Kademlia Contact Removal

- Contact removal now working well, we only do removal when we need to get in touch with the contact for some reason.
- Replacement cache is now setup

src/kademlia/operation/ContentLookupOperation.java

@@ -284,9 +284,9 @@ public class ContentLookupOperation implements Operation, Receiver
             throw new UnknownMessageException("Unknown comm: " + comm);
         }
 
-        /* Mark this node as failed */
+        /* Mark this node as failed and inform the routing table that it's unresponsive */
         this.nodes.put(n, FAILED);
-        this.localNode.getRoutingTable().remove(n);
+        this.localNode.getRoutingTable().setUnresponsiveContact(n);
         this.messagesTransiting.remove(comm);
 
         this.askNodesorFinish();

src/kademlia/operation/NodeLookupOperation.java

@@ -303,9 +303,9 @@ public class NodeLookupOperation implements Operation, Receiver
             throw new UnknownMessageException("Unknown comm: " + comm);
         }
 
-        /* Mark this node as failed */
+        /* Mark this node as failed and inform the routing table that it is unresponsive */
         this.nodes.put(n, FAILED);
-        this.localNode.getRoutingTable().remove(n);
+        this.localNode.getRoutingTable().setUnresponsiveContact(n);
         this.messagesTransiting.remove(comm);
         
         this.askNodesorFinish();

src/kademlia/routing/Bucket.java

@@ -48,15 +48,19 @@ public interface Bucket
      * Remove a contact from this bucket
      *
      * @param c The contact to remove
+     *
+     * @return Boolean whether the removal was successful.
      */
-    public void removeContact(Contact c);
+    public boolean removeContact(Contact c);
 
     /**
      * Remove the contact object related to a node from this bucket
      *
      * @param n The node of the contact to remove
+     *
+     * @return Boolean whether the removal was successful.
      */
-    public void removeNode(Node n);
+    public boolean removeNode(Node n);
 
     /**
      * Counts the number of contacts in this bucket.

src/kademlia/routing/KadBucket.java

@@ -2,8 +2,8 @@ package kademlia.routing;
 
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Map;
 import java.util.TreeMap;
+import kademlia.core.KadConfiguration;
 import kademlia.node.Node;
 
 /**
@@ -19,10 +19,12 @@ public class KadBucket implements Bucket
     private final int depth;
 
     /* Contacts stored in this routing table */
-    private final Map<Contact, Contact> contacts;
+    private final TreeMap<Contact, Contact> contacts;
 
     /* A set of last seen contacts that can replace any current contact that is unresponsive */
-    private final Map<Contact, Contact> replacementCache;
+    private final TreeMap<Contact, Contact> replacementCache;
+
+    private KadConfiguration config;
 
     
     {
@@ -31,17 +33,18 @@ public class KadBucket implements Bucket
     }
 
     /**
-     * @param depth How deep in the routing tree is this bucket
+     * @param depth  How deep in the routing tree is this bucket
+     * @param config
      */
-    public KadBucket(int depth)
+    public KadBucket(int depth, KadConfiguration config)
     {
         this.depth = depth;
+        this.config = config;
     }
 
     @Override
     public void insert(Contact c)
     {
-        /* @todo Check if the bucket is filled already and handle the situation */
         if (this.contacts.containsKey(c))
         {
             /**
@@ -54,7 +57,16 @@ public class KadBucket implements Bucket
         }
         else
         {
-            contacts.put(c, c);
+            /* If the bucket is filled, we put the contacts in the replacement cache */
+            if (contacts.size() >= this.config.k())
+            {
+                /* Bucket is filled, place this contact in the replacement cache */
+                this.insertIntoCache(c);
+            }
+            else
+            {
+                contacts.put(c, c);
+            }
         }
     }
 
@@ -77,15 +89,31 @@ public class KadBucket implements Bucket
     }
 
     @Override
-    public void removeContact(Contact c)
+    public boolean removeContact(Contact c)
     {
+        /* If the contact does not exist, then we failed to remove it */
+        if (!this.contacts.containsKey(c))
+        {
+            return false;
+        }
+
         this.contacts.remove(c);
+
+        /* If there are replacement contacts in the replacement cache, lets put them into the bucket */
+        if (!this.replacementCache.isEmpty())
+        {
+            Contact replacement = this.replacementCache.firstKey();
+            this.contacts.put(replacement, replacement);
+            this.replacementCache.remove(replacement);
+        }
+
+        return true;
     }
 
     @Override
-    public void removeNode(Node n)
+    public boolean removeNode(Node n)
     {
-        this.removeContact(new Contact(n));
+        return this.removeContact(new Contact(n));
     }
 
     @Override
@@ -106,6 +134,26 @@ public class KadBucket implements Bucket
         return (this.contacts.isEmpty()) ? new ArrayList<>() : new ArrayList<>(this.contacts.values());
     }
 
+    /**
+     * When the bucket is filled, we keep extra contacts in the replacement cache.
+     */
+    private void insertIntoCache(Contact c)
+    {
+        /* Just return if this contact is already in our replacement cache */
+        if (this.replacementCache.containsKey(c))
+        {
+            return;
+        }
+        
+        /* if our cache is filled, we remove the least recently seen contact */
+        if (this.replacementCache.size() > this.config.k())
+        {
+            this.replacementCache.remove(this.replacementCache.lastKey());
+        }
+
+        this.replacementCache.put(c, c);
+    }
+
     @Override
     public String toString()
     {

src/kademlia/routing/RoutingTable.java

@@ -40,7 +40,7 @@ public class RoutingTable
         this.buckets = new Bucket[NodeId.ID_LENGTH];
         for (int i = 0; i < NodeId.ID_LENGTH; i++)
         {
-            buckets[i] = new KadBucket(i);
+            buckets[i] = new KadBucket(i, this.config);
         }
     }
 
@@ -64,22 +64,6 @@ public class RoutingTable
         this.buckets[this.getBucketId(n.getNodeId())].insert(n);
     }
 
-    /**
-     * Remove a node from the routing table.
-     *
-     * @param n The node to remove
-     */
-    public final void remove(Node n)
-    {
-        int bucketId = this.getBucketId(n.getNodeId());
-
-        /* If the bucket has the contact, remove it */
-        if (this.buckets[bucketId].containsNode(n))
-        {
-            this.buckets[bucketId].removeNode(n);
-        }
-    }
-
     /**
      * Compute the bucket ID in which a given node should be placed; the bucketId is computed based on how far the node is away from the Local Node.
      *
@@ -247,14 +231,27 @@ public class RoutingTable
         {
             return;
         }
-
-        System.out.println("Unresponsive contacts: ");
         for (Node n : contacts)
         {
-            System.out.println(n);
+            this.setUnresponsiveContact(n);
         }
     }
 
+    /**
+     * Method used by operations to notify the routing table of any contacts that have been unresponsive.
+     *
+     * @param n
+     */
+    public synchronized void setUnresponsiveContact(Node n)
+    {
+        int bucketId = this.getBucketId(n.getNodeId());
+
+        //System.out.println(this.localNode + " Removing unresponsive node " + n);
+
+        /* Remove the contact from the bucket */
+        this.buckets[bucketId].removeNode(n);
+    }
+
     @Override
     public synchronized final String toString()
     {

src/kademlia/tests/RoutingTableStateTesting.java

@@ -1,6 +1,7 @@
 package kademlia.tests;
 
 import java.io.IOException;
+import java.util.Scanner;
 import kademlia.KademliaNode;
 import kademlia.dht.KadContent;
 import kademlia.node.NodeId;
@@ -14,33 +15,32 @@ import kademlia.node.NodeId;
 public class RoutingTableStateTesting
 {
 
-    KademliaNode kad0, kad1, kad2, kad3, kad4, kad5, kad6, kad7, kad8, kad9;
+    KademliaNode[] kads;
+
+    public int numKads = 10;
 
     public RoutingTableStateTesting()
     {
         try
         {
-            /* Setting up 2 Kad networks */
+            /* Setting up Kad networks */
-            kad0 = new KademliaNode("user0", new NodeId("HRF456789SD584567460"), 1334);
+            kads = new KademliaNode[numKads];
-            kad1 = new KademliaNode("user1", new NodeId("ASF456789475DS567461"), 1209);
-            kad2 = new KademliaNode("user2", new NodeId("AFG45678947584567462"), 4585);
-            kad3 = new KademliaNode("user3", new NodeId("FSF45J38947584567463"), 8104);
-            kad4 = new KademliaNode("user4", new NodeId("ASF45678947584567464"), 8335);
-            kad5 = new KademliaNode("user5", new NodeId("GHF4567894DR84567465"), 13345);
-            kad6 = new KademliaNode("user6", new NodeId("ASF45678947584567466"), 12049);
-            kad7 = new KademliaNode("user7", new NodeId("AE345678947584567467"), 14585);
-            kad8 = new KademliaNode("user8", new NodeId("ASAA5678947584567468"), 18104);
-            kad9 = new KademliaNode("user9", new NodeId("ASF456789475845674U9"), 18335);
 
-            kad1.bootstrap(kad0.getNode());
+            kads[0] = new KademliaNode("user0", new NodeId("HRF456789SD584567460"), 1334);
-            kad2.bootstrap(kad0.getNode());
+            kads[1] = new KademliaNode("user1", new NodeId("ASF456789475DS567461"), 1209);
-            kad3.bootstrap(kad0.getNode());
+            kads[2] = new KademliaNode("user2", new NodeId("AFG45678947584567462"), 4585);
-            kad4.bootstrap(kad0.getNode());
+            kads[3] = new KademliaNode("user3", new NodeId("FSF45J38947584567463"), 8104);
-            kad5.bootstrap(kad0.getNode());
+            kads[4] = new KademliaNode("user4", new NodeId("ASF45678947584567464"), 8335);
-            kad6.bootstrap(kad0.getNode());
+            kads[5] = new KademliaNode("user5", new NodeId("GHF4567894DR84567465"), 13345);
-            kad7.bootstrap(kad0.getNode());
+            kads[6] = new KademliaNode("user6", new NodeId("ASF45678947584567466"), 12049);
-            kad8.bootstrap(kad0.getNode());
+            kads[7] = new KademliaNode("user7", new NodeId("AE345678947584567467"), 14585);
-            kad9.bootstrap(kad0.getNode());
+            kads[8] = new KademliaNode("user8", new NodeId("ASAA5678947584567468"), 18104);
+            kads[9] = new KademliaNode("user9", new NodeId("ASF456789475845674U9"), 18335);
+
+            for (int i = 1; i < numKads; i++)
+            {
+                kads[i].bootstrap(kads[0].getNode());
+            }
 
             /* Lets shut down a node and then try putting a content on the network. We'll then see how the un-responsive contacts work */
         }
@@ -55,7 +55,7 @@ public class RoutingTableStateTesting
         DHTContentImpl c = null;
         try
         {
-            c = new DHTContentImpl(kad2.getOwnerId(), "Some Data");
+            c = new DHTContentImpl(owner.getOwnerId(), "Some Data");
             owner.put(c);
             return c;
         }
@@ -79,43 +79,71 @@ public class RoutingTableStateTesting
         }
     }
 
+    public void printRoutingTable(int kadId)
+    {
+        System.out.println(kads[kadId].getRoutingTable());
+    }
+
     public void printRoutingTables()
     {
-        System.out.println(kad0.getRoutingTable());
+        for (int i = 0; i < numKads; i++)
-        System.out.println(kad1.getRoutingTable());
+        {
-        System.out.println(kad2.getRoutingTable());
+            this.printRoutingTable(i);
-        System.out.println(kad3.getRoutingTable());
+        }
-        System.out.println(kad4.getRoutingTable());
+    }
-        System.out.println(kad5.getRoutingTable());
+
-        System.out.println(kad6.getRoutingTable());
+    public void printStorage(int kadId)
-        System.out.println(kad7.getRoutingTable());
+    {
-        System.out.println(kad8.getRoutingTable());
+        System.out.println(kads[kadId].getDHT());
-        System.out.println(kad9.getRoutingTable());
     }
 
     public void printStorage()
     {
-        System.out.println(kad0.getDHT());
+        for (int i = 0; i < numKads; i++)
-        System.out.println(kad1.getDHT());
+        {
-        System.out.println(kad2.getDHT());
+            this.printStorage(i);
-        System.out.println(kad3.getDHT());
+        }
-        System.out.println(kad4.getDHT());
-        System.out.println(kad5.getDHT());
-        System.out.println(kad6.getDHT());
-        System.out.println(kad7.getDHT());
-        System.out.println(kad8.getDHT());
-        System.out.println(kad9.getDHT());
     }
 
     public static void main(String[] args)
     {
+
         RoutingTableStateTesting rtss = new RoutingTableStateTesting();
-        rtss.printRoutingTables();
 
-        /* Lets shut down a node to test the node removal operation */
+        try
-        rtss.shutdownKad(rtss.kad3);
+        {
+            rtss.printRoutingTables();
 
-        rtss.putContent("Content owned by kad0", rtss.kad0);
+            /* Lets shut down a node to test the node removal operation */
-        rtss.printStorage();
+            rtss.shutdownKad(rtss.kads[3]);
+
+            rtss.putContent("Content owned by kad0", rtss.kads[0]);
+            rtss.printStorage();
+
+            Thread.sleep(1000);
+
+            /* kad3 should be removed from their routing tables by now. */
+            rtss.printRoutingTables();
+        }
+        catch (InterruptedException ex)
+        {
+
+        }
+
+        Scanner sc = new Scanner(System.in);
+        while (true)
+        {
+            System.out.println("\n\n ************************* Options **************************** \n");
+            System.out.println("1 i - Print routing table of node i");
+            int val1 = sc.nextInt();
+            int val2 = sc.nextInt();
+
+            switch (val1)
+            {
+                case 1:
+                    rtss.printRoutingTable(val2);
+                    break;
+            }
+        }
     }
 }