Change default response to QueryID for unjoined nodes

reason: allow unjoined nodes to find bootstrap node in local cache,
while always advertising itself to incoming requests for bootstrapping.

src/Hash2Pub/DHTProtocol.hs

@@ -90,7 +90,9 @@ import           Debug.Trace                    (trace)
 queryLocalCache :: LocalNodeState -> NodeCache -> Int -> NodeID -> QueryResponse
 queryLocalCache ownState nCache lBestNodes targetID
     -- as target ID falls between own ID and first predecessor, it is handled by this node
-      | targetID `isInOwnResponsibilitySlice` ownState = FOUND . toRemoteNodeState $ ownState
+    -- This only makes sense if the node is part of the DHT by having joined.
+    -- A default answer to nodes querying an unjoined node is provided by 'respondQueryID'.
+      | isJoined ownState && targetID `isInOwnResponsibilitySlice` ownState = FOUND . toRemoteNodeState $ ownState
     -- my interpretation: the "l best next hops" are the l-1 closest preceding nodes and
     -- the closest succeeding node (like with the p initiated parallel queries
       | otherwise = FORWARD $ closestSuccessor `Set.union` closestCachePredecessors (lBestNodes-1) targetID nCache
@@ -296,7 +298,11 @@ respondQueryID nsSTM msgSet = do
             cache <- readTVar $ nodeCacheSTM nsSnap
             let
                 responsePayload = QueryIDResponsePayload {
-                    queryResult = queryLocalCache nsSnap cache (fromIntegral $ queryLBestNodes senderPayload') (queryTargetID senderPayload')
+                    queryResult = if isJoined nsSnap
+                                     then queryLocalCache nsSnap cache (fromIntegral $ queryLBestNodes senderPayload') (queryTargetID senderPayload')
+                                     -- if not joined yet, attract responsibility for
+                                     -- all keys to make bootstrapping possible
+                                     else FOUND (toRemoteNodeState nsSnap)
                                                         }
                 queryResponseMsg = Response {
                     requestID = requestID aRequestPart

test/FediChordSpec.hs

@@ -132,10 +132,11 @@ spec = do
             cacheWith2Entries :: NodeCache
             cacheWith2Entries = addCacheEntryPure 10 (RemoteCacheEntry node5 10) (addCacheEntryPure 10 (RemoteCacheEntry node2 10) emptyCache)
             cacheWith4Entries = addCacheEntryPure 10 (RemoteCacheEntry node3 10) (addCacheEntryPure 10 (RemoteCacheEntry node4 10) cacheWith2Entries)
-        it "nodes not joined provide the default answer FOUND" $ do
+        it "unjoined nodes should never return themselfs" $ do
             exampleLocalNodeAsRemote <- toRemoteNodeState <$> exampleLocalNode
-            queryLocalCache <$> exampleLocalNode <*> pure emptyCache <*> pure 3 <*> pure (toNodeID 2^(9::Integer)+5) `shouldReturn` FOUND exampleLocalNodeAsRemote
+            queryLocalCache <$> exampleLocalNode <*> pure emptyCache <*> pure 3 <*> pure (toNodeID 2^(9::Integer)+5) `shouldReturn` FORWARD Set.empty
-            queryLocalCache <$> exampleLocalNode <*> pure cacheWith4Entries <*> pure 1 <*> pure (toNodeID 2342) `shouldReturn` FOUND exampleLocalNodeAsRemote
+            (FORWARD fwSet) <- queryLocalCache <$> exampleLocalNode <*> pure cacheWith4Entries <*> pure 1 <*> (getNid <$> exampleLocalNode)
+            remoteNode (head $ Set.elems fwSet) `shouldBe` node4
         it "joined nodes do not fall back to the default" $
             queryLocalCache <$> node1 <*> pure emptyCache <*> pure 1 <*> pure (toNodeID 3) `shouldReturn` FORWARD Set.empty
         it "works on a cache with less entries than needed" $ do
@@ -265,6 +266,17 @@ spec = do
             let startAt5 = serialiseMessage 600 (largeMessage {part = 5})
             Map.lookup 1 startAt5 `shouldBe` Nothing
             part <$> (deserialiseMessage . fromJust) (Map.lookup 5 startAt5) `shouldBe` Right 5
+    describe "join cache lookup" $
+        it "A bootstrap cache initialised with just one node returns that one." $ do
+            let
+                bootstrapNid = toNodeID 34804191837661041451755206127000721433747285589603756490902196113256157045194
+                bootstrapNode = setNid bootstrapNid exampleNodeState
+                bootstrapCache = addCacheEntryPure 10 (RemoteCacheEntry bootstrapNode 19) initCache
+                ownId = toNodeID 34804191837661041451755206127000721433707928516052624394829818586723613390165
+            ownNode <- setNid ownId <$> exampleLocalNode
+            let (FORWARD qResult) = queryLocalCache ownNode bootstrapCache 2 ownId
+            remoteNode (head $ Set.elems qResult) `shouldBe` bootstrapNode
+            
 
 
 -- some example data