start implementing k-choices rebalancing, considering 1 VS each run

only loop implemented, rebalancing not implemented

src/Hash2Pub/FediChord.hs

@@ -322,6 +322,34 @@ kChoicesDepartureCost remainingOwnLoad ownCap thisSegmentLoad segment =
   + abs (remainingOwnLoad + thisSegmentLoad) / ownCap
   - abs (segmentOwnerRemainingLoadTarget segment) / segmentOwnerCapacity segment
 
+
+kChoicesRebalanceThread :: (Service s (RealNodeSTM s)) => RealNodeSTM s -> IO ()
+kChoicesRebalanceThread nodeSTM = (confKChoicesRebalanceInterval . nodeConfig <$> readTVarIO nodeSTM) >>= rebalanceVS 0
+  where
+      rebalanceVS :: NodeID -> Int -> IO ()
+      rebalanceVS startAt interval = do
+          threadDelay interval
+          (vsToRebalance', serv) <- atomically $ do
+              node <- readTVar nodeSTM
+              pure (rMapLookupPred 0 (vservers node), nodeService node)
+          maybe
+            -- wait and retry if no active VS available
+            (rebalanceVS startAt interval)
+            (\(vsNid, vsSTM) -> do
+              vs <- readTVarIO vsSTM
+              -- query neighbour node(s) load
+              -- query own load
+              -- calculate departure cost
+              -- if deciding to re-balance, first leave and then join
+              -- loop
+              rebalanceVS vsNid interval
+              )
+              vsToRebalance'
+
+
+          -- placeholder
+          pure ()
+
 -- | Join a new node into the DHT, using a provided bootstrap node as initial cache seed
 -- for resolving the new node's position.
 fediChordBootstrapJoin :: Service s (RealNodeSTM s)