X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/9932a0c0d2c44e34633c97a827b2b04d615cb4e9..903d96f4c7e2f761608b4591faa573aab5891994:/examples/java/chord/Node.java

diff --git a/examples/java/chord/Node.java b/examples/java/chord/Node.java
index 93099237ae..6456b6b3c4 100644
--- a/examples/java/chord/Node.java
+++ b/examples/java/chord/Node.java
@@ -6,473 +6,410 @@
 
 package chord;
 
+import org.simgrid.msg.Msg;
 import org.simgrid.msg.Comm;
 import org.simgrid.msg.Host;
-import org.simgrid.msg.Msg;
-import org.simgrid.msg.MsgException;
-import org.simgrid.msg.Process;
 import org.simgrid.msg.Task;
+import org.simgrid.msg.Process;
+import org.simgrid.msg.MsgException;
 import org.simgrid.msg.TimeoutException;
-/**
- * Node data
- */
 public class Node extends Process {
-	/**
-	 * Node id
-	 */
-	protected int id;
-	/**
-	 * Node mailbox
-	 */
-	protected String mailbox;
-	/**
-	 * Predecessor id
-	 */
-	protected int predId;
-	/**
-	 * Predecessor mailbox
-	 */
-	protected String predMailbox;
-	/**
-	 * Index of the next finger to fix
-	 */
-	protected int nextFingerToFix;
-	/**
-	 * Current communication
-	 */
-	protected Comm commReceive;
-	/**
-	 * Last time I changed a finger or my predecessor
-	 */
-	protected double lastChangeDate;
-	/**
-	 * Node fingers
-	 */
-	int fingers[];
-	/**
-	 * Constructor
-	 */
-	public Node(Host host, String name, String[] args) {
-		super(host,name,args);
-	}
-	@Override
-	public void main(String[] args) throws MsgException {
-		if (args.length != 2 && args.length != 4) {
-			Msg.info("You need to provide 2 or 4 arguments.");
-			return;	
-		}
-		double initTime = Msg.getClock();
-		int i;
-		boolean joinSuccess = false;
-		double deadline;
-		
-		double nextStabilizeDate = initTime + Common.PERIODIC_STABILIZE_DELAY;
-		double nextFixFingersDate = initTime + Common.PERIODIC_FIX_FINGERS_DELAY;
-		double nextCheckPredecessorDate = initTime + Common.PERIODIC_CHECK_PREDECESSOR_DELAY;
-		double nextLookupDate = initTime + Common.PERIODIC_LOOKUP_DELAY;
-		
-		id = Integer.valueOf(args[0]);
-		mailbox = Integer.toString(id);
-
-		fingers = new int[Common.NB_BITS];
-		for (i = 0; i < Common.NB_BITS; i++) {
-			fingers[i] = -1;
-			setFinger(i,this.id);
-		}
-		
-		//First node
-		if (args.length == 2) {
-			deadline = Integer.valueOf(args[1]);
-			create();
-			joinSuccess = true;
-		}
-		else {
-			int knownId = Integer.valueOf(args[1]);
-			deadline = Integer.valueOf(args[3]);
-			//Msg.info("Hey! Let's join the system with the id " + id + ".");
-			
-			joinSuccess = join(knownId);
-		}
-		if (joinSuccess) {
-			double currentClock = Msg.getClock();
-			while (currentClock < (initTime + deadline) && currentClock < Common.MAX_SIMULATION_TIME) {
-				if (commReceive == null) {
-					commReceive = Task.irecv(this.mailbox);
-				}
-				try {
-					if (!commReceive.test()) {
-						if (currentClock >= nextStabilizeDate) {
-							stabilize();
-							nextStabilizeDate = Msg.getClock() + Common.PERIODIC_STABILIZE_DELAY;
-						}
-						else if (currentClock >= nextFixFingersDate) {
-							fixFingers();
-							nextFixFingersDate = Msg.getClock() + Common.PERIODIC_FIX_FINGERS_DELAY;
-						}
-						else if (currentClock >= nextCheckPredecessorDate) {
-							this.checkPredecessor();
-							nextCheckPredecessorDate = Msg.getClock() + Common.PERIODIC_CHECK_PREDECESSOR_DELAY;
-						}
-						else if (currentClock >= nextLookupDate) {
-							this.randomLookup();
-							nextLookupDate = Msg.getClock() + Common.PERIODIC_LOOKUP_DELAY;
-						}
-						else {
-							waitFor(5);
-						}
-						currentClock = Msg.getClock();
-					}
-					else {
-						handleTask(commReceive.getTask());
-						currentClock = Msg.getClock();
-						commReceive = null;
-						
-					}
-				}
-				catch (Exception e) {
-					currentClock = Msg.getClock();
-					commReceive = null;
-				}
-				
-			}
-			leave();
-			if (commReceive != null) {
-				commReceive = null;
-			}
-		}
-		else {
-			Msg.info("I couldn't join the ring");
-		}
-	}
-	void handleTask(Task task) {
-		if (task instanceof FindSuccessorTask) {
-			FindSuccessorTask fTask = (FindSuccessorTask)task;
-			Msg.debug("Receiving a 'Find Successor' request from " + fTask.issuerHostName + " for id " + fTask.requestId);
-			// is my successor the successor?
-			if (isInInterval(fTask.requestId, this.id + 1, fingers[0])) {
-				//Msg.info("Send the request to " + fTask.answerTo + " with answer " + fingers[0]);
-				FindSuccessorAnswerTask answer = new FindSuccessorAnswerTask(getHost().getName(), mailbox, fingers[0]);
-				answer.dsend(fTask.answerTo);
-			}
-			else {
-		        // otherwise, forward the request to the closest preceding finger in my table
-				int closest = closestPrecedingNode(fTask.requestId);
-				//Msg.info("Forward the request to " + closest);
-				fTask.dsend(Integer.toString(closest));
-			}
-		}
-		else if (task instanceof GetPredecessorTask) {
-			GetPredecessorTask gTask = (GetPredecessorTask)(task);
-			Msg.debug("Receiving a 'Get Predecessor' request from " + gTask.issuerHostName);
-			GetPredecessorAnswerTask answer = new GetPredecessorAnswerTask(getHost().getName(), mailbox, predId);
-			answer.dsend(gTask.answerTo);
-		}
-		else if (task instanceof NotifyTask) {
-			NotifyTask nTask = (NotifyTask)task;
-			notify(nTask.requestId);
-		}
-		else {
-			Msg.debug("Ignoring unexpected task of type:" + task);
-		}
-	}
-	/**
-	 * @brief Makes the current node quit the system
-	 */
-	void leave() {
-		Msg.debug("Well Guys! I Think it's time for me to quit ;)");
-		quitNotify(1); //Notify my successor
-		quitNotify(-1); //Notify my predecessor.
-		// TODO ...
-	}
-	/**
-	 * @brief Notifies the successor or the predecessor of the current node
-	 * of the departure
-	 * @param to 1 to notify the successor, -1 to notify the predecessor
-	 */
-	static void quitNotify( int to) {
-		//TODO
-	}
-	/**
-      * @brief Initializes the current node as the first one of the system.
-	 */
-	void create() {
-		Msg.debug("Create a new Chord ring...");
-		setPredecessor(-1);
-		
-	}
-	/**
-	 * Makes the current node join the ring, knowing the id of a node
-	 * already in the ring 
-	 */
-	boolean join(int knownId) {
-		Msg.info("Joining the ring with id " + this.id + " knowing node " + knownId);
-		setPredecessor(-1);
-		int successorId = remoteFindSuccessor(knownId, this.id);
-		if (successorId == -1) {
-			Msg.info("Cannot join the ring.");
-		}
-		else {
-			setFinger(0, successorId);
-		}
-		return successorId != -1;
-	}
-	
-	/**
-	 * Sets the node predecessor
-	 */
-	void setPredecessor(int predecessorId) {
-		if (predecessorId != predId) {
-			predId = predecessorId;
-			if (predecessorId != -1) {
-				predMailbox = Integer.toString(predId);
-			}
-			lastChangeDate = Msg.getClock();
-		}
-	}
-	/**
-	 * @brief Asks another node its predecessor.
-	 * @param askTo the node to ask to
-	 * @return the id of its predecessor node, or -1 if the request failed
-	 * (or if the node does not know its predecessor)
-	 */
-	int remoteGetPredecessor(int askTo) {
-		int predecessorId = -1;
-		boolean stop = false;
-		Msg.debug("Sending a 'Get Predecessor' request to " + askTo);
-		String mailboxTo = Integer.toString(askTo);
-		GetPredecessorTask sendTask = new GetPredecessorTask(getHost().getName(), this.mailbox);
-		try {
-			sendTask.send(mailboxTo, Common.TIMEOUT);			
-			try {
-				do {
-					if (commReceive == null) {
-						commReceive = Task.irecv(this.mailbox);
-					}
-					commReceive.waitCompletion(Common.TIMEOUT);
-					Task taskReceived = commReceive.getTask();
-					if (taskReceived instanceof GetPredecessorAnswerTask) {
-						predecessorId = ((GetPredecessorAnswerTask) taskReceived).answerId;
-						stop = true;
-					}
-					else {
-						handleTask(taskReceived);
-					}
-					commReceive = null;					
-				} while (!stop);
-		
-			}
-			catch (MsgException e) {
-				commReceive = null;	
-				stop = true;
-			}
-		}
-		catch (MsgException e) {
-			Msg.debug("Failed to send the Get Predecessor request");
-		}
-		
-		
-		return predecessorId;
-	}
-	/**
-	 * @brief Makes the current node find the successor node of an id.
-	 * @param node the current node
-	 * @param id the id to find
-	 * @return the id of the successor node, or -1 if the request failed
-	 */
-	int findSuccessor(int id) {
-		if (isInInterval(id, this.id + 1, fingers[0])) {
-			return fingers[0];
-		}
-		
-		int closest = this.closestPrecedingNode(id);
-		return remoteFindSuccessor(closest, id);
-	}
-	/**
-	 * @brief Asks another node the successor node of an id.
-	 */
-	int remoteFindSuccessor(int askTo, int id) {
-		int successor = -1;
-		boolean stop = false;
-		String mailbox = Integer.toString(askTo);
-		Task sendTask = new FindSuccessorTask(getHost().getName(), this.mailbox, id);
-		Msg.debug("Sending a 'Find Successor' request to " + mailbox + " for id " + id);
-		try {
-			sendTask.send(mailbox, Common.TIMEOUT);
-			do {
-				if (commReceive == null) {
-					commReceive = Task.irecv(this.mailbox);
-				}
-				try {
-					commReceive.waitCompletion(Common.TIMEOUT);
-					Task task = commReceive.getTask();
-					if (task instanceof FindSuccessorAnswerTask) {
-						//TODO: Check if this this our answer.
-						FindSuccessorAnswerTask fTask = (FindSuccessorAnswerTask) task;
-						stop = true;
-						successor = fTask.answerId;
-					}
-					else {
-						handleTask(task);
-					}
-					commReceive = null;
-				}
-				catch (TimeoutException e) {
-					stop = true;
-					commReceive = null;
-				}
-			} while (!stop);
-		}
-		catch (TimeoutException e) {
-			Msg.debug("Failed to send the 'Find Successor' request");
-		}
-		catch (MsgException e) {
-			Msg.debug("Failed to receive Find Successor");
-		}
-		
-		return successor;
-
-	}
-	/**
-	 * @brief This function is called periodically. It checks the immediate
-	 * successor of the current node.
-	 */
-	void stabilize() {
-		Msg.debug("Stabilizing node");
-		int candidateId;
-		int successorId = fingers[0];
-		if (successorId != this.id){
-			candidateId = remoteGetPredecessor(successorId);
-		}
-		else {
-			candidateId = predId;
-		}
-		//This node is a candidate to become my new successor
-		if (candidateId != -1 && isInInterval(candidateId, this.id + 1, successorId - 1)) {
-			setFinger(0, candidateId);
-		}
-		if (successorId != this.id) {
-			remoteNotify(successorId, this.id);
-		}
-		
-	}
-	/**
-	 * \brief Notifies the current node that its predecessor may have changed.
-	 * \param candidate_id the possible new predecessor
-	 */
-	void notify(int predecessorCandidateId) {
-		if (predId == -1 || isInInterval(predecessorCandidateId, predId + 1, this.id - 1 )) {
-			setPredecessor(predecessorCandidateId);
-		}
-		else {
-			//Don't have to change the predecessor.
-		}
-	}
-	/**
-	 * \brief Notifies a remote node that its predecessor may have changed.
-	 * \param notify_id id of the node to notify
-	 * \param candidate_id the possible new predecessor
-	 */	
-	void remoteNotify(int notifyId, int predecessorCandidateId) {
-		Msg.debug("Sending a 'Notify' request to " + notifyId);
-		Task sentTask = new NotifyTask(getHost().getName(), this.mailbox, predecessorCandidateId);
-		sentTask.dsend(Integer.toString(notifyId));
-	}
-	/**
-	 * \brief This function is called periodically.
-	 * It refreshes the finger table of the current node.
-	 */
-	void fixFingers() {
-		Msg.debug("Fixing fingers");
-		int i = this.nextFingerToFix;
-		int id = this.findSuccessor(this.id + (int)Math.pow(2,i)); //FIXME: SLOW
-		if (id != -1) {
-			if (id != fingers[i]) {
-				setFinger(i, id);
-			}
-			nextFingerToFix = (i + 1) % Common.NB_BITS;
-		}
-	}
-	/**
-	 * \brief This function is called periodically.
-	 * It checks whether the predecessor has failed
-	 */
-	void checkPredecessor() {
-		//TODO
-	}
-	/**
-	 * \brief Performs a find successor request to a random id.
-	 */
-	void randomLookup() {
-		int id = 1337;
-		//Msg.info("Making a lookup request for id " + id);
-		findSuccessor(id);
-	}
-	
-	
-
-	/**
-	 * @brief Returns the closest preceding finger of an id
-	 * with respect to the finger table of the current node.
-	 * @param id the id to find
-	 * \return the closest preceding finger of that id
-	 */
-	int closestPrecedingNode(int id) {
-		int i;
-		for (i = Common.NB_BITS - 1; i >= 0; i--) {
-			if (isInInterval(fingers[i], this.id + 1, id - 1)) {
-				return fingers[i];
-			}
-		}		
-		return this.id;
-	}
-	/**
-	 * @brief Returns whether an id belongs to the interval [start, end].
-	 *
-	 * The parameters are noramlized to make sure they are between 0 and nb_keys - 1).
-	 * 1 belongs to [62, 3]
-	 * 1 does not belong to [3, 62]
-	 * 63 belongs to [62, 3]
-	 * 63 does not belong to [3, 62]
-	 * 24 belongs to [21, 29]
-	 * 24 does not belong to [29, 21]
-	 *
-	 * \param id id to check
-	 * \param start lower bound
-	 * \param end upper bound
-	 * \return a non-zero value if id in in [start, end]
-	 */
-	static boolean isInInterval(int id, int start, int end) {
-		id = normalize(id);
-		start = normalize(start);
-		end = normalize(end);
-		
-		// make sure end >= start and id >= start
-		if (end < start) {
-			end += Common.NB_KEYS;
-		}
-		if (id < start) {
-			id += Common.NB_KEYS;
-		}
-		return (id <= end);
-	
-	}
-	/**
-	 * @brief Turns an id into an equivalent id in [0, nb_keys).
-	 * @param id an id
-	 * @return the corresponding normalized id
-	 */
-	static int normalize(int id) {
-		return id & (Common.NB_KEYS - 1);
-	}
-	/**
-	 * \brief Sets a finger of the current node.
-	 * \param finger_index index of the finger to set (0 to nb_bits - 1)
-	 * \param id the id to set for this finger
-	 */
-	void setFinger(int fingerIndex, int id) {
-		if (id != fingers[fingerIndex]) {
-			fingers[fingerIndex] = id;
-			lastChangeDate = Msg.getClock();
-		}
-	}
+  protected int id;
+  protected String mailbox;
+  protected int predId;
+  protected String predMailbox;
+  protected int nextFingerToFix;
+  protected Comm commReceive;
+  ///Last time I changed a finger or my predecessor
+  protected double lastChangeDate;
+  int fingers[];
+
+  public Node(Host host, String name, String[] args) {
+    super(host,name,args);
+  }
+
+  @Override
+  public void main(String[] args) throws MsgException {
+    if (args.length != 2 && args.length != 4) {
+      Msg.info("You need to provide 2 or 4 arguments.");
+      return;
+    }
+    double initTime = Msg.getClock();
+    int i;
+    boolean joinSuccess = false;
+    double deadline;
+
+    double nextStabilizeDate = initTime + Common.PERIODIC_STABILIZE_DELAY;
+    double nextFixFingersDate = initTime + Common.PERIODIC_FIX_FINGERS_DELAY;
+    double nextCheckPredecessorDate = initTime + Common.PERIODIC_CHECK_PREDECESSOR_DELAY;
+    double nextLookupDate = initTime + Common.PERIODIC_LOOKUP_DELAY;
+
+    id = Integer.valueOf(args[0]);
+    mailbox = Integer.toString(id);
+
+    fingers = new int[Common.NB_BITS];
+    for (i = 0; i < Common.NB_BITS; i++) {
+      fingers[i] = -1;
+      setFinger(i,this.id);
+    }
+
+    //First node
+    if (args.length == 2) {
+      deadline = Integer.valueOf(args[1]);
+      create();
+      joinSuccess = true;
+    } else {
+      int knownId = Integer.valueOf(args[1]);
+      deadline = Integer.valueOf(args[3]);
+      //Msg.info("Hey! Let's join the system with the id " + id + ".");
+
+      joinSuccess = join(knownId);
+    }
+    if (joinSuccess) {
+      double currentClock = Msg.getClock();
+      while (currentClock < (initTime + deadline) && currentClock < Common.MAX_SIMULATION_TIME) {
+        if (commReceive == null) {
+          commReceive = Task.irecv(this.mailbox);
+        }
+        try {
+          if (!commReceive.test()) {
+            if (currentClock >= nextStabilizeDate) {
+              stabilize();
+              nextStabilizeDate = Msg.getClock() + Common.PERIODIC_STABILIZE_DELAY;
+            } else if (currentClock >= nextFixFingersDate) {
+              fixFingers();
+              nextFixFingersDate = Msg.getClock() + Common.PERIODIC_FIX_FINGERS_DELAY;
+            } else if (currentClock >= nextCheckPredecessorDate) {
+              this.checkPredecessor();
+              nextCheckPredecessorDate = Msg.getClock() + Common.PERIODIC_CHECK_PREDECESSOR_DELAY;
+            } else if (currentClock >= nextLookupDate) {
+              this.randomLookup();
+              nextLookupDate = Msg.getClock() + Common.PERIODIC_LOOKUP_DELAY;
+            } else {
+              waitFor(5);
+            }
+            currentClock = Msg.getClock();
+          } else {
+            handleTask(commReceive.getTask());
+            currentClock = Msg.getClock();
+            commReceive = null;
+          }
+        }
+        catch (Exception e) {
+          currentClock = Msg.getClock();
+          commReceive = null;
+        }
+      }
+      leave();
+      if (commReceive != null) {
+        commReceive = null;
+      }
+    } else {
+      Msg.info("I couldn't join the ring");
+    }
+  }
+
+  void handleTask(Task task) {
+    if (task instanceof FindSuccessorTask) {
+      FindSuccessorTask fTask = (FindSuccessorTask)task;
+      Msg.debug("Receiving a 'Find Successor' request from " + fTask.issuerHostName + " for id " + fTask.requestId);
+      // is my successor the successor?
+      if (isInInterval(fTask.requestId, this.id + 1, fingers[0])) {
+        //Msg.info("Send the request to " + fTask.answerTo + " with answer " + fingers[0]);
+        FindSuccessorAnswerTask answer = new FindSuccessorAnswerTask(getHost().getName(), mailbox, fingers[0]);
+        answer.dsend(fTask.answerTo);
+      } else {
+        // otherwise, forward the request to the closest preceding finger in my table
+        int closest = closestPrecedingNode(fTask.requestId);
+        //Msg.info("Forward the request to " + closest);
+        fTask.dsend(Integer.toString(closest));
+      }
+    } else if (task instanceof GetPredecessorTask) {
+      GetPredecessorTask gTask = (GetPredecessorTask)(task);
+      Msg.debug("Receiving a 'Get Predecessor' request from " + gTask.issuerHostName);
+      GetPredecessorAnswerTask answer = new GetPredecessorAnswerTask(getHost().getName(), mailbox, predId);
+      answer.dsend(gTask.answerTo);
+    } else if (task instanceof NotifyTask) {
+      NotifyTask nTask = (NotifyTask)task;
+      notify(nTask.requestId);
+    } else {
+      Msg.debug("Ignoring unexpected task of type:" + task);
+    }
+  }
+
+  void leave() {
+    Msg.debug("Well Guys! I Think it's time for me to quit ;)");
+    quitNotify(1); //Notify my successor
+    quitNotify(-1); //Notify my predecessor.
+  }
+
+  /**
+   * @brief Notifies the successor or the predecessor of the current node of the departure
+   * @param to 1 to notify the successor, -1 to notify the predecessor
+   */
+  static void quitNotify( int to) {
+    //TODO
+  }
+
+  /**
+   * @brief Initializes the current node as the first one of the system.
+   */
+  void create() {
+    Msg.debug("Create a new Chord ring...");
+    setPredecessor(-1);
+  }
+
+  // Makes the current node join the ring, knowing the id of a node already in the ring 
+  boolean join(int knownId) {
+    Msg.info("Joining the ring with id " + this.id + " knowing node " + knownId);
+    setPredecessor(-1);
+    int successorId = remoteFindSuccessor(knownId, this.id);
+    if (successorId == -1) {
+      Msg.info("Cannot join the ring.");
+    } else {
+      setFinger(0, successorId);
+    }
+    return successorId != -1;
+  }
+
+  void setPredecessor(int predecessorId) {
+    if (predecessorId != predId) {
+      predId = predecessorId;
+      if (predecessorId != -1) {
+        predMailbox = Integer.toString(predId);
+      }
+      lastChangeDate = Msg.getClock();
+    }
+  }
+
+  /**
+   * @brief Asks another node its predecessor.
+   * @param askTo the node to ask to
+   * @return the id of its predecessor node, or -1 if the request failed(or if the node does not know its predecessor)
+   */
+  int remoteGetPredecessor(int askTo) {
+    int predecessorId = -1;
+    boolean stop = false;
+    Msg.debug("Sending a 'Get Predecessor' request to " + askTo);
+    String mailboxTo = Integer.toString(askTo);
+    GetPredecessorTask sendTask = new GetPredecessorTask(getHost().getName(), this.mailbox);
+    try {
+      sendTask.send(mailboxTo, Common.TIMEOUT);
+      try {
+        do {
+          if (commReceive == null) {
+            commReceive = Task.irecv(this.mailbox);
+          }
+          commReceive.waitCompletion(Common.TIMEOUT);
+          Task taskReceived = commReceive.getTask();
+          if (taskReceived instanceof GetPredecessorAnswerTask) {
+            predecessorId = ((GetPredecessorAnswerTask) taskReceived).answerId;
+            stop = true;
+          } else {
+            handleTask(taskReceived);
+          }
+          commReceive = null;
+        } while (!stop);
+      }
+      catch (MsgException e) {
+        commReceive = null;
+        stop = true;
+      }
+    }
+    catch (MsgException e) {
+      Msg.debug("Failed to send the Get Predecessor request");
+    }
+    return predecessorId;
+  }
+
+  /**
+   * @brief Makes the current node find the successor node of an id.
+   * @param node the current node
+   * @param id the id to find
+   * @return the id of the successor node, or -1 if the request failed
+   */
+  int findSuccessor(int id) {
+    if (isInInterval(id, this.id + 1, fingers[0])) {
+      return fingers[0];
+    }
+
+    int closest = this.closestPrecedingNode(id);
+    return remoteFindSuccessor(closest, id);
+  }
+
+  // Asks another node the successor node of an id.
+  int remoteFindSuccessor(int askTo, int id) {
+    int successor = -1;
+    boolean stop = false;
+    String mailbox = Integer.toString(askTo);
+    Task sendTask = new FindSuccessorTask(getHost().getName(), this.mailbox, id);
+    Msg.debug("Sending a 'Find Successor' request to " + mailbox + " for id " + id);
+    try {
+      sendTask.send(mailbox, Common.TIMEOUT);
+      do {
+        if (commReceive == null) {
+          commReceive = Task.irecv(this.mailbox);
+        }
+        try {
+          commReceive.waitCompletion(Common.TIMEOUT);
+          Task task = commReceive.getTask();
+          if (task instanceof FindSuccessorAnswerTask) {
+            //TODO: Check if this this our answer.
+            FindSuccessorAnswerTask fTask = (FindSuccessorAnswerTask) task;
+            stop = true;
+            successor = fTask.answerId;
+          } else {
+            handleTask(task);
+          }
+          commReceive = null;
+        }
+        catch (TimeoutException e) {
+          stop = true;
+          commReceive = null;
+        }
+      } while (!stop);
+    }
+    catch (TimeoutException e) {
+      Msg.debug("Failed to send the 'Find Successor' request");
+    }
+    catch (MsgException e) {
+      Msg.debug("Failed to receive Find Successor");
+    }
+
+    return successor;
+  }
+
+  // This function is called periodically. It checks the immediate successor of the current node.
+  void stabilize() {
+    Msg.debug("Stabilizing node");
+    int candidateId;
+    int successorId = fingers[0];
+    if (successorId != this.id){
+      candidateId = remoteGetPredecessor(successorId);
+    } else {
+      candidateId = predId;
+    }
+    //This node is a candidate to become my new successor
+    if (candidateId != -1 && isInInterval(candidateId, this.id + 1, successorId - 1)) {
+      setFinger(0, candidateId);
+    }
+    if (successorId != this.id) {
+      remoteNotify(successorId, this.id);
+    }
+  }
+
+  /**
+   * @brief Notifies the current node that its predecessor may have changed.
+   * @param candidate_id the possible new predecessor
+   */
+  void notify(int predecessorCandidateId) {
+    if (predId == -1 || isInInterval(predecessorCandidateId, predId + 1, this.id - 1 )) {
+      setPredecessor(predecessorCandidateId);
+    }
+  }
+
+  /**
+   * @brief Notifies a remote node that its predecessor may have changed.
+   * @param notify_id id of the node to notify
+   * @param candidate_id the possible new predecessor
+   */
+  void remoteNotify(int notifyId, int predecessorCandidateId) {
+    Msg.debug("Sending a 'Notify' request to " + notifyId);
+    Task sentTask = new NotifyTask(getHost().getName(), this.mailbox, predecessorCandidateId);
+    sentTask.dsend(Integer.toString(notifyId));
+  }
+
+  // This function is called periodically.
+  // It refreshes the finger table of the current node.
+  void fixFingers() {
+    Msg.debug("Fixing fingers");
+    int i = this.nextFingerToFix;
+    int id = this.findSuccessor(this.id + (int)Math.pow(2,i)); //FIXME: SLOW
+    if (id != -1) {
+      if (id != fingers[i]) {
+        setFinger(i, id);
+      }
+      nextFingerToFix = (i + 1) % Common.NB_BITS;
+    }
+  }
+
+  // This function is called periodically.
+  // It checks whether the predecessor has failed
+  void checkPredecessor() {
+    //TODO
+  }
+
+  // Performs a find successor request to a random id.
+  void randomLookup() {
+    int id = 1337;
+    //Msg.info("Making a lookup request for id " + id);
+    findSuccessor(id);
+  }
+
+  /**
+   * @brief Returns the closest preceding finger of an id with respect to the finger table of the current node.
+   * @param id the id to find
+   * @return the closest preceding finger of that id
+   */
+  int closestPrecedingNode(int id) {
+    int i;
+    for (i = Common.NB_BITS - 1; i >= 0; i--) {
+      if (isInInterval(fingers[i], this.id + 1, id - 1)) {
+        return fingers[i];
+      }
+    }
+    return this.id;
+  }
+
+  /**
+   * @brief Returns whether an id belongs to the interval [start, end].
+   *
+   * The parameters are noramlized to make sure they are between 0 and nb_keys - 1).
+   * 1 belongs to [62, 3]
+   * 1 does not belong to [3, 62]
+   * 63 belongs to [62, 3]
+   * 63 does not belong to [3, 62]
+   * 24 belongs to [21, 29]
+   * 24 does not belong to [29, 21]
+   *
+   * @param id id to check
+   * @param start lower bound
+   * @param end upper bound
+   * @return a non-zero value if id in in [start, end]
+   */
+  static boolean isInInterval(int id, int start, int end) {
+    id = normalize(id);
+    start = normalize(start);
+    end = normalize(end);
+
+    // make sure end >= start and id >= start
+    if (end < start) {
+      end += Common.NB_KEYS;
+    }
+    if (id < start) {
+      id += Common.NB_KEYS;
+    }
+    return (id <= end);
+  }
+
+  /**
+   * @brief Turns an id into an equivalent id in [0, nb_keys).
+   * @param id an id
+   * @return the corresponding normalized id
+   */
+  static int normalize(int id) {
+    return id & (Common.NB_KEYS - 1);
+  }
+
+  /**
+   * @brief Sets a finger of the current node.
+   * @param finger_index index of the finger to set (0 to nb_bits - 1)
+   * @param id the id to set for this finger
+   */
+  void setFinger(int fingerIndex, int id) {
+    if (id != fingers[fingerIndex]) {
+      fingers[fingerIndex] = id;
+      lastChangeDate = Msg.getClock();
+    }
+  }
 }