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