Make waitStream update connection flow control window.

ChangeLog.md

@@ -2,6 +2,9 @@
 
 ## Unreleased changes
 
+- Change `waitStream` so that it automatically credits the connection. This
+  is a breaking change due to function signature change.
+
 ## v0.10.0.0
 
 - Export frameHttp2RawConnection to convert an RawHttp2Connection into an Http2FrameConnection.

examples/SimpleGet.lhs

@@ -85,7 +85,7 @@ client-originated streams (however with its own flow-control context).
 >             resetPushPromises _ pps _ _ _ = _rst pps RefusedStream
 >
 >             handler sfc _ = do
->                 waitStream stream sfc resetPushPromises >>= print . fromStreamResult
+>                 waitStream conn stream sfc resetPushPromises >>= print . fromStreamResult
 
 We've defined an initializer and a handler so far.
 

src/Network/HTTP2/Client/Helpers.hs

@@ -115,12 +115,16 @@ upload dat flagmod conn connectionFlowControl stream streamFlowControl = do
 --
 -- This function is fine if you don't want to consume results in chunks.  See
 -- 'fromStreamResult' to collect the complicated 'StreamResult' into a simpler
--- 'StramResponse'.
-waitStream :: Http2Stream
+-- 'StreamResponse'.
+waitStream :: Http2Client
+           -- ^The connection.
+           -> Http2Stream
+           -- ^The stream to wait on. This stream must be part of the connection.
            -> IncomingFlowControl
+           -- ^Incoming flow control for the __stream__.
            -> PushPromiseHandler
            -> ClientIO StreamResult
-waitStream stream streamFlowControl ppHandler = do
+waitStream conn stream streamFlowControl ppHandler = do
     ev <- _waitEvent stream
     case ev of
         StreamHeadersEvent fH hdrs
@@ -131,20 +135,31 @@ waitStream stream streamFlowControl ppHandler = do
                 return (Right hdrs, reverse dfrms, trls)
         StreamPushPromiseEvent _ ppSid ppHdrs -> do
             _handlePushPromise stream ppSid ppHdrs ppHandler
-            waitStream stream streamFlowControl ppHandler
+            waitStream conn stream streamFlowControl ppHandler
         _ ->
             error $ "expecting StreamHeadersEvent but got " ++ show ev
   where
+    connFlowControl = _incomingFlowControl conn
     waitDataFrames xs = do
         ev <- _waitEvent stream
         case ev of
             StreamDataEvent fh x
                 | HTTP2.testEndStream (HTTP2.flags fh) ->
                     return ((Right x):xs, Nothing)
                 | otherwise                            -> do
-                    _ <- lift $ _consumeCredit streamFlowControl (HTTP2.payloadLength fh)
-                    lift $ _addCredit streamFlowControl (HTTP2.payloadLength fh)
+                    let size = HTTP2.payloadLength fh
+                    _ <- lift $ _consumeCredit streamFlowControl size
+                    lift $ _addCredit streamFlowControl size
                     _ <- _updateWindow $ streamFlowControl
+                    -- We also send a WINDOW_UPDATE for the connection in order
+                    -- to not rely on external updateWindow calls. This reduces
+                    -- latency and makes the function less error-prone to use.
+                    -- Note that the main loop (dispatchLoop) already credits
+                    -- the connection for received data frames, but it does not
+                    -- send the WINDOW_UPDATE frames.. That is why we only send
+                    -- those frames here, and we do not credit the connection
+                    --  as we do the stream in the preceding lines.
+                    _ <- _updateWindow $ connFlowControl
                     waitDataFrames ((Right x):xs)
             StreamPushPromiseEvent _ ppSid ppHdrs -> do
                 _handlePushPromise stream ppSid ppHdrs ppHandler