -> Counter
283 -> Counter
260− -> InternalInfo0
284+ -> InternalInfo
262−fork set mkConn addr app counter ii0 = settingsFork set $ \unmask ->
286+fork set mkConn addr app counter ii = settingsFork set $ \unmask ->
263 -- Call the user-supplied on exception code if any
287 -- Call the user-supplied on exception code if any
264 -- exceptions are thrown.
288 -- exceptions are thrown.
265− handle (settingsOnException set Nothing) .
289+ handle (settingsOnException set Nothing) $
266− -- Allocate a new IORef indicating whether the connection has been
267− -- closed, to avoid double-freeing a connection
268− withClosedRef $ \ref ->
269 -- Run the connection maker to get a new connection, and ensure
290 -- Run the connection maker to get a new connection, and ensure
270 -- that the connection is closed. If the mkConn call throws an
291 -- that the connection is closed. If the mkConn call throws an
271 -- exception, we will leak the connection. If the mkConn call is
292 -- exception, we will leak the connection. If the mkConn call is
@@ -276,24 +297,15 @@ fork set mkConn addr app counter ii0 = settingsFork set $ \unmask ->
276 -- We grab the connection before registering timeouts since the
297 -- We grab the connection before registering timeouts since the
277 -- timeouts will be useless during connection creation, due to the
298 -- timeouts will be useless during connection creation, due to the
278 -- fact that async exceptions are still masked.
299 -- fact that async exceptions are still masked.
279− bracket mkConn (cleanUp ref) (serve unmask ref)
300+ bracket mkConn cleanUp (serve unmask)
281− withClosedRef inner = newIORef False >>= inner
283− closeConn ref conn = do
284− isClosed <- atomicModifyIORef' ref $ \x -> (True, x)
285− unless isClosed $ connClose conn
287− cleanUp ref (conn, _) = closeConn ref conn `finally` connFree conn
302+ cleanUp (conn, _) = connClose conn `finally` connFree conn
289 -- We need to register a timeout handler for this thread, and
304 -- We need to register a timeout handler for this thread, and
290− -- cancel that handler as soon as we exit. We additionally close
305+ -- cancel that handler as soon as we exit.
291− -- the connection immediately in case the child thread catches the
292− -- async exception or performs some long-running cleanup action.
293− serve unmask ref (conn, transport) = bracket register cancel $ \th -> do
306+ serve unmask (conn, transport) = bracket register cancel $ \th -> do
294− let ii1 = toInternalInfo1 ii0 th
295 -- We now have fully registered a connection close handler in
307 -- We now have fully registered a connection close handler in
296− -- the case of all exceptions, so it is safe to one again
308+ -- the case of all exceptions, so it is safe to once again
297 -- allow async exceptions.
309 -- allow async exceptions.
299 -- Call the user-supplied code for connection open and
311 -- Call the user-supplied code for connection open and
@@ -301,23 +313,23 @@ fork set mkConn addr app counter ii0 = settingsFork set $ \unmask ->
301 bracket (onOpen addr) (onClose addr) $ \goingon ->
313 bracket (onOpen addr) (onClose addr) $ \goingon ->
302 -- Actually serve this connection. bracket with closeConn
314 -- Actually serve this connection. bracket with closeConn
303 -- above ensures the connection is closed.
315 -- above ensures the connection is closed.
304− when goingon $ serveConnection conn ii1 addr transport set app
316+ when goingon $ serveConnection conn ii th addr transport set app
306− register = T.registerKillThread (timeoutManager0 ii0)
318+ register = T.registerKillThread (timeoutManager ii) (connClose conn)
307− (closeConn ref conn)
308 cancel = T.cancel
319 cancel = T.cancel
310 onOpen adr = increase counter >> settingsOnOpen set adr
321 onOpen adr = increase counter >> settingsOnOpen set adr
311 onClose adr _ = decrease counter >> settingsOnClose set adr
322 onClose adr _ = decrease counter >> settingsOnClose set adr
313serveConnection :: Connection
324serveConnection :: Connection
314− -> InternalInfo1
325+ -> InternalInfo
315 -> SockAddr
327 -> SockAddr
316 -> Transport
328 -> Transport
317 -> Settings
329 -> Settings
318 -> Application
330 -> Application
320−serveConnection conn ii1 origAddr transport settings app = do
332+serveConnection conn ii th origAddr transport settings app = do
321 -- fixme: Upgrading to HTTP/2 should be supported.
333 -- fixme: Upgrading to HTTP/2 should be supported.
322 (h2,bs) <- if isHTTP2 transport then
334 (h2,bs) <- if isHTTP2 transport then
323 return (True, "")
335 return (True, "")
@@ -330,22 +342,35 @@ serveConnection conn ii1 origAddr transport settings app = do
330 istatus <- newIORef False
342 istatus <- newIORef False
331 if settingsHTTP2Enabled settings && h2 then do
343 if settingsHTTP2Enabled settings && h2 then do
332 rawRecvN <- makeReceiveN bs (connRecv conn) (connRecvBuf conn)
344 rawRecvN <- makeReceiveN bs (connRecv conn) (connRecvBuf conn)
345+ -- This thread becomes the sender in http2 library.
346+ -- In the case of event source, one request comes and one
347+ -- worker gets busy. But it is likely that the receiver does
348+ -- not receive any data at all while the sender is sending
349+ -- output data from the worker. It's not good enough to tickle
350+ -- the time handler in the receiver only. So, we should tickle
351+ -- the time handler in both the receiver and the sender.
333 let recvN = wrappedRecvN th istatus (settingsSlowlorisSize settings) rawRecvN
352 let recvN = wrappedRecvN th istatus (settingsSlowlorisSize settings) rawRecvN
353+ sendBS x = connSendAll conn x >> T.tickle th
334 -- fixme: origAddr
354 -- fixme: origAddr
356+ setConnHTTP2 conn True
335− http2 conn ii1 origAddr transport settings recvN app
357+ http2 conn transport ii origAddr settings recvN sendBS app
337 src <- mkSource (wrappedRecv conn th istatus (settingsSlowlorisSize settings))
359 src <- mkSource (wrappedRecv conn th istatus (settingsSlowlorisSize settings))
338 writeIORef istatus True
360 writeIORef istatus True
339 leftoverSource src bs
361 leftoverSource src bs
340 addr <- getProxyProtocolAddr src
362 addr <- getProxyProtocolAddr src
341 http1 True addr istatus src `E.catch` \e ->
363 http1 True addr istatus src `E.catch` \e ->
342− case fromException e of
364+ case () of
343− -- See comment below referencing
366+ -- See comment below referencing
344− -- https://github.com/yesodweb/wai/issues/618
367+ -- https://github.com/yesodweb/wai/issues/618
345− Just NoKeepAliveRequest -> return ()
368+ | Just NoKeepAliveRequest <- fromException e -> return ()
346− Nothing -> do
369+ -- No valid request
370+ | Just (BadFirstLine _) <- fromException e -> return ()
347− sendErrorResponse (dummyreq addr) istatus e
372+ _ <- sendErrorResponse (dummyreq addr) istatus e
348− throwIO e
373+ throwIO e
351 getProxyProtocolAddr src =
376 getProxyProtocolAddr src =
@@ -388,29 +413,25 @@ serveConnection conn ii1 origAddr transport settings app = do
389 decodeAscii = map (chr . fromEnum) . S.unpack
414 decodeAscii = map (chr . fromEnum) . S.unpack
391− th = threadHandle1 ii1
393 shouldSendErrorResponse se
416 shouldSendErrorResponse se
394 | Just ConnectionClosedByPeer <- fromException se = False
417 | Just ConnectionClosedByPeer <- fromException se = False
395 | otherwise = True
418 | otherwise = True
397 sendErrorResponse req istatus e = do
420 sendErrorResponse req istatus e = do
398 status <- readIORef istatus
421 status <- readIORef istatus
399− when (shouldSendErrorResponse e && status) $ do
422+ if shouldSendErrorResponse e && status
400− let ii = toInternalInfo ii1 0 -- dummy
423+ then do
401− void $ sendResponse settings conn ii req defaultIndexRequestHeader (return S.empty) (errorResponse e)
424+ sendResponse settings conn ii th req defaultIndexRequestHeader (return S.empty) (errorResponse e)
403 dummyreq addr = defaultRequest { remoteHost = addr }
427 dummyreq addr = defaultRequest { remoteHost = addr }
405 errorResponse e = settingsOnExceptionResponse settings e
429 errorResponse e = settingsOnExceptionResponse settings e
407 http1 firstRequest addr istatus src = do
431 http1 firstRequest addr istatus src = do
408− (req', mremainingRef, idxhdr, nextBodyFlush, ii) <- recvRequest firstRequest settings conn ii1 addr src
432+ (req, mremainingRef, idxhdr, nextBodyFlush) <- recvRequest firstRequest settings conn ii th addr src transport
409− let req = req' { isSecure = isTransportSecure transport }
410− keepAlive <- processRequest istatus src req mremainingRef idxhdr nextBodyFlush ii
433+ keepAlive <- processRequest istatus src req mremainingRef idxhdr nextBodyFlush
411 `E.catch` \e -> do
434 `E.catch` \e -> do
412− -- Call the user-supplied exception handlers, passing the request.
413− sendErrorResponse req istatus e
414 settingsOnException settings (Just req) e
435 settingsOnException settings (Just req) e
415 -- Don't throw the error again to prevent calling settingsOnException twice.
436 -- Don't throw the error again to prevent calling settingsOnException twice.
416 return False
437 return False
@@ -425,7 +446,7 @@ serveConnection conn ii1 origAddr transport settings app = do
425 -- and ignore. See: https://github.com/yesodweb/wai/issues/618
446 -- and ignore. See: https://github.com/yesodweb/wai/issues/618
426 when keepAlive $ http1 False addr istatus src
447 when keepAlive $ http1 False addr istatus src
428− processRequest istatus src req mremainingRef idxhdr nextBodyFlush ii = do
449+ processRequest istatus src req mremainingRef idxhdr nextBodyFlush = do
429 -- Let the application run for as long as it wants
450 -- Let the application run for as long as it wants
430 T.pause th
451 T.pause th
@@ -433,30 +454,38 @@ serveConnection conn ii1 origAddr transport settings app = do
433 -- creating the request, we need to make sure that we don't get
454 -- creating the request, we need to make sure that we don't get
434 -- an async exception before calling the ResponseSource.
455 -- an async exception before calling the ResponseSource.
435 keepAliveRef <- newIORef $ error "keepAliveRef not filled"
456 keepAliveRef <- newIORef $ error "keepAliveRef not filled"
436− _ <- app req $ \res -> do
457+ r <- E.try $ app req $ \res -> do
437 T.resume th
458 T.resume th
438 -- FIXME consider forcing evaluation of the res here to
459 -- FIXME consider forcing evaluation of the res here to
439 -- send more meaningful error messages to the user.
460 -- send more meaningful error messages to the user.
440 -- However, it may affect performance.
461 -- However, it may affect performance.
441 writeIORef istatus False
462 writeIORef istatus False
442− keepAlive <- sendResponse settings conn ii req idxhdr (readSource src) res
463+ keepAlive <- sendResponse settings conn ii th req idxhdr (readSource src) res
443 writeIORef keepAliveRef keepAlive
464 writeIORef keepAliveRef keepAlive
444 return ResponseReceived
465 return ResponseReceived
467+ Right ResponseReceived -> return ()
468+ Left e@(SomeException _)
469+ | Just (ExceptionInsideResponseBody e') <- fromException e -> throwIO e'
471+ keepAlive <- sendErrorResponse req istatus e
472+ settingsOnException settings (Just req) e
473+ writeIORef keepAliveRef keepAlive
445 keepAlive <- readIORef keepAliveRef
475 keepAlive <- readIORef keepAliveRef
447 -- We just send a Response and it takes a time to
477 -- We just send a Response and it takes a time to
448 -- receive a Request again. If we immediately call recv,
478 -- receive a Request again. If we immediately call recv,
449− -- it is likely to fail and the IO manager works.
479+ -- it is likely to fail and cause the IO manager to do some work.
450− -- It is very costly. So, we yield to another Haskell
480+ -- It is very costly, so we yield to another Haskell
451 -- thread hoping that the next Request will arrive
481 -- thread hoping that the next Request will arrive
452 -- when this Haskell thread will be re-scheduled.
482 -- when this Haskell thread will be re-scheduled.
453 -- This improves performance at least when
483 -- This improves performance at least when
454 -- the number of cores is small.
484 -- the number of cores is small.
455 Conc.yield
485 Conc.yield
457− if not keepAlive then
487+ if keepAlive
458− return False
488+ then
460 -- If there is an unknown or large amount of data to still be read
489 -- If there is an unknown or large amount of data to still be read
461 -- from the request body, simple drop this connection instead of
490 -- from the request body, simple drop this connection instead of
462 -- reading it all in to satisfy a keep-alive request.
491 -- reading it all in to satisfy a keep-alive request.
@@ -482,6 +511,21 @@ serveConnection conn ii1 origAddr transport settings app = do
483 return False
512 return False
484 Nothing -> tryKeepAlive
513 Nothing -> tryKeepAlive
517+ checkTLS = case transport of
518+ TCP -> return () -- direct
519+ tls -> unless (tls12orLater tls) $ goaway conn H2.InadequateSecurity "Weak TLS"
520+ tls12orLater tls = tlsMajorVersion tls == 3 && tlsMinorVersion tls >= 3
522+-- connClose must not be called here since Run:fork calls it
523+goaway :: Connection -> H2.ErrorCodeId -> ByteString -> IO ()
524+goaway Connection{..} etype debugmsg = connSendAll bytestream
526+ einfo = H2.encodeInfo id 0
527+ frame = H2.GoAwayFrame 0 etype debugmsg
528+ bytestream = H2.encodeFrame einfo frame
486flushEntireBody :: IO ByteString -> IO ()
530flushEntireBody :: IO ByteString -> IO ()
487flushEntireBody src =
531flushEntireBody src =
@@ -536,7 +580,13 @@ setSocketCloseOnExec :: Socket -> IO ()
536#if WINDOWS
580#if WINDOWS
537setSocketCloseOnExec _ = return ()
581setSocketCloseOnExec _ = return ()
583+setSocketCloseOnExec socket = do
584+#if MIN_VERSION_network(3,0,0)
585+ fd <- fdSocket socket
587+ let fd = fdSocket socket
539−setSocketCloseOnExec socket = F.setFileCloseOnExec $ fromIntegral $ fdSocket socket
589+ F.setFileCloseOnExec $ fromIntegral fd
542gracefulShutdown :: Settings -> Counter -> IO ()
592gracefulShutdown :: Settings -> Counter -> IO ()