+++ /dev/null
-/* Copyright (c) 2006-2020. The SimGrid Team. All rights reserved. */
-
-/* This program is free software; you can redistribute it and/or modify it
- * under the terms of the license (GNU LGPL) which comes with this package. */
-
-package dht.chord;
-
-import org.simgrid.msg.Msg;
-import org.simgrid.msg.Comm;
-import org.simgrid.msg.Host;
-import org.simgrid.msg.Task;
-import org.simgrid.msg.Process;
-import org.simgrid.msg.MsgException;
-import org.simgrid.msg.TimeoutException;
-public class Node extends Process {
- 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;
- private 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;
- 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;
-
- mailbox = args[0];
- id = Integer.parseInt(args[0]);
-
- 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.parseInt(args[1]);
- create();
- joinSuccess = true;
- } else {
- int knownId = Integer.parseInt(args[1]);
- deadline = Integer.parseInt(args[3]);
- Msg.debug("Hey! Let's join the system with the id " + id + ".");
-
- joinSuccess = join(knownId);
- }
-
- if (!joinSuccess) {
- Msg.info("I couldn't join the ring");
- return;
- }
-
- 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;
- }
- }
-
- private void handleTask(Task task) {
- if (task instanceof FindSuccessorTask) {
- FindSuccessorTask fTask = (FindSuccessorTask)task;
- Msg.debug("Receiving a 'Find Successor' request from " + fTask.getIssuerHostName() + " for id " +
- fTask.getRequestId());
- // is my successor the successor?
- if (isInInterval(fTask.getRequestId(), this.id + 1, fingers[0])) {
- Msg.debug("Send the request to " + fTask.getAnswerTo() + " with answer " + fingers[0]);
- FindSuccessorAnswerTask answer = new FindSuccessorAnswerTask(getHost().getName(), mailbox, fingers[0]);
- answer.dsend(fTask.getAnswerTo());
- } else {
- // otherwise, forward the request to the closest preceding finger in my table
- int closest = closestPrecedingNode(fTask.getRequestId());
- Msg.debug("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.getIssuerHostName());
- GetPredecessorAnswerTask answer = new GetPredecessorAnswerTask(getHost().getName(), mailbox, predId);
- answer.dsend(gTask.getAnswerTo());
- } else if (task instanceof NotifyTask) {
- NotifyTask nTask = (NotifyTask)task;
- notify(nTask.getRequestId());
- } else {
- Msg.debug("Ignoring unexpected task of type:" + task);
- }
- }
-
- private void leave() {
- Msg.debug("Well Guys! I Think it's time for me to quit ;)");
- // TODO: Notify my successor and predecessor.
- }
-
- /** @brief Initializes the current node as the first one of the system */
- private 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
- private 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;
- }
-
- private 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)
- */
- private 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);
- do {
- if (commReceive == null) {
- commReceive = Task.irecv(this.mailbox);
- }
- commReceive.waitCompletion(Common.TIMEOUT);
- Task taskReceived = commReceive.getTask();
- if (taskReceived instanceof GetPredecessorAnswerTask) {
- predecessorId = ((GetPredecessorAnswerTask) taskReceived).getAnswerId();
- stop = true;
- } else {
- handleTask(taskReceived);
- }
- commReceive = null;
- } while (!stop);
- }
- catch (MsgException e) {
- Msg.debug("Failed to send the Get Predecessor request");
- }
- commReceive = null;
-
- 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
- */
- private 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.
- private int remoteFindSuccessor(int askTo, int id) {
- int successor = -1;
- boolean stop = false;
- String askToMailbox = Integer.toString(askTo);
- Task sendTask = new FindSuccessorTask(getHost().getName(), this.mailbox, id);
- Msg.debug("Sending a 'Find Successor' request to " + askToMailbox + " for id " + id);
- try {
- sendTask.send(askToMailbox, Common.TIMEOUT);
- do {
- if (commReceive == null) {
- commReceive = Task.irecv(this.mailbox);
- }
- 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.getAnswerId();
- } else {
- handleTask(task);
- }
- 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");
- }
- commReceive = null;
-
- return successor;
- }
-
- // This function is called periodically. It checks the immediate successor of the current node.
- private 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
- */
- private 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
- */
- private 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.
- private void fixFingers() {
- Msg.debug("Fixing fingers");
- int successorId = findSuccessor(id + (1 << nextFingerToFix));
- if (successorId != -1) {
- if (successorId != fingers[nextFingerToFix]) {
- setFinger(nextFingerToFix, successorId);
- }
- nextFingerToFix = (nextFingerToFix + 1) % Common.NB_BITS;
- }
- }
-
- // This function is called periodically.
- // It checks whether the predecessor has failed
- private void checkPredecessor() {
- //TODO
- }
-
- // Performs a find successor request to a random id.
- private void randomLookup() {
- int dest = 1337;
- findSuccessor(dest);
- }
-
- /**
- * @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
- */
- private int closestPrecedingNode(int id) {
- for (int 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]
- */
- private static boolean isInInterval(int id, int start, int end) {
- int normId = normalize(id);
- int normStart = normalize(start);
- int normEnd = normalize(end);
-
- // make sure end >= start and id >= start
- if (normEnd < normStart) {
- normEnd += Common.NB_KEYS;
- }
- if (normId < normStart) {
- normId += Common.NB_KEYS;
- }
- return (normId <= normEnd);
- }
-
- /**
- * @brief Turns an id into an equivalent id in [0, nb_keys).
- * @param id an id
- * @return the corresponding normalized id
- */
- private 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
- */
- private void setFinger(int fingerIndex, int id) {
- if (id != fingers[fingerIndex]) {
- fingers[fingerIndex] = id;
- lastChangeDate = Msg.getClock();
- }
- }
-}
