Merge branch 'fix_networking': fix some DHT joins and crashes

several major flaws in the basic DHT communication had been discovered,
see individual commits for details

Hash2Pub.cabal

@@ -47,7 +47,7 @@ extra-source-files:  CHANGELOG.md
 
 common deps
   build-depends:       base ^>=4.12.0.0, containers ^>=0.6.0.1, bytestring, utf8-string ^>=1.0.1.1, network ^>=2.8.0.1, time ^>=1.8.0.2, cmdargs ^>= 0.10, cryptonite ^>= 0.25, memory, async, stm, asn1-encoding, asn1-types, asn1-parse, publicsuffix, network-byte-order, safe, iproute, mtl, random, servant, servant-server, servant-client, warp, text, unordered-containers, hashable, unicode-transforms, http-client, http-types, unbounded-delays
-  ghc-options:         -Wall
+  ghc-options:         -Wall -Wpartial-fields
 
 
 

app/Experiment.hs

@@ -1,16 +1,16 @@
-{-# LANGUAGE OverloadedStrings     #-}
+{-# LANGUAGE OverloadedStrings #-}
 
 module Main where
 
-import System.Random
-import Control.Concurrent
-import Control.Monad (forM_)
-import Control.Monad.State.Class
-import Control.Monad.State.Strict (evalStateT)
-import Control.Monad.IO.Class
-import qualified Network.HTTP.Client           as HTTP
+import           Control.Concurrent
+import           Control.Monad              (forM_)
+import           Control.Monad.IO.Class
+import           Control.Monad.State.Class
+import           Control.Monad.State.Strict (evalStateT)
+import qualified Network.HTTP.Client        as HTTP
+import           System.Random
 
-import Hash2Pub.PostService     (clientPublishPost, Hashtag)
+import           Hash2Pub.PostService       (Hashtag, clientPublishPost)
 
 -- placeholder post data definition
 

src/Hash2Pub/DHTProtocol.hs

@@ -49,9 +49,11 @@ import           Control.Concurrent.STM.TQueue
 import           Control.Concurrent.STM.TVar
 import           Control.Exception
 import           Control.Monad                  (foldM, forM, forM_, void, when)
+import           Control.Monad.Except           (MonadError (..), runExceptT)
+import           Control.Monad.IO.Class         (MonadIO (..))
 import qualified Data.ByteString                as BS
 import           Data.Either                    (rights)
-import           Data.Foldable                  (foldl', foldr')
+import           Data.Foldable                  (foldl', foldr', foldrM)
 import           Data.Functor.Identity
 import           Data.IP                        (IPv6, fromHostAddress6,
                                                  toHostAddress6)
@@ -514,28 +516,28 @@ requestJoin toJoinOn ownStateSTM = do
                     ([], Set.empty, Set.empty)
                     responses
                 -- sort, slice and set the accumulated successors and predecessors
-                newState = setSuccessors (Set.elems succAccSet) . setPredecessors (Set.elems predAccSet) $ stateSnap
+                -- the contacted node itself is a successor as well and, with few
+                -- nodes, can be a predecessor as well
+                newState = setSuccessors (toRemoteNodeState toJoinOn:Set.elems succAccSet) . setPredecessors (toRemoteNodeState toJoinOn:Set.elems predAccSet) $ stateSnap
             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 do
-                    -- wait for migration data to be completely received
-                    waitForMigrationFrom (nodeService prn) (getNid ownState)
-                    pure $ Right ownStateSTM
+           else do
+                -- wait for migration data to be completely received
+                waitForMigrationFrom (nodeService prn) (getNid toJoinOn)
+                pure $ Right ownStateSTM
                                    )
         `catch` (\e -> pure . Left $ displayException (e :: IOException))
 
 
 -- | Send a 'QueryID' 'Request' for getting the node that handles a certain key ID.
-requestQueryID :: LocalNodeState s        -- ^ NodeState of the querying node
+requestQueryID :: (MonadIO m, MonadError String m)
+               => LocalNodeState s        -- ^ NodeState of the querying node
                -> NodeID                -- ^ target key ID to look up
-               -> IO RemoteNodeState    -- ^ the node responsible for handling that key
+               -> m RemoteNodeState    -- ^ the node responsible for handling that key
 -- 1. do a local lookup for the l closest nodes
 -- 2. create l sockets
 -- 3. send a message async concurrently to all l nodes
@@ -543,23 +545,23 @@ requestQueryID :: LocalNodeState s        -- ^ NodeState of the querying node
 -- 5. repeat until FOUND (problem: new entries not necessarily already in cache, explicitly compare with closer results)
 -- TODO: deal with lookup failures
 requestQueryID ns targetID = do
-    firstCacheSnapshot <- readTVarIO . nodeCacheSTM $ ns
+    firstCacheSnapshot <- liftIO . readTVarIO . nodeCacheSTM $ ns
     -- TODO: make maxAttempts configurable
     queryIdLookupLoop firstCacheSnapshot ns 50 targetID
 
 -- | like 'requestQueryID, but allows passing of a custom cache, e.g. for joining
-queryIdLookupLoop :: NodeCache -> LocalNodeState s -> Int -> NodeID -> IO RemoteNodeState
+queryIdLookupLoop :: (MonadIO m, MonadError String m) => NodeCache -> LocalNodeState s -> Int -> NodeID -> m RemoteNodeState
 -- return node itself as default fallback value against infinite recursion.
 -- TODO: consider using an Either instead of a default value
-queryIdLookupLoop _ ns 0 _ = pure $ toRemoteNodeState ns
+queryIdLookupLoop _ ns 0 _ = throwError "exhausted maximum lookup attempts"
 queryIdLookupLoop cacheSnapshot ns maxAttempts targetID = do
     let localResult = queryLocalCache ns cacheSnapshot (lNumBestNodes ns) targetID
     -- FOUND can only be returned if targetID is owned by local node
     case localResult of
       FOUND thisNode -> pure thisNode
       FORWARD nodeSet -> do
-          responseEntries <- sendQueryIdMessages targetID ns Nothing (remoteNode <$> Set.elems nodeSet)
-          now <- getPOSIXTime
+          responseEntries <- liftIO $ sendQueryIdMessages targetID ns Nothing (remoteNode <$> Set.elems nodeSet)
+          now <- liftIO getPOSIXTime
           -- check for a FOUND and return it
           case responseEntries of
             FOUND foundNode -> pure foundNode
@@ -593,8 +595,10 @@ sendQueryIdMessages targetID ns lParam targets = do
           -- insert new cache entries both into global cache as well as return accumulated QueryResponses for further processing
           now <- getPOSIXTime
           -- collect cache entries from all responses
-          foldM (\acc resp -> do
-            let entrySet = case queryResult <$> payload resp of
+          foldrM (\resp acc -> do
+            let
+                responseResult = queryResult <$> payload resp
+                entrySet = case responseResult of
                              Just (FOUND result1) -> Set.singleton (RemoteCacheEntry result1 now)
                              Just (FORWARD resultset) -> resultset
                              _ -> Set.empty
@@ -604,10 +608,15 @@ sendQueryIdMessages targetID ns lParam targets = do
             -- return accumulated QueryResult
             pure $ case acc of
               -- once a FOUND as been encountered, return this as a result
-              isFound@FOUND{} -> isFound
-              FORWARD accSet  -> FORWARD $ entrySet `Set.union` accSet
+              FOUND{} -> acc
+              FORWARD accSet
+                | maybe False isFound responseResult -> fromJust responseResult
+                | otherwise -> FORWARD $ entrySet `Set.union` accSet
 
                             ) (FORWARD Set.empty) responses
+  where
+      isFound FOUND{} = True
+      isFound _       = False
 
 -- | Create a QueryID message to be supplied to 'sendRequestTo'
 lookupMessage :: Integral i
@@ -649,8 +658,7 @@ requestStabilise ns neighbour = do
                                                       )
                                                       ([],[]) respSet
             -- update successfully responded neighbour in cache
-            now <- getPOSIXTime
-            maybe (pure ()) (\p -> queueAddEntries (Identity $ RemoteCacheEntry (sender p) now) ns) $ headMay (Set.elems respSet)
+            maybe (pure ()) (\p -> queueUpdateVerifieds (Identity $ senderID p) ns) $ headMay (Set.elems respSet)
             pure $ if null responsePreds && null responseSuccs
                       then Left "no neighbours returned"
                       else Right (responsePreds, responseSuccs)
@@ -766,14 +774,14 @@ sendRequestToWithParams timeoutMillis numAttempts msgIncomplete sock = do
                -> Map.Map Integer BS.ByteString     -- ^ the remaining unacked request parts
                -> IO ()
     sendAndAck responseQueue sock' remainingSends = do
-        sendMany sock $ Map.elems remainingSends
+        sendMany sock' $ Map.elems remainingSends
         -- if all requests have been acked/ responded to, return prematurely
         recvLoop sock' responseQueue remainingSends Set.empty Nothing
     recvLoop :: Socket
              -> TBQueue FediChordMessage          -- ^ the queue for putting in the received responses
              -> Map.Map Integer BS.ByteString       -- ^ the remaining unacked request parts
              -> Set.Set Integer                     -- ^ already received response part numbers
-               -> Maybe Integer                     -- ^ total number of response parts if already known
+             -> Maybe Integer                     -- ^ total number of response parts if already known
              -> IO ()
     recvLoop sock' responseQueue remainingSends' receivedPartNums totalParts = do
         -- 65535 is maximum length of UDP packets, as long as
@@ -786,10 +794,11 @@ sendRequestToWithParams timeoutMillis numAttempts msgIncomplete sock = do
                 newTotalParts = if isFinalPart msg then Just (part msg) else totalParts
                 newRemaining = Map.delete (part msg) remainingSends'
                 newReceivedParts = Set.insert (part msg) receivedPartNums
-              if Map.null newRemaining && maybe False (\p -> Set.size receivedPartNums == fromIntegral p) newTotalParts
+              if  Map.null newRemaining && maybe False (\p -> Set.size newReceivedParts == fromIntegral p) newTotalParts
                  then pure ()
-                 else recvLoop sock' responseQueue newRemaining receivedPartNums newTotalParts
+                 else recvLoop sock' responseQueue newRemaining newReceivedParts newTotalParts
           -- drop errors and invalid messages
+          Right Request{} -> pure ()    -- expecting a response, not a request
           Left _ -> recvLoop sock' responseQueue remainingSends' receivedPartNums totalParts
 
 
@@ -816,6 +825,18 @@ queueDeleteEntry :: NodeID
                  -> IO ()
 queueDeleteEntry toDelete = queueDeleteEntries $ Identity toDelete
 
+
+-- | enqueue the timestamp update and verification marking of an entry in the
+-- global 'NodeCache'.
+queueUpdateVerifieds :: Foldable c
+                     => c NodeID
+                     -> LocalNodeState s
+                     -> IO ()
+queueUpdateVerifieds nIds ns = do
+    now <- getPOSIXTime
+    forM_ nIds $ \nid' -> atomically $ writeTQueue (cacheWriteQueue ns) $
+        markCacheEntryAsVerified (Just now) nid'
+
 -- | retry an IO action at most *i* times until it delivers a result
 attempts :: Int             -- ^ number of retries *i*
          -> IO (Maybe a)    -- ^ action to retry

src/Hash2Pub/FediChord.hs

@@ -166,6 +166,7 @@ fediChordBootstrapJoin nsSTM bootstrapNode = do
         currentlyResponsible <- liftEither lookupResp
         liftIO . putStrLn $ "Trying to join on " <> show (getNid currentlyResponsible)
         -- 2. then send a join to the currently responsible node
+        liftIO $ putStrLn "send a bootstrap Join"
         joinResult <- liftIO $ requestJoin currentlyResponsible nsSTM
         liftEither joinResult
 
@@ -244,26 +245,24 @@ bootstrapQueryId nsSTM (bootstrapHost, bootstrapPort) targetID = do
                            Just (FORWARD resultset) -> foldr' (addCacheEntryPure now) cacheAcc resultset
                               )
                            initCache resp
-               currentlyResponsible <- queryIdLookupLoop bootstrapCache ns 50 $ getNid ns
-               pure $ Right currentlyResponsible
+               currentlyResponsible <- runExceptT $ queryIdLookupLoop bootstrapCache ns 50 $ getNid ns
+               pure currentlyResponsible
 
 
 -- | join a node to the DHT using the global node cache
 -- node's position.
-fediChordVserverJoin :: Service s (RealNodeSTM s)
+fediChordVserverJoin :: (MonadError String m, MonadIO m, Service s (RealNodeSTM s))
                      => LocalNodeStateSTM s                    -- ^ the local 'NodeState'
-                     -> IO (Either String (LocalNodeStateSTM s))  -- ^ the joined 'NodeState' after a
+                     -> m (LocalNodeStateSTM s)  -- ^ the joined 'NodeState' after a
                                                     -- successful join, otherwise an error message
 fediChordVserverJoin nsSTM = do
-    ns <- readTVarIO nsSTM
+    ns <- liftIO $ readTVarIO nsSTM
     -- 1. get routed to the currently responsible node
     currentlyResponsible <- requestQueryID ns $ getNid ns
-    putStrLn $ "Trying to join on " <> show (getNid currentlyResponsible)
+    liftIO . putStrLn $ "Trying to join on " <> show (getNid currentlyResponsible)
     -- 2. then send a join to the currently responsible node
-    joinResult <- requestJoin currentlyResponsible nsSTM
-    case joinResult of
-      Left err       -> pure . Left $ "Error joining on " <> err
-      Right joinedNS -> pure . Right $ joinedNS
+    joinResult <- liftIO $ requestJoin currentlyResponsible nsSTM
+    liftEither joinResult
 
 fediChordVserverLeave :: (MonadError String m, MonadIO m, Service s (RealNodeSTM s)) => LocalNodeState s -> m ()
 fediChordVserverLeave ns = do
@@ -323,7 +322,7 @@ joinOnNewEntriesThread nsSTM = loop
               pure ()
           -- otherwise try joining
           FORWARD _ -> do
-              joinResult <- fediChordVserverJoin nsSTM
+              joinResult <- runExceptT $ fediChordVserverJoin nsSTM
               either
                 -- on join failure, sleep and retry
                 -- TODO: make delay configurable
@@ -504,18 +503,26 @@ stabiliseThread nsSTM = forever $ do
     -- try looking up additional neighbours if list too short
     forM_ [(length $ predecessors updatedNs)..(kNeighbours updatedNs)] (\_ -> do
         ns' <- readTVarIO nsSTM
-        nextEntry <- requestQueryID ns' $ pred . getNid $ lastDef (toRemoteNodeState ns') (predecessors ns')
-        atomically $ do
-            latestNs <- readTVar nsSTM
-            writeTVar nsSTM $ addPredecessors [nextEntry] latestNs
+        nextEntry <- runExceptT . requestQueryID ns' $ pred . getNid $ lastDef (toRemoteNodeState ns') (predecessors ns')
+        either
+            (const $ pure ())
+            (\entry -> atomically $ do
+                latestNs <- readTVar nsSTM
+                writeTVar nsSTM $ addPredecessors [entry] latestNs
+            )
+            nextEntry
                                                                        )
 
     forM_ [(length $ successors updatedNs)..(kNeighbours updatedNs)] (\_ -> do
         ns' <- readTVarIO nsSTM
-        nextEntry <- requestQueryID ns' $ succ . getNid $ lastDef (toRemoteNodeState ns') (successors ns')
-        atomically $ do
-            latestNs <- readTVar nsSTM
-            writeTVar nsSTM $ addSuccessors [nextEntry] latestNs
+        nextEntry <- runExceptT . requestQueryID ns' $ succ . getNid $ lastDef (toRemoteNodeState ns') (successors ns')
+        either
+            (const $ pure ())
+            (\entry -> atomically $ do
+                latestNs <- readTVar nsSTM
+                writeTVar nsSTM $ addSuccessors [entry] latestNs
+            )
+            nextEntry
                                                                      )
 
     newNs <- readTVarIO nsSTM
@@ -638,7 +645,7 @@ requestMapPurge :: MVar RequestMap -> IO ()
 requestMapPurge mapVar = forever $ do
     rMapState <- takeMVar mapVar
     now <- getPOSIXTime
-    putMVar mapVar $ Map.filter (\entry@(RequestMapEntry _ _ ts)  ->
+    putMVar mapVar $ Map.filter (\(RequestMapEntry _ _ ts)  ->
         now - ts < responsePurgeAge
                                 ) rMapState
     threadDelay $ round responsePurgeAge * 2 * 10^6
@@ -757,7 +764,7 @@ getKeyResponsibility nodeSTM lookupKey = do
 -- new entry.
 -- If no vserver is active in the DHT, 'Nothing' is returned.
 updateLookupCache :: RealNodeSTM s -> NodeID -> IO (Maybe (String, PortNumber))
-updateLookupCache nodeSTM lookupKey = do
+updateLookupCache nodeSTM keyToLookup = do
     (node, lookupSource) <- atomically $ do
         node <- readTVar nodeSTM
         let firstVs = headMay (vservers node)
@@ -767,18 +774,25 @@ updateLookupCache nodeSTM lookupKey = do
         pure (node, lookupSource)
     maybe (do
         -- if no local node available, delete cache entry and return Nothing
-        atomically $ modifyTVar' (lookupCacheSTM node) $ Map.delete lookupKey
+        atomically $ modifyTVar' (lookupCacheSTM node) $ Map.delete keyToLookup
         pure Nothing
           )
           (\n -> do
         -- start a lookup from the node, update the cache with the lookup result and return it
-        newResponsible <- requestQueryID n lookupKey
-        let newEntry = (getDomain newResponsible, getServicePort newResponsible)
-        now <- getPOSIXTime
-        -- atomic update against lost updates
-        atomically $ modifyTVar' (lookupCacheSTM node) $
-            Map.insert lookupKey (CacheEntry False newEntry now)
-        pure $ Just newEntry
+        -- TODO: better retry management, because having no vserver joined yet should
+        -- be treated differently than other reasons for not getting a result.
+        newResponsible <- runExceptT $ requestQueryID n keyToLookup
+        either
+            (const $ pure Nothing)
+            (\result -> do
+                let newEntry = (getDomain result, getServicePort result)
+                now <- getPOSIXTime
+                -- atomic update against lost updates
+                atomically $ modifyTVar' (lookupCacheSTM node) $
+                    Map.insert keyToLookup (CacheEntry False newEntry now)
+                pure $ Just newEntry
+            )
+            newResponsible
            ) lookupSource
 
 

src/Hash2Pub/PostService.hs

@@ -10,37 +10,30 @@ module Hash2Pub.PostService where
 
 import           Control.Concurrent
 import           Control.Concurrent.Async
-import           Control.Concurrent.MVar
 import           Control.Concurrent.STM
-import           Control.Concurrent.STM.TChan
-import           Control.Concurrent.STM.TChan
-import           Control.Concurrent.STM.TQueue
-import           Control.Concurrent.STM.TVar
-import           Control.Exception             (Exception (..), try)
-import           Control.Monad                 (foldM, forM, forM_, forever, when, void)
-import           Control.Monad.IO.Class        (liftIO)
-import           Control.Monad.STM
+import           Control.Exception         (Exception (..), try)
+import           Control.Monad             (foldM, forM, forM_, forever, void,
+                                            when)
+import           Control.Monad.IO.Class    (liftIO)
 import           Data.Bifunctor
-import qualified Data.ByteString.Lazy.UTF8     as BSUL
-import qualified Data.ByteString.UTF8          as BSU
-import qualified Data.HashMap.Strict           as HMap
-import qualified Data.HashSet                  as HSet
-import           Data.Maybe                    (fromMaybe, isJust)
-import           Data.String                   (fromString)
-import qualified Data.Text.Lazy                as Txt
-import           Data.Text.Normalize           (NormalizationMode (NFC),
-                                                normalize)
+import qualified Data.ByteString.Lazy.UTF8 as BSUL
+import qualified Data.ByteString.UTF8      as BSU
+import qualified Data.HashMap.Strict       as HMap
+import qualified Data.HashSet              as HSet
+import           Data.Maybe                (fromMaybe, isJust)
+import           Data.String               (fromString)
+import qualified Data.Text.Lazy            as Txt
+import           Data.Text.Normalize       (NormalizationMode (NFC), normalize)
 import           Data.Time.Clock.POSIX
-import           Data.Typeable                 (Typeable)
-import qualified Network.HTTP.Client           as HTTP
-import qualified Network.HTTP.Types            as HTTPT
+import           Data.Typeable             (Typeable)
+import qualified Network.HTTP.Client       as HTTP
+import qualified Network.HTTP.Types        as HTTPT
 import           System.Random
-import           Text.Read                     (readEither)
+import           Text.Read                 (readEither)
 
-import qualified Network.Wai.Handler.Warp      as Warp
+import qualified Network.Wai.Handler.Warp  as Warp
 import           Servant
 import           Servant.Client
-import           Servant.Server
 
 import           Hash2Pub.FediChordTypes
 import           Hash2Pub.RingMap
@@ -355,7 +348,7 @@ clientDeliverSubscriptions :: PostService d
                            -> (String, Int)     -- ^ hostname and port of instance to deliver to
                            -> IO (Either String ())     -- Either signals success or failure
 clientDeliverSubscriptions serv fromNode fromKey toKey (toHost, toPort) = do
-    -- collect tag intearval
+    -- collect tag interval
     intervalTags <- takeRMapSuccessorsFromTo fromKey toKey <$> readTVarIO (subscribers serv)
     -- returns a [ (TagSubscribersSTM, TChan PostID, Hashtag) ]
     -- extract subscribers and posts