add runtime flag for enabling k-choices or not

any value except "off" means on

contributes to #2

app/Main.hs

@@ -26,7 +26,7 @@ main = do
 
 readConfig :: IO (FediChordConf, ServiceConf)
 readConfig = do
-    confDomainString : ipString : portString : servicePortString : speedupString : remainingArgs <- getArgs
+    confDomainString : ipString : portString : servicePortString : speedupString : loadBalancingEnabled : remainingArgs <- getArgs
     -- allow starting the initial node without bootstrapping info to avoid
     -- waiting for timeout
     let
@@ -48,6 +48,7 @@ readConfig = do
           , confResponsePurgeAge = 60 / fromIntegral speedup
           , confRequestTimeout = 5 * 10^6 `div` speedup
           , confRequestRetries = 3
+          , confEnableKChoices = loadBalancingEnabled /= "off"
           }
         sConf = ServiceConf
           { confSubscriptionExpiryTime = 24*3600 / fromIntegral speedup

src/Hash2Pub/FediChord.hs

@@ -120,27 +120,32 @@ fediChordInit initConf serviceRunner = do
     -- 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 0
-    firstVSSTM <- newTVarIO firstVS
-    -- add vserver to list at RealNode
-    atomically . modifyTVar' realNodeSTM $ \rn -> rn { vservers = HMap.insert (getNid firstVS) firstVSSTM (vservers rn) }
-    -- try joining the DHT using one of the provided bootstrapping nodes
-    joinedState <- tryBootstrapJoining firstVSSTM
-    fediThreadsAsync <- either (\err -> do
-        -- handle unsuccessful join
+    fediThreadsAsync <- if confEnableKChoices initConf
+       then
+       -- TODO: k-choices way of joining
+       async (fediMainThreads serverSock realNodeSTM)
+       else do
+       -- without k-choices, just initialise a single vserver
+            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) }
+            -- try joining the DHT using one of the provided bootstrapping nodes
+            joinedState <- tryBootstrapJoining firstVSSTM
 
-        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 realNodeSTM)
-           )
-           (\joinedNS -> do
-        -- launch main eventloop with successfully joined state
-        putStrLn "successful join"
-        async (fediMainThreads serverSock realNodeSTM)
-           )
-        joinedState
+            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 realNodeSTM)
+                   )
+                   (\joinedNS -> do
+                -- launch main eventloop with successfully joined state
+                putStrLn "successful join"
+                async (fediMainThreads serverSock realNodeSTM)
+                   )
+                joinedState
     pure (fediThreadsAsync, realNodeSTM)
 
 -- | initialises the 'NodeState' for this local node.

src/Hash2Pub/FediChordTypes.hs

@@ -436,6 +436,8 @@ data FediChordConf = FediChordConf
     -- ^ how long to wait until response has arrived, in milliseconds
     , confRequestRetries            :: Int
     -- ^ how often re-sending a timed-out request can be retried
+    , confEnableKChoices            :: Bool
+    -- ^ whether to enable k-choices load balancing
     }
     deriving (Show, Eq)