process and respond to join requests

- serialiseMessage now starts numbering parts from the first number it
  gets, to be able to continue responding after having ACKed previous
  parts

contributes to #28

src/Hash2Pub/ASN1Coding.hs

@@ -107,7 +107,7 @@ serialiseMessage maxBytesLength msg =
                            }):pls
         -- part starts at 1
         payloadParts :: Int -> Maybe [(Integer, ActionPayload)]
-        payloadParts i = zip [1..] . splitPayload i <$> actionPayload
+        payloadParts i = zip [(part msg)..] . splitPayload i <$> actionPayload
         actionPayload = payload msg
         encodedMsgs i = Map.map encodeMsg $ messageParts i
         maxMsgLength = maximum . fmap BS.length . Map.elems

src/Hash2Pub/DHTProtocol.hs

@@ -27,9 +27,9 @@ module Hash2Pub.DHTProtocol
 
 import           Control.Concurrent.Async
 import           Control.Concurrent.STM
-import           Control.Concurrent.STM.TVar
 import           Control.Concurrent.STM.TBQueue
 import           Control.Concurrent.STM.TQueue
+import           Control.Concurrent.STM.TVar
 import           Control.Exception
 import           Control.Monad                  (foldM, forM, forM_)
 import qualified Data.ByteString                as BS
@@ -170,6 +170,8 @@ ackRequest ownID req@Request{} = serialiseMessage sendMessageSize $ Response {
                                                                              }
 
 
+-- | Dispatch incoming requests to the dedicated handling and response function, and enqueue
+-- the response to be sent.
 handleIncomingRequest :: LocalNodeStateSTM                     -- ^ the handling node
                       -> TQueue (BS.ByteString, SockAddr)   -- ^ send queue
                       -> Set.Set FediChordMessage           -- ^ all parts of the request to handle
@@ -187,32 +189,74 @@ handleIncomingRequest nsSTM sendQ msgSet sourceAddr = do
         maybe (pure ()) (
             mapM_ (\resp -> atomically $ writeTQueue sendQ (resp, sourceAddr))
                         )
-            (case action aPart of
+            =<< (case action aPart of
-                  _ -> Just Map.empty) -- placeholder
+--                Ping -> Just <$> respondPing nsSTM msgSet
---                Ping -> Just  respondPing nsSTM msgSet
+                Join -> Just <$> respondJoin nsSTM msgSet
---                Join -> Just respondJoin nsSTM msgSet
 --                -- ToDo: figure out what happens if not joined
---                QueryID -> Just respondQueryID nsSTM msgSet
+--                QueryID -> Just <$> respondQueryID nsSTM msgSet
 --                -- only when joined
---                Leave -> if isJoined_ ns then Just respondLeave nsSTM msgSet else Nothing
+--                Leave -> if isJoined_ ns then Just <$> respondLeave nsSTM msgSet else Nothing
 --                -- only when joined
---                Stabilise -> if isJoined_ ns then Just respondStabilise nsSTM msgSet else Nothing
+--                Stabilise -> if isJoined_ ns then Just <$> respondStabilise nsSTM msgSet else Nothing
 --            )
---      -- for single part request, response starts with part number 1. For multipart requests, response starts with part number n+1.
+      -- for single part request, response starts with part number 1. For multipart requests, response starts with part number n+1.
---
+
---      -- TODO: determine request type only from first part, but catch RecSelError on each record access when folding, because otherwise different request type parts can make this crash
+      -- TODO: determine request type only from first part, but catch RecSelError on each record access when folding, because otherwise different request type parts can make this crash
---      -- TODO: test case: mixed message types of parts
+      -- TODO: test case: mixed message types of parts
---
+
----- ....... response sending .......
+            ) -- placeholder
---
+
----- this modifies node state, so locking and IO seems to be necessary.
+
----- Still try to keep as much code as possible pure
+-- ....... response sending .......
---respondJoin :: LocalNodeStateSTM -> Set.Set FediChordMessage -> Map Integer BS.ByteString
+
---respondJoin nsSTM msgSet =
+-- this modifies node state, so locking and IO seems to be necessary.
---    -- check whether the joining node falls into our responsibility
+-- Still try to keep as much code as possible pure
---    -- if yes, adjust own predecessors/ successors and return those in a response
+respondJoin :: LocalNodeStateSTM -> Set.Set FediChordMessage -> IO (Map.Map Integer BS.ByteString)
---    -- if no: empty response or send a QueryID forwards response?
+respondJoin nsSTM msgSet = do
---    -- TODO: notify service layer to copy over data now handled by the new joined node
+    -- atomically read and modify the node state according to the parsed request
+    responseMsg <- atomically $ do
+        nsSnap <- readTVar nsSTM
+        cache <- readTVar $ nodeCacheSTM nsSnap
+        let
+            aRequestPart = Set.elemAt 0 msgSet
+            senderNS = sender aRequestPart
+            responsibilityLookup = queryLocalCache nsSnap cache 1 (getNid senderNS)
+            thisNodeResponsible (FOUND _)   = True
+            thisNodeResponsible (FORWARD _) = False
+        -- check whether the joining node falls into our responsibility
+        if thisNodeResponsible responsibilityLookup
+        then do
+        -- if yes, adjust own predecessors/ successors and return those in a response
+           let
+             newPreds = take (kNeighbours nsSnap) . sortBy (flip localCompare) $ getNid senderNS:predecessors nsSnap
+             joinedNS = setPredecessors newPreds nsSnap
+             responsePayload = JoinResponsePayload {
+                joinSuccessors = successors joinedNS
+              , joinPredecessors = predecessors joinedNS
+              , joinCache = toRemoteCache cache
+                                                   }
+             joinResponse = Response {
+                 responseTo = requestID aRequestPart
+               , senderID = getNid joinedNS
+               , part = if Set.size msgSet == 1 then 1 else fromIntegral $ Set.size msgSet + 1
+               , isFinalPart = False
+               , action = Join
+               , payload = Just responsePayload
+                                     }
+           writeTVar nsSTM joinedNS
+           pure joinResponse
+        -- otherwise respond with empty payload
+        else pure Response {
+             responseTo = requestID aRequestPart
+           , senderID = getNid nsSnap
+           , part = if Set.size msgSet == 1 then 1 else fromIntegral $ Set.size msgSet + 1
+           , isFinalPart = False
+           , action = Join
+           , payload = Nothing
+                           }
+
+    pure $ serialiseMessage sendMessageSize responseMsg
+    -- TODO: notify service layer to copy over data now handled by the new joined node
 
 -- ....... request sending .......
 
@@ -249,13 +293,16 @@ requestJoin toJoinOn ownStateSTM =
                     ([], setPredecessors [] . setSuccessors [] $ ownState)
                     responses
                 -- sort successors and predecessors
-                newState = setSuccessors (sortBy localCompare $ successors joinedStateUnsorted) . setPredecessors (sortBy localCompare $ predecessors joinedStateUnsorted) $ joinedStateUnsorted
+                newState = setSuccessors (take (kNeighbours joinedStateUnsorted) . sortBy localCompare $ successors joinedStateUnsorted) . setPredecessors (take (kNeighbours joinedStateUnsorted) . sortBy (flip localCompare) $ predecessors joinedStateUnsorted) $ joinedStateUnsorted
             writeTVar ownStateSTM newState
             pure (cacheInsertQ, newState)
         -- execute the cache insertions
         mapM_ (\f -> f joinedState) cacheInsertQ
         if responses == Set.empty
            then pure . Left $ "join error: got no response from " <> show (getNid toJoinOn)
+           else if null (predecessors joinedState) && null (successors joinedState)
+                then pure $ Left "join error: no predecessors or successors"
+                -- successful join
                 else pure $ Right ownStateSTM
                                                                             )
         `catch` (\e -> pure . Left $ displayException (e :: IOException))

src/Hash2Pub/ProtocolTypes.hs

@@ -1,5 +1,7 @@
 module Hash2Pub.ProtocolTypes where
 
+import qualified Data.Map                as Map
+import           Data.Maybe              (mapMaybe)
 import qualified Data.Set                as Set
 import           Data.Time.Clock.POSIX   (POSIXTime)
 
@@ -83,11 +85,16 @@ data RemoteCacheEntry = RemoteCacheEntry RemoteNodeState POSIXTime
 instance Ord RemoteCacheEntry where
     (RemoteCacheEntry ns1 _) `compare` (RemoteCacheEntry ns2 _) = nid ns1 `compare` nid ns2
 
+-- | Extracts a 'RemoteCacheEntry' from the indirections of a 'CacheEntry', if it holds one
 toRemoteCacheEntry :: CacheEntry -> Maybe RemoteCacheEntry
 toRemoteCacheEntry (NodeEntry _ ns ts) = Just $ RemoteCacheEntry ns ts
 toRemoteCacheEntry (ProxyEntry _ (Just entry@NodeEntry{})) = toRemoteCacheEntry entry
 toRemoteCacheEntry _ = Nothing
 
+-- | a list of all entries of a 'NodeCache' as 'RemoteCacheEntry', useful for cache transfers
+toRemoteCache :: NodeCache -> [RemoteCacheEntry]
+toRemoteCache cache = mapMaybe toRemoteCacheEntry $ Map.elems cache
+
 -- | extract the 'NodeState' from a 'RemoteCacheEntry'
 remoteNode :: RemoteCacheEntry -> RemoteNodeState
 remoteNode (RemoteCacheEntry ns _) = ns