package socialkademlia.operation;
import kademlia.message.Receiver;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
import kademlia.KadConfiguration;
import kademlia.KadServer;
import kademlia.exceptions.RoutingException;
import kademlia.message.Message;
import kademlia.message.NodeLookupMessage;
import kademlia.message.NodeReplyMessage;
import kademlia.node.KeyComparator;
import kademlia.node.Node;
import kademlia.node.KademliaId;
import kademlia.operation.Operation;
import socialkademlia.SocialKademliaNode;
/**
* Finds the K closest nodes to a specified identifier
* The algorithm terminates when it has gotten responses from the K closest nodes it has seen.
* Nodes that fail to respond are removed from consideration
*
* @author Joshua Kissoon
* @created 20140219
*/
public class NodeLookupOperation implements Operation, Receiver
{
/* Constants */
private static final String UNASKED = "UnAsked";
private static final String AWAITING = "Awaiting";
private static final String ASKED = "Asked";
private static final String FAILED = "Failed";
private final KadServer server;
private final SocialKademliaNode localNode;
private final KadConfiguration config;
private final Message lookupMessage; // Message sent to each peer
private final Map<Node, String> nodes;
/* Tracks messages in transit and awaiting reply */
private final Map<Integer, Node> messagesTransiting;
/* Used to sort nodes */
private final Comparator comparator;
{
messagesTransiting = new HashMap<>();
}
/**
* @param server KadServer used for communication
* @param localNode The local node making the communication
* @param lookupId The ID for which to find nodes close to
* @param config
*/
public NodeLookupOperation(KadServer server, SocialKademliaNode localNode, KademliaId lookupId, KadConfiguration config)
{
this.server = server;
this.localNode = localNode;
this.config = config;
this.lookupMessage = new NodeLookupMessage(localNode.getNode(), lookupId);
/**
* We initialize a TreeMap to store nodes.
* This map will be sorted by which nodes are closest to the lookupId
*/
this.comparator = new KeyComparator(lookupId);
this.nodes = new TreeMap(this.comparator);
}
/**
* @throws java.io.IOException
* @throws kademlia.exceptions.RoutingException
*/
@Override
public synchronized void execute() throws IOException, RoutingException
{
try
{
/* Set the local node as already asked */
nodes.put(this.localNode.getNode(), ASKED);
/**
* We add all nodes here instead of the K-Closest because there may be the case that the K-Closest are offline
* - The operation takes care of looking at the K-Closest.
*/
this.addNodes(this.localNode.getRoutingTable().getAllNodes());
/* If we haven't finished as yet, wait for a maximum of config.operationTimeout() time */
int totalTimeWaited = 0;
int timeInterval = 10; // We re-check every n milliseconds
while (totalTimeWaited < this.config.operationTimeout())
{
if (!this.askNodesorFinish())
{
wait(timeInterval);
totalTimeWaited += timeInterval;
}
else
{
break;
}
}
/* Now after we've finished, we would have an idea of offline nodes, lets update our routing table */
this.localNode.getRoutingTable().setUnresponsiveContacts(this.getFailedNodes());
}
catch (InterruptedException e)
{
throw new RuntimeException(e);
}
}
public List<Node> getClosestNodes()
{
return this.closestNodes(ASKED);
}
/**
* Add nodes from this list to the set of nodes to lookup
*
* @param list The list from which to add nodes
*/
public void addNodes(List<Node> list)
{
for (Node o : list)
{
/* If this node is not in the list, add the node */
if (!nodes.containsKey(o))
{
nodes.put(o, UNASKED);
}
}
}
/**
* Asks some of the K closest nodes seen but not yet queried.
* Assures that no more than DefaultConfiguration.CONCURRENCY messages are in transit at a time
*
* This method should be called every time a reply is received or a timeout occurs.
*
* If all K closest nodes have been asked and there are no messages in transit,
* the algorithm is finished.
*
* @return <code>true</code> if finished OR <code>false</code> otherwise
*/
private boolean askNodesorFinish() throws IOException
{
/* If >= CONCURRENCY nodes are in transit, don't do anything */
if (this.config.maxConcurrentMessagesTransiting() <= this.messagesTransiting.size())
{
return false;
}
/* Get unqueried nodes among the K closest seen that have not FAILED */
List<Node> unasked = this.closestNodesNotFailed(UNASKED);
if (unasked.isEmpty() && this.messagesTransiting.isEmpty())
{
/* We have no unasked nodes nor any messages in transit, we're finished! */
return true;
}
/**
* Send messages to nodes in the list;
* making sure than no more than CONCURRENCY messsages are in transit
*/
for (int i = 0; (this.messagesTransiting.size() < this.config.maxConcurrentMessagesTransiting()) && (i < unasked.size()); i++)
{
Node n = (Node) unasked.get(i);
int comm = server.sendMessage(n, lookupMessage, this);
this.nodes.put(n, AWAITING);
this.messagesTransiting.put(comm, n);
}
/* We're not finished as yet, return false */
return false;
}
/**
* @param status The status of the nodes to return
*
* @return The K closest nodes to the target lookupId given that have the specified status
*/
private List<Node> closestNodes(String status)
{
List<Node> closestNodes = new ArrayList<>(this.config.k());
int remainingSpaces = this.config.k();
for (Map.Entry e : this.nodes.entrySet())
{
if (status.equals(e.getValue()))
{
/* We got one with the required status, now add it */
closestNodes.add((Node) e.getKey());
if (--remainingSpaces == 0)
{
break;
}
}
}
return closestNodes;
}
/**
* Find The K closest nodes to the target lookupId given that have not FAILED.
* From those K, get those that have the specified status
*
* @param status The status of the nodes to return
*
* @return A List of the closest nodes
*/
private List<Node> closestNodesNotFailed(String status)
{
List<Node> closestNodes = new ArrayList<>(this.config.k());
int remainingSpaces = this.config.k();
for (Map.Entry<Node, String> e : this.nodes.entrySet())
{
if (!FAILED.equals(e.getValue()))
{
if (status.equals(e.getValue()))
{
/* We got one with the required status, now add it */
closestNodes.add(e.getKey());
}
if (--remainingSpaces == 0)
{
break;
}
}
}
return closestNodes;
}
/**
* Receive and handle the incoming NodeReplyMessage
*
* @param comm
*
* @throws java.io.IOException
*/
@Override
public synchronized void receive(Message incoming, int comm) throws IOException
{
if (!(incoming instanceof NodeReplyMessage))
{
/* Not sure why we get a message of a different type here... @todo Figure it out. */
return;
}
/* We receive a NodeReplyMessage with a set of nodes, read this message */
NodeReplyMessage msg = (NodeReplyMessage) incoming;
/* Add the origin node to our routing table */
Node origin = msg.getOrigin();
this.localNode.getRoutingTable().insert(origin);
/* Set that we've completed ASKing the origin node */
this.nodes.put(origin, ASKED);
/* Remove this msg from messagesTransiting since it's completed now */
this.messagesTransiting.remove(comm);
/* Add the received nodes to our nodes list to query */
this.addNodes(msg.getNodes());
this.askNodesorFinish();
}
/**
* A node does not respond or a packet was lost, we set this node as failed
*
* @param comm
*
* @throws java.io.IOException
*/
@Override
public synchronized void timeout(int comm) throws IOException
{
/* Get the node associated with this communication */
Node n = this.messagesTransiting.get(comm);
if (n == null)
{
return;
}
/* Mark this node as failed and inform the routing table that it is unresponsive */
this.nodes.put(n, FAILED);
this.localNode.getRoutingTable().setUnresponsiveContact(n);
this.messagesTransiting.remove(comm);
this.askNodesorFinish();
}
public List<Node> getFailedNodes()
{
List<Node> failedNodes = new ArrayList<>();
for (Map.Entry<Node, String> e : this.nodes.entrySet())
{
if (e.getValue().equals(FAILED))
{
failedNodes.add(e.getKey());
}
}
return failedNodes;
}
}