--- /dev/null
+/* Copyright (c) 2010-2021. 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. */
+
+#include "s4u-dht-chord.hpp"
+
+XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(s4u_chord);
+
+/* Returns whether an id belongs to the interval [start, end].
+ *
+ * The parameters are normalized 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 true if id in in [start, end]
+ */
+static bool is_in_interval(int id, int start, int end)
+{
+ int i = id % nb_keys;
+ int s = start % nb_keys;
+ int e = end % nb_keys;
+
+ // make sure end >= start and id >= start
+ if (e < s) {
+ e += nb_keys;
+ }
+
+ if (i < s) {
+ i += nb_keys;
+ }
+
+ return i <= e;
+}
+
+void ChordMessage::destroy(void* message)
+{
+ delete static_cast<ChordMessage*>(message);
+}
+
+/* Initializes the current node as the first one of the system */
+Node::Node(std::vector<std::string> args)
+{
+ xbt_assert(args.size() == 3 || args.size() == 5, "Wrong number of arguments for this node");
+
+ // initialize my node
+ id_ = std::stoi(args[1]);
+ XBT_DEBUG("Initialize node with id: %d", id_);
+ random.set_seed(id_);
+ mailbox_ = simgrid::s4u::Mailbox::by_name(std::to_string(id_));
+ next_finger_to_fix = 0;
+ fingers_.resize(nb_bits, id_);
+
+ if (args.size() == 3) { // first ring
+ deadline_ = std::stod(args[2]);
+ start_time_ = simgrid::s4u::Engine::get_clock();
+ XBT_DEBUG("Create a new Chord ring...");
+ } else {
+ known_id_ = std::stoi(args[2]);
+ start_time_ = std::stod(args[3]);
+ deadline_ = std::stod(args[4]);
+ XBT_DEBUG("Hey! Let's join the system in %f seconds (shall leave at time %f)", start_time_,
+ start_time_ + deadline_);
+ }
+}
+
+/* Makes the current node join the ring, knowing the id of a node already in the ring
+ *
+ * @param known_id id of a node already in the ring
+ * @return true if the join operation succeeded
+ * */
+
+void Node::join(int known_id)
+{
+ XBT_INFO("Joining the ring with id %d, knowing node %d", id_, known_id);
+ setPredecessor(-1); // no predecessor (yet)
+
+ int successor_id = remoteFindSuccessor(known_id, id_);
+ if (successor_id == -1) {
+ XBT_INFO("Cannot join the ring.");
+ } else {
+ setFinger(0, successor_id);
+ printFingerTable();
+ joined = true;
+ }
+}
+
+/* Makes the current node quit the system */
+void Node::leave()
+{
+ XBT_INFO("Well Guys! I Think it's time for me to leave ;)");
+ notifyAndQuit();
+ joined = false;
+}
+
+/* Notifies the successor and the predecessor of the current node before leaving */
+void Node::notifyAndQuit()
+{
+ // send the PREDECESSOR_LEAVING to our successor
+ auto* pred_msg = new ChordMessage(MessageType::PREDECESSOR_LEAVING);
+ pred_msg->request_id = pred_id_;
+ pred_msg->answer_to = mailbox_;
+
+ XBT_DEBUG("Sending a 'PREDECESSOR_LEAVING' to my successor %d", fingers_[0]);
+ try {
+ simgrid::s4u::Mailbox::by_name(std::to_string(fingers_[0]))->put(pred_msg, 10, timeout);
+ } catch (const simgrid::TimeoutException&) {
+ XBT_DEBUG("Timeout expired when sending a 'PREDECESSOR_LEAVING' to my successor %d", fingers_[0]);
+ delete pred_msg;
+ }
+
+ if (pred_id_ != -1 && pred_id_ != id_) {
+ // send the SUCCESSOR_LEAVING to our predecessor (only if I have one that is not me)
+ auto* succ_msg = new ChordMessage(MessageType::SUCCESSOR_LEAVING);
+ succ_msg->request_id = fingers_[0];
+ succ_msg->answer_to = mailbox_;
+ XBT_DEBUG("Sending a 'SUCCESSOR_LEAVING' to my predecessor %d", pred_id_);
+
+ try {
+ simgrid::s4u::Mailbox::by_name(std::to_string(pred_id_))->put(succ_msg, 10, timeout);
+ } catch (const simgrid::TimeoutException&) {
+ XBT_DEBUG("Timeout expired when sending a 'SUCCESSOR_LEAVING' to my predecessor %d", pred_id_);
+ delete succ_msg;
+ }
+ }
+}
+
+/* Performs a find successor request to a random id */
+void Node::randomLookup()
+{
+ int res = id_;
+ int random_index = random.uniform_int(0, nb_bits - 1);
+ int random_id = fingers_[random_index];
+ XBT_DEBUG("Making a lookup request for id %d", random_id);
+ if (random_id != id_)
+ res = findSuccessor(random_id);
+ XBT_DEBUG("The successor of node %d is %d", random_id, res);
+}
+
+/* Sets a finger of the current node.
+ *
+ * @param node 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 Node::setFinger(int finger_index, int id)
+{
+ if (id != fingers_[finger_index]) {
+ fingers_[finger_index] = id;
+ XBT_VERB("My new finger #%d is %d", finger_index, id);
+ }
+}
+
+/* Sets the predecessor of the current node.
+ * @param id the id to predecessor, or -1 to unset the predecessor
+ */
+void Node::setPredecessor(int predecessor_id)
+{
+ if (predecessor_id != pred_id_) {
+ pred_id_ = predecessor_id;
+ XBT_VERB("My new predecessor is %d", predecessor_id);
+ }
+}
+
+/** refreshes the finger table of the current node (called periodically) */
+void Node::fixFingers()
+{
+ XBT_DEBUG("Fixing fingers");
+ int id = findSuccessor(id_ + (1U << next_finger_to_fix));
+ if (id != -1) {
+ if (id != fingers_[next_finger_to_fix]) {
+ setFinger(next_finger_to_fix, id);
+ printFingerTable();
+ }
+ next_finger_to_fix = (next_finger_to_fix + 1) % nb_bits;
+ }
+}
+
+/** Displays the finger table of a node. */
+void Node::printFingerTable()
+{
+ if (XBT_LOG_ISENABLED(s4u_chord, xbt_log_priority_verbose)) {
+ XBT_VERB("My finger table:");
+ XBT_VERB("Start | Succ");
+ for (int i = 0; i < nb_bits; i++) {
+ XBT_VERB(" %3u | %3d", (id_ + (1U << i)) % nb_keys, fingers_[i]);
+ }
+
+ XBT_VERB("Predecessor: %d", pred_id_);
+ }
+}
+
+/* checks whether the predecessor has failed (called periodically) */
+void Node::checkPredecessor()
+{
+ XBT_DEBUG("Checking whether my predecessor is alive");
+ if (pred_id_ == -1)
+ return;
+
+ simgrid::s4u::Mailbox* mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(pred_id_));
+ simgrid::s4u::Mailbox* return_mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(id_) + "_is_alive");
+
+ auto* message = new ChordMessage(MessageType::PREDECESSOR_ALIVE);
+ message->request_id = pred_id_;
+ message->answer_to = return_mailbox;
+
+ XBT_DEBUG("Sending a 'Predecessor Alive' request to my predecessor %d", pred_id_);
+ try {
+ mailbox->put(message, 10, timeout);
+ } catch (const simgrid::TimeoutException&) {
+ XBT_DEBUG("Failed to send the 'Predecessor Alive' request to %d", pred_id_);
+ delete message;
+ return;
+ }
+
+ // receive the answer
+ XBT_DEBUG("Sent 'Predecessor Alive' request to %d, waiting for the answer on my mailbox '%s'", pred_id_,
+ message->answer_to->get_cname());
+ ChordMessage* answer = nullptr;
+ simgrid::s4u::CommPtr comm = return_mailbox->get_async<ChordMessage>(&answer);
+
+ try {
+ comm->wait_for(timeout);
+ XBT_DEBUG("Received the answer to my 'Predecessor Alive': my predecessor %d is alive", pred_id_);
+ delete answer;
+ } catch (const simgrid::TimeoutException&) {
+ XBT_DEBUG("Failed to receive the answer to my 'Predecessor Alive' request");
+ pred_id_ = -1;
+ }
+}
+
+/* Asks its predecessor to a remote node
+ *
+ * @param ask_to 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 Node::remoteGetPredecessor(int ask_to)
+{
+ int predecessor_id = -1;
+ simgrid::s4u::Mailbox* mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(ask_to));
+ simgrid::s4u::Mailbox* return_mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(id_) + "_pred");
+
+ auto* message = new ChordMessage(MessageType::GET_PREDECESSOR);
+ message->request_id = id_;
+ message->answer_to = return_mailbox;
+
+ // send a "Get Predecessor" request to ask_to_id
+ XBT_DEBUG("Sending a 'Get Predecessor' request to %d", ask_to);
+ try {
+ mailbox->put(message, 10, timeout);
+ } catch (const simgrid::TimeoutException&) {
+ XBT_DEBUG("Failed to send the 'Get Predecessor' request to %d", ask_to);
+ delete message;
+ return predecessor_id;
+ }
+
+ // receive the answer
+ XBT_DEBUG("Sent 'Get Predecessor' request to %d, waiting for the answer on my mailbox '%s'", ask_to,
+ message->answer_to->get_cname());
+ ChordMessage* answer = nullptr;
+ simgrid::s4u::CommPtr comm = return_mailbox->get_async<ChordMessage>(&answer);
+
+ try {
+ comm->wait_for(timeout);
+ XBT_DEBUG("Received the answer to my 'Get Predecessor' request: the predecessor of node %d is %d", ask_to,
+ answer->answer_id);
+ predecessor_id = answer->answer_id;
+ delete answer;
+ } catch (const simgrid::TimeoutException&) {
+ XBT_DEBUG("Failed to receive the answer to my 'Get Predecessor' request");
+ delete answer;
+ }
+
+ return predecessor_id;
+}
+
+/* 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 Node::closestPrecedingFinger(int id)
+{
+ for (int i = nb_bits - 1; i >= 0; i--) {
+ if (is_in_interval(fingers_[i], id_ + 1, id - 1)) {
+ return fingers_[i];
+ }
+ }
+ return id_;
+}
+
+/* Makes the current node find the successor node of an id.
+ *
+ * @param id the id to find
+ * @return the id of the successor node, or -1 if the request failed
+ */
+int Node::findSuccessor(int id)
+{
+ // is my successor the successor?
+ if (is_in_interval(id, id_ + 1, fingers_[0])) {
+ return fingers_[0];
+ }
+
+ // otherwise, ask the closest preceding finger in my table
+ return remoteFindSuccessor(closestPrecedingFinger(id), id);
+}
+
+int Node::remoteFindSuccessor(int ask_to, int id)
+{
+ int successor = -1;
+ simgrid::s4u::Mailbox* mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(ask_to));
+ simgrid::s4u::Mailbox* return_mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(id_) + "_succ");
+
+ auto* message = new ChordMessage(MessageType::FIND_SUCCESSOR);
+ message->request_id = id_;
+ message->answer_to = return_mailbox;
+
+ // send a "Find Successor" request to ask_to_id
+ XBT_DEBUG("Sending a 'Find Successor' request to %d for id %d", ask_to, id);
+ try {
+ mailbox->put(message, 10, timeout);
+ } catch (const simgrid::TimeoutException&) {
+ XBT_DEBUG("Failed to send the 'Find Successor' request to %d for id %d", ask_to, id_);
+ delete message;
+ return successor;
+ }
+ // receive the answer
+ XBT_DEBUG("Sent a 'Find Successor' request to %d for key %d, waiting for the answer", ask_to, id);
+ ChordMessage* answer = nullptr;
+ simgrid::s4u::CommPtr comm = return_mailbox->get_async<ChordMessage>(&answer);
+
+ try {
+ comm->wait_for(timeout);
+ XBT_DEBUG("Received the answer to my 'Find Successor' request for id %d: the successor of key %d is %d",
+ answer->request_id, id_, answer->answer_id);
+ successor = answer->answer_id;
+ delete answer;
+ } catch (const simgrid::TimeoutException&) {
+ XBT_DEBUG("Failed to receive the answer to my 'Find Successor' request");
+ delete answer;
+ }
+
+ return successor;
+}
+
+/* Notifies the current node that its predecessor may have changed. */
+void Node::notify(int predecessor_candidate_id)
+{
+ if (pred_id_ == -1 || is_in_interval(predecessor_candidate_id, pred_id_ + 1, id_ - 1)) {
+ setPredecessor(predecessor_candidate_id);
+ printFingerTable();
+ } else {
+ XBT_DEBUG("I don't have to change my predecessor to %d", predecessor_candidate_id);
+ }
+}
+
+/* Notifies a remote node that its predecessor may have changed. */
+void Node::remoteNotify(int notify_id, int predecessor_candidate_id) const
+{
+ auto* message = new ChordMessage(MessageType::NOTIFY);
+ message->request_id = predecessor_candidate_id;
+ message->answer_to = nullptr;
+
+ // send a "Notify" request to notify_id
+ XBT_DEBUG("Sending a 'Notify' request to %d", notify_id);
+ simgrid::s4u::Mailbox* mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(notify_id));
+ mailbox->put_init(message, 10)->detach(ChordMessage::destroy);
+}
+
+/* This function is called periodically. It checks the immediate successor of the current node. */
+void Node::stabilize()
+{
+ XBT_DEBUG("Stabilizing node");
+
+ // get the predecessor of my immediate successor
+ int candidate_id = pred_id_;
+ int successor_id = fingers_[0];
+ if (successor_id != id_)
+ candidate_id = remoteGetPredecessor(successor_id);
+
+ // this node is a candidate to become my new successor
+ if (candidate_id != -1 && is_in_interval(candidate_id, id_ + 1, successor_id - 1)) {
+ setFinger(0, candidate_id);
+ }
+ if (successor_id != id_) {
+ remoteNotify(successor_id, id_);
+ }
+}
+
+/* This function is called when a node receives a message.
+ *
+ * @param message the message to handle (don't touch it afterward: it will be destroyed, reused or forwarded)
+ */
+void Node::handleMessage(ChordMessage* message)
+{
+ switch (message->type) {
+ case MessageType::FIND_SUCCESSOR:
+ XBT_DEBUG("Received a 'Find Successor' request from %s for id %d", message->issuer_host_name.c_str(),
+ message->request_id);
+ // is my successor the successor?
+ if (is_in_interval(message->request_id, id_ + 1, fingers_[0])) {
+ message->type = MessageType::FIND_SUCCESSOR_ANSWER;
+ message->answer_id = fingers_[0];
+ XBT_DEBUG("Sending back a 'Find Successor Answer' to %s (mailbox %s): the successor of %d is %d",
+ message->issuer_host_name.c_str(), message->answer_to->get_cname(), message->request_id,
+ message->answer_id);
+ message->answer_to->put_init(message, 10)->detach(ChordMessage::destroy);
+ } else {
+ // otherwise, forward the request to the closest preceding finger in my table
+ int closest = closestPrecedingFinger(message->request_id);
+ XBT_DEBUG("Forwarding the 'Find Successor' request for id %d to my closest preceding finger %d",
+ message->request_id, closest);
+ simgrid::s4u::Mailbox* mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(closest));
+ mailbox->put_init(message, 10)->detach(ChordMessage::destroy);
+ }
+ break;
+
+ case MessageType::GET_PREDECESSOR:
+ XBT_DEBUG("Receiving a 'Get Predecessor' request from %s", message->issuer_host_name.c_str());
+ message->type = MessageType::GET_PREDECESSOR_ANSWER;
+ message->answer_id = pred_id_;
+ XBT_DEBUG("Sending back a 'Get Predecessor Answer' to %s via mailbox '%s': my predecessor is %d",
+ message->issuer_host_name.c_str(), message->answer_to->get_cname(), message->answer_id);
+ message->answer_to->put_init(message, 10)->detach(ChordMessage::destroy);
+ break;
+
+ case MessageType::NOTIFY:
+ // someone is telling me that he may be my new predecessor
+ XBT_DEBUG("Receiving a 'Notify' request from %s", message->issuer_host_name.c_str());
+ notify(message->request_id);
+ delete message;
+ break;
+
+ case MessageType::PREDECESSOR_LEAVING:
+ // my predecessor is about to quit
+ XBT_DEBUG("Receiving a 'Predecessor Leaving' message from %s", message->issuer_host_name.c_str());
+ // modify my predecessor
+ setPredecessor(message->request_id);
+ delete message;
+ /*TODO :
+ >> notify my new predecessor
+ >> send a notify_predecessors !!
+ */
+ break;
+
+ case MessageType::SUCCESSOR_LEAVING:
+ // my successor is about to quit
+ XBT_DEBUG("Receiving a 'Successor Leaving' message from %s", message->issuer_host_name.c_str());
+ // modify my successor FIXME : this should be implicit ?
+ setFinger(0, message->request_id);
+ delete message;
+ /* TODO
+ >> notify my new successor
+ >> update my table & predecessors table */
+ break;
+
+ case MessageType::PREDECESSOR_ALIVE:
+ XBT_DEBUG("Receiving a 'Predecessor Alive' request from %s", message->issuer_host_name.c_str());
+ message->type = MessageType::PREDECESSOR_ALIVE_ANSWER;
+ XBT_DEBUG("Sending back a 'Predecessor Alive Answer' to %s (mailbox %s)", message->issuer_host_name.c_str(),
+ message->answer_to->get_cname());
+ message->answer_to->put_init(message, 10)->detach(ChordMessage::destroy);
+ break;
+
+ default:
+ XBT_DEBUG("Ignoring unexpected message: %d from %s", static_cast<int>(message->type),
+ message->issuer_host_name.c_str());
+ delete message;
+ }
+}
+
+void Node::operator()()
+{
+ simgrid::s4u::this_actor::sleep_for(start_time_);
+ if (known_id_ == -1) {
+ setPredecessor(-1); // -1 means that I have no predecessor
+ printFingerTable();
+ joined = true;
+ } else {
+ join(known_id_);
+ }
+
+ if (not joined)
+ return;
+ ChordMessage* message = nullptr;
+ double now = simgrid::s4u::Engine::get_clock();
+ double next_stabilize_date = start_time_ + PERIODIC_STABILIZE_DELAY;
+ double next_fix_fingers_date = start_time_ + PERIODIC_FIX_FINGERS_DELAY;
+ double next_check_predecessor_date = start_time_ + PERIODIC_CHECK_PREDECESSOR_DELAY;
+ double next_lookup_date = start_time_ + PERIODIC_LOOKUP_DELAY;
+ simgrid::s4u::CommPtr comm_receive = nullptr;
+ while (now < std::min(start_time_ + deadline_, MAX_SIMULATION_TIME)) {
+ if (comm_receive == nullptr)
+ comm_receive = mailbox_->get_async<ChordMessage>(&message);
+ bool comm_completed = true;
+ try {
+ if (not comm_receive->test())
+ comm_completed = false;
+ } catch (const simgrid::TimeoutException&) {
+ XBT_DEBUG("Caught a timeout, go ahead.");
+ }
+
+ if (comm_completed) {
+ if (message != nullptr) {
+ handleMessage(message);
+ message = nullptr;
+ }
+ comm_receive = nullptr;
+ } else {
+ // no task was received: make some periodic calls
+ if (now >= next_stabilize_date) {
+ stabilize();
+ next_stabilize_date = simgrid::s4u::Engine::get_clock() + PERIODIC_STABILIZE_DELAY;
+ } else if (now >= next_fix_fingers_date) {
+ fixFingers();
+ next_fix_fingers_date = simgrid::s4u::Engine::get_clock() + PERIODIC_FIX_FINGERS_DELAY;
+ } else if (now >= next_check_predecessor_date) {
+ checkPredecessor();
+ next_check_predecessor_date = simgrid::s4u::Engine::get_clock() + PERIODIC_CHECK_PREDECESSOR_DELAY;
+ } else if (now >= next_lookup_date) {
+ randomLookup();
+ next_lookup_date = simgrid::s4u::Engine::get_clock() + PERIODIC_LOOKUP_DELAY;
+ } else {
+ // nothing to do: sleep for a while
+ simgrid::s4u::this_actor::sleep_for(SLEEP_DELAY);
+ }
+ }
+
+ now = simgrid::s4u::Engine::get_clock();
+ }
+ if (comm_receive != nullptr) {
+ try {
+ if (comm_receive->test())
+ delete message;
+ else
+ comm_receive->cancel();
+ } catch (const simgrid::TimeoutException&) {
+ XBT_DEBUG("Caught a timeout for last message, nevermind.");
+ }
+ }
+ // leave the ring
+ leave();
+}