re-strucuture fediChordInit flow to also do the bootstrapping

app/Main.hs

@@ -18,29 +18,10 @@ main = do
     -- ToDo: parse and pass config
     -- probably use `tomland` for that
     (fConf, sConf) <- readConfig
-    -- TODO: first initialise 'RealNode', then the vservers
     -- ToDo: load persisted caches, bootstrapping nodes …
-    (serverSock, thisNode) <- fediChordInit fConf (runService sConf :: DHT d => d -> IO (PostService d))
+    (fediThreads, thisNode) <- fediChordInit fConf (runService sConf :: DHT d => d -> IO (PostService d))
-    -- currently no masking is necessary, as there is nothing to clean up
+    -- wait for all DHT threads to terminate, this keeps the main thread running
-    nodeCacheWriterThread <- forkIO $ nodeCacheWriter thisNode
+    wait fediThreads
-    -- try joining the DHT using one of the provided bootstrapping nodes
-    joinedState <- tryBootstrapJoining thisNode
-    either (\err -> do
-        -- handle unsuccessful join
-
-        putStrLn $ err <> " Error joining, start listening for incoming requests anyways"
-        print =<< readTVarIO thisNode
-        -- launch thread attempting to join on new cache entries
-        _ <- forkIO $ joinOnNewEntriesThread thisNode
-        wait =<< async (fediMainThreads serverSock thisNode)
-           )
-           (\joinedNS -> do
-        -- launch main eventloop with successfully joined state
-        putStrLn "successful join"
-        wait =<< async (fediMainThreads serverSock thisNode)
-           )
-        joinedState
-    pure ()
 
 
 readConfig :: IO (FediChordConf, ServiceConf)

src/Hash2Pub/FediChord.hs

@@ -98,38 +98,59 @@ import           Debug.Trace                   (trace)
 fediChordInit :: (Service s (RealNodeSTM s))
               => FediChordConf
               -> (RealNodeSTM s -> IO (s (RealNodeSTM s)))     -- ^ runner function for service
-              -> IO (Socket, RealNodeSTM s)
+              -> IO (Async (), RealNodeSTM s)
 fediChordInit initConf serviceRunner = do
     emptyLookupCache <- newTVarIO Map.empty
-    let realNode = RealNode {
+    cacheSTM <- newTVarIO initCache
-            vservers = HMap.empty
+    cacheQ <- atomically newTQueue
+    let realNode = RealNode
+          { vservers = HMap.empty
           , nodeConfig = initConf
           , bootstrapNodes = confBootstrapNodes initConf
           , lookupCacheSTM = emptyLookupCache
           , nodeService = undefined
+          , globalNodeCacheSTM = cacheSTM
+          , globalCacheWriteQueue = cacheQ
           }
     realNodeSTM <- newTVarIO realNode
+    serverSock <- mkServerSocket (confIP initConf) (fromIntegral $ confDhtPort initConf)
     -- launch service and set the reference in the RealNode
     serv <- serviceRunner realNodeSTM
     atomically . modifyTVar' realNodeSTM $ \rn -> rn { nodeService = serv }
+    -- prepare for joining: start node cache writer thread
+    -- currently no masking is necessary, as there is nothing to clean up
+    nodeCacheWriterThread <- forkIO $ nodeCacheWriter realNodeSTM
     -- TODO: k-choices way of joining, so far just initialise a single vserver
-    firstVS <- nodeStateInit realNodeSTM
+    firstVS <- nodeStateInit realNodeSTM 0
     firstVSSTM <- newTVarIO firstVS
     -- add vserver to list at RealNode
     atomically . modifyTVar' realNodeSTM $ \rn -> rn { vservers = HMap.insert (getNid firstVS) firstVSSTM (vservers rn) }
-    serverSock <- mkServerSocket (confIP initConf) (fromIntegral $ confDhtPort initConf)
+    -- try joining the DHT using one of the provided bootstrapping nodes
-    pure (serverSock, realNodeSTM)
+    joinedState <- tryBootstrapJoining firstVSSTM
+    fediThreadsAsync <- either (\err -> do
+        -- handle unsuccessful join
+
+        putStrLn $ err <> " Error joining, start listening for incoming requests anyways"
+        -- launch thread attempting to join on new cache entries
+        _ <- forkIO $ joinOnNewEntriesThread firstVSSTM
+        async (fediMainThreads serverSock firstVSSTM)
+           )
+           (\joinedNS -> do
+        -- launch main eventloop with successfully joined state
+        putStrLn "successful join"
+        async (fediMainThreads serverSock firstVSSTM)
+           )
+        joinedState
+    pure (fediThreadsAsync, realNodeSTM)
 
 -- | initialises the 'NodeState' for this local node.
 -- Separated from 'fediChordInit' to be usable in tests.
-nodeStateInit :: Service s (RealNodeSTM s) => RealNodeSTM s -> IO (LocalNodeState s)
+nodeStateInit :: Service s (RealNodeSTM s) => RealNodeSTM s -> Integer -> IO (LocalNodeState s)
-nodeStateInit realNodeSTM = do
+nodeStateInit realNodeSTM vsID' = do
     realNode <- readTVarIO realNodeSTM
-    cacheSTM <- newTVarIO initCache
-    q <- atomically newTQueue
     let
         conf = nodeConfig realNode
-        vsID = 0
+        vsID = vsID'
         containedState = RemoteNodeState {
             domain = confDomain conf
           , ipAddr = confIP conf
@@ -140,8 +161,8 @@ nodeStateInit realNodeSTM = do
                                           }
         initialState = LocalNodeState {
             nodeState = containedState
-          , nodeCacheSTM = cacheSTM
+          , nodeCacheSTM = globalNodeCacheSTM realNode
-          , cacheWriteQueue = q
+          , cacheWriteQueue = globalCacheWriteQueue realNode
           , successors = []
           , predecessors = []
           , kNeighbours = 3
@@ -336,12 +357,12 @@ joinOnNewEntriesThread nsSTM = loop
 
 -- | cache updater thread that waits for incoming NodeCache update instructions on
 -- the node's cacheWriteQueue and then modifies the NodeCache as the single writer.
-nodeCacheWriter :: LocalNodeStateSTM s -> IO ()
+nodeCacheWriter :: RealNodeSTM s -> IO ()
-nodeCacheWriter nsSTM =
+nodeCacheWriter nodeSTM = do
+    node <- readTVarIO nodeSTM
     forever $ atomically $ do
-        ns <- readTVar nsSTM
+        cacheModifier <- readTQueue $ globalCacheWriteQueue node
-        cacheModifier <- readTQueue $ cacheWriteQueue ns
+        modifyTVar' (globalNodeCacheSTM node) cacheModifier
-        modifyTVar' (nodeCacheSTM ns) cacheModifier
 
 
 -- | Periodically iterate through cache, clean up expired entries and verify unverified ones

src/Hash2Pub/FediChordTypes.hs

@@ -161,6 +161,13 @@ data RealNode s = RealNode
     -- ^ nodes to be used as bootstrapping points, new ones learned during operation
     , lookupCacheSTM :: TVar LookupCache
     -- ^ a global cache of looked up keys and their associated nodes
+    , globalNodeCacheSTM :: TVar NodeCache
+    -- ^ EpiChord node cache with expiry times for nodes.
+    -- Shared between all vservers, each 'LocalNodeState' holds a reference to
+    -- the same TVar for avoiding unnecessary reads of parent node
+    , globalCacheWriteQueue     :: TQueue (NodeCache -> NodeCache)
+    -- ^ cache updates are not written directly to the  'globalNodeCacheSTM'
+    -- but queued and processed by a single thread
     , nodeService    :: s (RealNodeSTM s)
     }
 
@@ -190,9 +197,9 @@ data LocalNodeState s = LocalNodeState
     { nodeState           :: RemoteNodeState
     -- ^ represents common data present both in remote and local node representations
     , nodeCacheSTM        :: TVar NodeCache
-    -- ^ EpiChord node cache with expiry times for nodes
+    -- ^ reference to the 'globalNodeCacheSTM'
     , cacheWriteQueue     :: TQueue (NodeCache -> NodeCache)
-    -- ^ cache updates are not written directly to the  'nodeCache' but queued and
+    -- ^ reference to the 'globalCacheWriteQueue
     , successors          :: [RemoteNodeState] -- could be a set instead as these are ordered as well
     -- ^ successor nodes in ascending order by distance
     , predecessors        :: [RemoteNodeState]