Periodically contact bootstrap nodes for convergence sampling or joining
closes #56
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@ -50,4 +50,5 @@ readConfig = do
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, confDhtPort = read portString
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, confBootstrapNodes = [(bootstrapHost, read bootstrapPortString)]
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--, confStabiliseInterval = 60
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, confBootstrapSamplingInterval = 180
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}
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@ -82,6 +82,7 @@ import Network.Socket hiding (recv, recvFrom, send,
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sendTo)
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import Network.Socket.ByteString
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import Safe
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import System.Random (randomRIO)
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import Hash2Pub.DHTProtocol
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import Hash2Pub.FediChordTypes
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@ -142,30 +143,48 @@ fediChordBootstrapJoin :: LocalNodeStateSTM -- ^ the local 'NodeSta
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-> (String, PortNumber) -- ^ domain and port of a bootstrapping node
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-> IO (Either String LocalNodeStateSTM) -- ^ the joined 'NodeState' after a
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-- successful join, otherwise an error message
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fediChordBootstrapJoin nsSTM (joinHost, joinPort) =
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fediChordBootstrapJoin nsSTM bootstrapNode = do
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-- can be invoked multiple times with all known bootstrapping nodes until successfully joined
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bracket (mkSendSocket joinHost joinPort) close (\sock -> do
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putStrLn "BootstrapJoin"
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-- 1. get routed to placement of own ID until FOUND:
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-- Initialise an empty cache only with the responses from a bootstrapping node
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ns <- readTVarIO nsSTM
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bootstrapResponse <- sendRequestTo 5000 3 (lookupMessage (getNid ns) ns Nothing) sock
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if bootstrapResponse == Set.empty
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then pure . Left $ "Bootstrapping node " <> show joinHost <> " gave no response."
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else do
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now <- getPOSIXTime
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-- create new cache with all returned node responses
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let bootstrapCache =
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-- traverse response parts
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foldr' (\resp cacheAcc -> case queryResult <$> payload resp of
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Nothing -> cacheAcc
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Just (FOUND result1) -> addCacheEntryPure now (RemoteCacheEntry result1 now) cacheAcc
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Just (FORWARD resultset) -> foldr' (addCacheEntryPure now) cacheAcc resultset
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)
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initCache bootstrapResponse
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fediChordJoin bootstrapCache nsSTM
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)
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`catch` (\e -> pure . Left $ "Error at bootstrap joining: " <> displayException (e :: IOException))
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runExceptT $ do
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-- 1. get routed to the currently responsible node
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lookupResp <- liftIO $ bootstrapQueryId nsSTM bootstrapNode $ getNid ns
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currentlyResponsible <- liftEither lookupResp
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liftIO . putStrLn $ "Trying to join on " <> show (getNid currentlyResponsible)
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-- 2. then send a join to the currently responsible node
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joinResult <- liftIO $ requestJoin currentlyResponsible nsSTM
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liftEither joinResult
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-- Periodically lookup own ID through a random bootstrapping node to discover and merge separated DHT clusters.
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-- Unjoined try joining instead.
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convergenceSampleThread :: LocalNodeStateSTM -> IO ()
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convergenceSampleThread nsSTM = forever $ do
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nsSnap <- readTVarIO nsSTM
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parentNode <- readTVarIO $ parentRealNode nsSnap
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if isJoined nsSnap
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then
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runExceptT (do
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-- joined node: choose random node, do queryIDLoop, compare result with own responsibility
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let bss = bootstrapNodes parentNode
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randIndex <- liftIO $ randomRIO (0, length bss - 1)
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chosenNode <- maybe (throwError "invalid bootstrapping node index") pure $ atMay bss randIndex
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lookupResult <- liftIO $ bootstrapQueryId nsSTM chosenNode (getNid nsSnap)
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currentlyResponsible <- liftEither lookupResult
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if getNid currentlyResponsible /= getNid nsSnap
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-- if mismatch, stabilise on the result, else do nothing
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then do
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stabResult <- liftIO $ requestStabilise nsSnap currentlyResponsible
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(preds, succs) <- liftEither stabResult
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-- TODO: verify neighbours before adding, see #55
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liftIO . atomically $ do
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ns <- readTVar nsSTM
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writeTVar nsSTM $ addPredecessors preds ns
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else pure ()
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) >> pure ()
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-- unjoined node: try joining through all bootstrapping nodes
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else tryBootstrapJoining nsSTM >> pure ()
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let delaySecs = confBootstrapSamplingInterval . nodeConfig $ parentNode
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threadDelay $ delaySecs * 10^6
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-- | Try joining the DHT through any of the bootstrapping nodes until it succeeds.
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@ -185,19 +204,44 @@ tryBootstrapJoining nsSTM = do
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tryJoining [] = pure $ Left "Exhausted all bootstrap points for joining."
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-- | Look up a key just based on the responses of a single bootstrapping node.
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bootstrapQueryId :: LocalNodeStateSTM -> (String, PortNumber) -> NodeID -> IO (Either String RemoteNodeState)
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bootstrapQueryId nsSTM (bootstrapHost, bootstrapPort) targetID = do
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ns <- readTVarIO nsSTM
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bootstrapResponse <- bracket (mkSendSocket bootstrapHost bootstrapPort) close (
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-- Initialise an empty cache only with the responses from a bootstrapping node
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fmap Right . sendRequestTo 5000 3 (lookupMessage targetID ns Nothing)
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)
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`catch` (\e -> pure . Left $ "Error at bootstrap QueryId: " <> displayException (e :: IOException))
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-- | join a node to the DHT, using the provided cache snapshot for resolving the new
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case bootstrapResponse of
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Left err -> pure $ Left err
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Right resp
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| resp == Set.empty -> pure . Left $ "Bootstrapping node " <> show bootstrapHost <> " gave no response."
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| otherwise -> do
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now <- getPOSIXTime
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-- create new cache with all returned node responses
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let bootstrapCache =
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-- traverse response parts
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foldr' (\resp cacheAcc -> case queryResult <$> payload resp of
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Nothing -> cacheAcc
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Just (FOUND result1) -> addCacheEntryPure now (RemoteCacheEntry result1 now) cacheAcc
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Just (FORWARD resultset) -> foldr' (addCacheEntryPure now) cacheAcc resultset
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)
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initCache resp
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currentlyResponsible <- queryIdLookupLoop bootstrapCache ns 50 $ getNid ns
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pure $ Right currentlyResponsible
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-- | join a node to the DHT using the global node cache
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-- node's position.
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fediChordJoin :: NodeCache -- ^ a snapshot of the NodeCache to
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-- use for ID lookup
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-> LocalNodeStateSTM -- ^ the local 'NodeState'
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fediChordJoin :: LocalNodeStateSTM -- ^ the local 'NodeState'
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-> IO (Either String LocalNodeStateSTM) -- ^ the joined 'NodeState' after a
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-- successful join, otherwise an error message
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fediChordJoin cacheSnapshot nsSTM = do
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fediChordJoin nsSTM = do
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ns <- readTVarIO nsSTM
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-- get routed to the currently responsible node, based on the response
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-- from the bootstrapping node
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currentlyResponsible <- queryIdLookupLoop cacheSnapshot ns 50 $ getNid ns
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-- 1. get routed to the currently responsible node
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currentlyResponsible <- requestQueryID ns $ getNid ns
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putStrLn $ "Trying to join on " <> show (getNid currentlyResponsible)
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-- 2. then send a join to the currently responsible node
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joinResult <- requestJoin currentlyResponsible nsSTM
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@ -226,7 +270,7 @@ joinOnNewEntriesThread nsSTM = loop
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pure ()
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-- otherwise try joining
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FORWARD _ -> do
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joinResult <- fediChordJoin cache nsSTM
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joinResult <- fediChordJoin nsSTM
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either
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-- on join failure, sleep and retry
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-- TODO: make delay configurable
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@ -497,6 +541,7 @@ fediMainThreads sock nsSTM = do
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(fediMessageHandler sendQ recvQ nsSTM) $
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concurrently_ (stabiliseThread nsSTM) $
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concurrently_ (cacheVerifyThread nsSTM) $
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concurrently_ (convergenceSampleThread nsSTM) $
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concurrently_
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(sendThread sock sendQ)
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(recvThread sock recvQ)
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@ -589,10 +589,15 @@ byteStringToUInteger bs = sum $ parsedBytes 0 bs
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-- | configuration values used for initialising the FediChord DHT
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data FediChordConf = FediChordConf
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{ confDomain :: String
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-- ^ the domain/ hostname the node is reachable under
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, confIP :: HostAddress6
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-- ^ IP address of outgoing packets
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, confDhtPort :: Int
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-- ^ listening port for the FediChord DHT
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, confBootstrapNodes :: [(String, PortNumber)]
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--, confStabiliseInterval :: Int
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-- ^ list of potential bootstrapping nodes
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, confBootstrapSamplingInterval :: Int
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-- ^ pause between sampling the own ID through bootstrap nodes, in seconds
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}
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deriving (Show, Eq)
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