connection-manager: numberOfConnections

For connection manager which allows to include inbound connections we
need a method to count how many connections are currently included (for
rate limiting).  We count all connection, weather inbound or outbound.
In future we could count only inbound connections, but this will require
to know the state of mux (to know when on-demand responders actaully
started).

ouroboros-network-framework/src/Ouroboros/Network/ConnectionManager/Core.hs

@@ -114,13 +114,23 @@ withConnectionManager ConnectionManagerArguments {
             ConnectionHandler (WithResponderMode inboundHandler) ->
               ConnectionManager
                 (WithResponderMode
-                  (includeConnection stateVar mainThreadId inboundHandler Inbound))
+                  InboundConnectionManager {
+                      icmIncludeConnection =
+                        includeConnection stateVar mainThreadId inboundHandler Inbound,
+                      icmNumberOfConnections =
+                        countConnections stateVar
+                    })
 
             ConnectionHandler (WithInitiatorResponderMode outboundHandler inboundHandler) ->
               ConnectionManager
                 (WithInitiatorResponderMode
                   (connectAndInclude stateVar mainThreadId outboundHandler)
-                  (includeConnection stateVar mainThreadId inboundHandler Inbound))
+                  InboundConnectionManager {
+                      icmIncludeConnection =
+                        includeConnection stateVar mainThreadId inboundHandler Inbound,
+                      icmNumberOfConnections =
+                        countConnections stateVar
+                    })
 
     k connectionManager
       `finally` do
@@ -132,6 +142,9 @@ withConnectionManager ConnectionManagerArguments {
               >> close connectionSnocket chSocket )
           state
   where
+    countConnections :: StrictTMVar m (State peerAddr socket muxPromise m) -> STM m Int
+    countConnections stateVar = Map.size <$> readTMVar stateVar
+
     -- Include a connection in the 'State'; we use this for both inbound and
     -- outbound (via 'connectAndInclude' below) connections.
     --

ouroboros-network-framework/src/Ouroboros/Network/ConnectionManager/Types.hs

@@ -19,10 +19,12 @@ module Ouroboros.Network.ConnectionManager.Types
   , ConnectionManagerArguments (..)
     -- * 'ConnectionManager'
   , ConnectionManager (..)
+  , InboundConnectionManager (..)
   , IncludeOutboundConnection
   , includeOutboundConnection
   , IncludeInboundConnection
   , includeInboundConnection
+  , numberOfConnections
     -- * Exceptions
   , ExceptionInHandler (..)
     -- * Mux types
@@ -188,6 +190,19 @@ type IncludeInboundConnection  socket peerAddr muxPromise m
     = socket -> peerAddr -> m (STM m muxPromise)
 
 
+-- | Inbound connection manager.  For a server implementation we also need to
+-- know how many connections are now managed by the connection manager.
+--
+-- This type is an internal detail of 'Ouroboros.Network.ConnectionManager'
+--
+data InboundConnectionManager (muxMode :: MuxMode) socket peerAddr muxPromise m where
+    InboundConnectionManager
+      :: HasResponder muxMode ~ True
+      => { icmIncludeConnection   :: IncludeInboundConnection socket peerAddr muxPromise m
+         , icmNumberOfConnections :: STM m Int
+         }
+      -> InboundConnectionManager muxMode socket peerAddr muxPromise m
+
 -- | 'ConnectionManager'.
 --
 -- We identify resources (e.g. 'Network.Socket.Socket') by their address.   It
@@ -198,10 +213,14 @@ type IncludeInboundConnection  socket peerAddr muxPromise m
 --
 newtype ConnectionManager (muxMode :: MuxMode) socket peerAddr muxPromise m = ConnectionManager {
     runConnectionManager
-      :: WithMuxMode muxMode (IncludeOutboundConnection        peerAddr muxPromise m)
-                             (IncludeInboundConnection  socket peerAddr muxPromise m)
+      :: WithMuxMode muxMode (IncludeOutboundConnection                 peerAddr muxPromise m)
+                             (InboundConnectionManager  muxMode socket peerAddr muxPromise m)
   }
 
+--
+-- ConnectionManager API
+--
+
 -- | Include outbound connection into 'ConnectionManager'.
 --
 includeOutboundConnection :: HasInitiator muxMode ~ True
@@ -212,10 +231,21 @@ includeOutboundConnection = withInitiatorMode . runConnectionManager
 -- | Include an inbound connection into 'ConnectionManager'.
 --
 includeInboundConnection :: HasResponder muxMode ~ True
-                          => ConnectionManager muxMode socket peerAddr muxPromise m
-                          -> IncludeInboundConnection  socket peerAddr muxPromise m
-includeInboundConnection = withResponderMode . runConnectionManager
+                         => ConnectionManager muxMode socket peerAddr muxPromise m
+                         -> IncludeInboundConnection  socket peerAddr muxPromise m
+includeInboundConnection =  icmIncludeConnection . withResponderMode . runConnectionManager
 
+-- | Number of currently included connections.
+--
+-- Note: we count all connection: both inbound and outbound.  In a future
+-- version we could count only inbound connections, but this will require
+-- tracking state inside mux if the responder side has started running (through
+-- on-demand interface).  This is currently not exposed by mux.
+--
+numberOfConnections :: HasResponder muxMode ~ True
+                    => ConnectionManager muxMode socket peerAddr muxPromise m
+                    -> STM m Int
+numberOfConnections = icmNumberOfConnections . withResponderMode . runConnectionManager
 
 --
 -- Tracing