1 /* Copyright (c) 2010-2023. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 #include "s4u-dht-chord.hpp"
8 XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(s4u_chord);
9 namespace sg4 = simgrid::s4u;
11 /* Returns whether an id belongs to the interval [start, end].
13 * The parameters are normalized to make sure they are between 0 and nb_keys - 1).
14 * 1 belongs to [62, 3]
15 * 1 does not belong to [3, 62]
16 * 63 belongs to [62, 3]
17 * 63 does not belong to [3, 62]
18 * 24 belongs to [21, 29]
19 * 24 does not belong to [29, 21]
21 * @param id id to check
22 * @param start lower bound
23 * @param end upper bound
24 * @return true if id in in [start, end]
26 static bool is_in_interval(int id, int start, int end)
29 int s = start % nb_keys;
30 int e = end % nb_keys;
32 // make sure end >= start and id >= start
44 void ChordMessage::destroy(void* message)
46 delete static_cast<ChordMessage*>(message);
49 /* Initializes the current node as the first one of the system */
50 Node::Node(std::vector<std::string> args)
52 xbt_assert(args.size() == 3 || args.size() == 5, "Wrong number of arguments for this node");
55 id_ = std::stoi(args[1]);
56 XBT_DEBUG("Initialize node with id: %d", id_);
58 mailbox_ = sg4::Mailbox::by_name(std::to_string(id_));
59 next_finger_to_fix = 0;
60 fingers_.resize(nb_bits, id_);
62 if (args.size() == 3) { // first ring
63 deadline_ = std::stod(args[2]);
64 start_time_ = sg4::Engine::get_clock();
65 XBT_DEBUG("Create a new Chord ring...");
67 known_id_ = std::stoi(args[2]);
68 start_time_ = std::stod(args[3]);
69 deadline_ = std::stod(args[4]);
70 XBT_DEBUG("Hey! Let's join the system in %f seconds (shall leave at time %f)", start_time_,
71 start_time_ + deadline_);
75 /* Makes the current node join the ring, knowing the id of a node already in the ring
77 * @param known_id id of a node already in the ring
78 * @return true if the join operation succeeded
81 void Node::join(int known_id)
83 XBT_INFO("Joining the ring with id %d, knowing node %d", id_, known_id);
84 setPredecessor(-1); // no predecessor (yet)
86 int successor_id = remoteFindSuccessor(known_id, id_);
87 if (successor_id == -1) {
88 XBT_INFO("Cannot join the ring.");
90 setFinger(0, successor_id);
96 /* Makes the current node quit the system */
99 XBT_INFO("Well Guys! I Think it's time for me to leave ;)");
104 /* Notifies the successor and the predecessor of the current node before leaving */
105 void Node::notifyAndQuit()
107 // send the PREDECESSOR_LEAVING to our successor
108 auto* pred_msg = new ChordMessage(MessageType::PREDECESSOR_LEAVING);
109 pred_msg->request_id = pred_id_;
110 pred_msg->answer_to = mailbox_;
112 XBT_DEBUG("Sending a 'PREDECESSOR_LEAVING' to my successor %d", fingers_[0]);
114 sg4::Mailbox::by_name(std::to_string(fingers_[0]))->put(pred_msg, 10, timeout);
115 } catch (const simgrid::TimeoutException&) {
116 XBT_DEBUG("Timeout expired when sending a 'PREDECESSOR_LEAVING' to my successor %d", fingers_[0]);
120 if (pred_id_ != -1 && pred_id_ != id_) {
121 // send the SUCCESSOR_LEAVING to our predecessor (only if I have one that is not me)
122 auto* succ_msg = new ChordMessage(MessageType::SUCCESSOR_LEAVING);
123 succ_msg->request_id = fingers_[0];
124 succ_msg->answer_to = mailbox_;
125 XBT_DEBUG("Sending a 'SUCCESSOR_LEAVING' to my predecessor %d", pred_id_);
128 sg4::Mailbox::by_name(std::to_string(pred_id_))->put(succ_msg, 10, timeout);
129 } catch (const simgrid::TimeoutException&) {
130 XBT_DEBUG("Timeout expired when sending a 'SUCCESSOR_LEAVING' to my predecessor %d", pred_id_);
136 /* Performs a find successor request to a random id */
137 void Node::randomLookup()
140 int random_index = random.uniform_int(0, nb_bits - 1);
141 int random_id = fingers_[random_index];
142 XBT_DEBUG("Making a lookup request for id %d", random_id);
143 if (random_id != id_)
144 res = findSuccessor(random_id);
145 XBT_DEBUG("The successor of node %d is %d", random_id, res);
148 /* Sets a finger of the current node.
150 * @param node the current node
151 * @param finger_index index of the finger to set (0 to nb_bits - 1)
152 * @param id the id to set for this finger
154 void Node::setFinger(int finger_index, int id)
156 if (id != fingers_[finger_index]) {
157 fingers_[finger_index] = id;
158 XBT_VERB("My new finger #%d is %d", finger_index, id);
162 /* Sets the predecessor of the current node.
163 * @param id the id to predecessor, or -1 to unset the predecessor
165 void Node::setPredecessor(int predecessor_id)
167 if (predecessor_id != pred_id_) {
168 pred_id_ = predecessor_id;
169 XBT_VERB("My new predecessor is %d", predecessor_id);
173 /** refreshes the finger table of the current node (called periodically) */
174 void Node::fixFingers()
176 XBT_DEBUG("Fixing fingers");
177 int id = findSuccessor(id_ + (1U << next_finger_to_fix));
179 if (id != fingers_[next_finger_to_fix]) {
180 setFinger(next_finger_to_fix, id);
183 next_finger_to_fix = (next_finger_to_fix + 1) % nb_bits;
187 /** Displays the finger table of a node. */
188 void Node::printFingerTable()
190 if (XBT_LOG_ISENABLED(s4u_chord, xbt_log_priority_verbose)) {
191 XBT_VERB("My finger table:");
192 XBT_VERB("Start | Succ");
193 for (int i = 0; i < nb_bits; i++) {
194 XBT_VERB(" %3u | %3d", (id_ + (1U << i)) % nb_keys, fingers_[i]);
197 XBT_VERB("Predecessor: %d", pred_id_);
201 /* checks whether the predecessor has failed (called periodically) */
202 void Node::checkPredecessor()
204 XBT_DEBUG("Checking whether my predecessor is alive");
208 sg4::Mailbox* mailbox = sg4::Mailbox::by_name(std::to_string(pred_id_));
209 sg4::Mailbox* return_mailbox = sg4::Mailbox::by_name(std::to_string(id_) + "_is_alive");
211 auto* message = new ChordMessage(MessageType::PREDECESSOR_ALIVE);
212 message->request_id = pred_id_;
213 message->answer_to = return_mailbox;
215 XBT_DEBUG("Sending a 'Predecessor Alive' request to my predecessor %d", pred_id_);
217 mailbox->put(message, 10, timeout);
218 } catch (const simgrid::TimeoutException&) {
219 XBT_DEBUG("Failed to send the 'Predecessor Alive' request to %d", pred_id_);
224 // receive the answer
225 XBT_DEBUG("Sent 'Predecessor Alive' request to %d, waiting for the answer on my mailbox '%s'", pred_id_,
226 message->answer_to->get_cname());
227 ChordMessage* answer = nullptr;
228 sg4::CommPtr comm = return_mailbox->get_async<ChordMessage>(&answer);
231 comm->wait_for(timeout);
232 XBT_DEBUG("Received the answer to my 'Predecessor Alive': my predecessor %d is alive", pred_id_);
234 } catch (const simgrid::TimeoutException&) {
235 XBT_DEBUG("Failed to receive the answer to my 'Predecessor Alive' request");
240 /* Asks its predecessor to a remote node
242 * @param ask_to the node to ask to
243 * @return the id of its predecessor node, or -1 if the request failed (or if the node does not know its predecessor)
245 int Node::remoteGetPredecessor(int ask_to)
247 int predecessor_id = -1;
248 sg4::Mailbox* mailbox = sg4::Mailbox::by_name(std::to_string(ask_to));
249 sg4::Mailbox* return_mailbox = sg4::Mailbox::by_name(std::to_string(id_) + "_pred");
251 auto* message = new ChordMessage(MessageType::GET_PREDECESSOR);
252 message->request_id = id_;
253 message->answer_to = return_mailbox;
255 // send a "Get Predecessor" request to ask_to_id
256 XBT_DEBUG("Sending a 'Get Predecessor' request to %d", ask_to);
258 mailbox->put(message, 10, timeout);
259 } catch (const simgrid::TimeoutException&) {
260 XBT_DEBUG("Failed to send the 'Get Predecessor' request to %d", ask_to);
262 return predecessor_id;
265 // receive the answer
266 XBT_DEBUG("Sent 'Get Predecessor' request to %d, waiting for the answer on my mailbox '%s'", ask_to,
267 message->answer_to->get_cname());
268 ChordMessage* answer = nullptr;
269 sg4::CommPtr comm = return_mailbox->get_async<ChordMessage>(&answer);
272 comm->wait_for(timeout);
273 XBT_DEBUG("Received the answer to my 'Get Predecessor' request: the predecessor of node %d is %d", ask_to,
275 predecessor_id = answer->answer_id;
277 } catch (const simgrid::TimeoutException&) {
278 XBT_DEBUG("Failed to receive the answer to my 'Get Predecessor' request");
282 return predecessor_id;
285 /* Returns the closest preceding finger of an id with respect to the finger table of the current node.
287 * @param id the id to find
288 * @return the closest preceding finger of that id
290 int Node::closestPrecedingFinger(int id)
292 for (int i = nb_bits - 1; i >= 0; i--) {
293 if (is_in_interval(fingers_[i], id_ + 1, id - 1)) {
300 /* Makes the current node find the successor node of an id.
302 * @param id the id to find
303 * @return the id of the successor node, or -1 if the request failed
305 int Node::findSuccessor(int id)
307 // is my successor the successor?
308 if (is_in_interval(id, id_ + 1, fingers_[0])) {
312 // otherwise, ask the closest preceding finger in my table
313 return remoteFindSuccessor(closestPrecedingFinger(id), id);
316 int Node::remoteFindSuccessor(int ask_to, int id)
319 sg4::Mailbox* mailbox = sg4::Mailbox::by_name(std::to_string(ask_to));
320 sg4::Mailbox* return_mailbox = sg4::Mailbox::by_name(std::to_string(id_) + "_succ");
322 auto* message = new ChordMessage(MessageType::FIND_SUCCESSOR);
323 message->request_id = id_;
324 message->answer_to = return_mailbox;
326 // send a "Find Successor" request to ask_to_id
327 XBT_DEBUG("Sending a 'Find Successor' request to %d for id %d", ask_to, id);
329 mailbox->put(message, 10, timeout);
330 } catch (const simgrid::TimeoutException&) {
331 XBT_DEBUG("Failed to send the 'Find Successor' request to %d for id %d", ask_to, id_);
335 // receive the answer
336 XBT_DEBUG("Sent a 'Find Successor' request to %d for key %d, waiting for the answer", ask_to, id);
337 ChordMessage* answer = nullptr;
338 sg4::CommPtr comm = return_mailbox->get_async<ChordMessage>(&answer);
341 comm->wait_for(timeout);
342 XBT_DEBUG("Received the answer to my 'Find Successor' request for id %d: the successor of key %d is %d",
343 answer->request_id, id_, answer->answer_id);
344 successor = answer->answer_id;
346 } catch (const simgrid::TimeoutException&) {
347 XBT_DEBUG("Failed to receive the answer to my 'Find Successor' request");
354 /* Notifies the current node that its predecessor may have changed. */
355 void Node::notify(int predecessor_candidate_id)
357 if (pred_id_ == -1 || is_in_interval(predecessor_candidate_id, pred_id_ + 1, id_ - 1)) {
358 setPredecessor(predecessor_candidate_id);
361 XBT_DEBUG("I don't have to change my predecessor to %d", predecessor_candidate_id);
365 /* Notifies a remote node that its predecessor may have changed. */
366 void Node::remoteNotify(int notify_id, int predecessor_candidate_id) const
368 auto* message = new ChordMessage(MessageType::NOTIFY);
369 message->request_id = predecessor_candidate_id;
370 message->answer_to = nullptr;
372 // send a "Notify" request to notify_id
373 XBT_DEBUG("Sending a 'Notify' request to %d", notify_id);
374 sg4::Mailbox* mailbox = sg4::Mailbox::by_name(std::to_string(notify_id));
375 mailbox->put_init(message, 10)->detach(ChordMessage::destroy);
378 /* This function is called periodically. It checks the immediate successor of the current node. */
379 void Node::stabilize()
381 XBT_DEBUG("Stabilizing node");
383 // get the predecessor of my immediate successor
384 int candidate_id = pred_id_;
385 int successor_id = fingers_[0];
386 if (successor_id != id_)
387 candidate_id = remoteGetPredecessor(successor_id);
389 // this node is a candidate to become my new successor
390 if (candidate_id != -1 && is_in_interval(candidate_id, id_ + 1, successor_id - 1)) {
391 setFinger(0, candidate_id);
393 if (successor_id != id_) {
394 remoteNotify(successor_id, id_);
398 /* This function is called when a node receives a message.
400 * @param message the message to handle (don't touch it afterward: it will be destroyed, reused or forwarded)
402 void Node::handleMessage(ChordMessage* message)
404 switch (message->type) {
405 case MessageType::FIND_SUCCESSOR:
406 XBT_DEBUG("Received a 'Find Successor' request from %s for id %d", message->issuer_host_name.c_str(),
407 message->request_id);
408 // is my successor the successor?
409 if (is_in_interval(message->request_id, id_ + 1, fingers_[0])) {
410 message->type = MessageType::FIND_SUCCESSOR_ANSWER;
411 message->answer_id = fingers_[0];
412 XBT_DEBUG("Sending back a 'Find Successor Answer' to %s (mailbox %s): the successor of %d is %d",
413 message->issuer_host_name.c_str(), message->answer_to->get_cname(), message->request_id,
415 message->answer_to->put_init(message, 10)->detach(ChordMessage::destroy);
417 // otherwise, forward the request to the closest preceding finger in my table
418 int closest = closestPrecedingFinger(message->request_id);
419 XBT_DEBUG("Forwarding the 'Find Successor' request for id %d to my closest preceding finger %d",
420 message->request_id, closest);
421 sg4::Mailbox* mailbox = sg4::Mailbox::by_name(std::to_string(closest));
422 mailbox->put_init(message, 10)->detach(ChordMessage::destroy);
426 case MessageType::GET_PREDECESSOR:
427 XBT_DEBUG("Receiving a 'Get Predecessor' request from %s", message->issuer_host_name.c_str());
428 message->type = MessageType::GET_PREDECESSOR_ANSWER;
429 message->answer_id = pred_id_;
430 XBT_DEBUG("Sending back a 'Get Predecessor Answer' to %s via mailbox '%s': my predecessor is %d",
431 message->issuer_host_name.c_str(), message->answer_to->get_cname(), message->answer_id);
432 message->answer_to->put_init(message, 10)->detach(ChordMessage::destroy);
435 case MessageType::NOTIFY:
436 // someone is telling me that he may be my new predecessor
437 XBT_DEBUG("Receiving a 'Notify' request from %s", message->issuer_host_name.c_str());
438 notify(message->request_id);
442 case MessageType::PREDECESSOR_LEAVING:
443 // my predecessor is about to quit
444 XBT_DEBUG("Receiving a 'Predecessor Leaving' message from %s", message->issuer_host_name.c_str());
445 // modify my predecessor
446 setPredecessor(message->request_id);
449 >> notify my new predecessor
450 >> send a notify_predecessors !!
454 case MessageType::SUCCESSOR_LEAVING:
455 // my successor is about to quit
456 XBT_DEBUG("Receiving a 'Successor Leaving' message from %s", message->issuer_host_name.c_str());
457 // modify my successor FIXME : this should be implicit ?
458 setFinger(0, message->request_id);
461 >> notify my new successor
462 >> update my table & predecessors table */
465 case MessageType::PREDECESSOR_ALIVE:
466 XBT_DEBUG("Receiving a 'Predecessor Alive' request from %s", message->issuer_host_name.c_str());
467 message->type = MessageType::PREDECESSOR_ALIVE_ANSWER;
468 XBT_DEBUG("Sending back a 'Predecessor Alive Answer' to %s (mailbox %s)", message->issuer_host_name.c_str(),
469 message->answer_to->get_cname());
470 message->answer_to->put_init(message, 10)->detach(ChordMessage::destroy);
474 XBT_DEBUG("Ignoring unexpected message: %d from %s", static_cast<int>(message->type),
475 message->issuer_host_name.c_str());
480 void Node::operator()()
482 sg4::this_actor::sleep_for(start_time_);
483 if (known_id_ == -1) {
484 setPredecessor(-1); // -1 means that I have no predecessor
493 ChordMessage* message = nullptr;
494 double now = sg4::Engine::get_clock();
495 double next_stabilize_date = start_time_ + PERIODIC_STABILIZE_DELAY;
496 double next_fix_fingers_date = start_time_ + PERIODIC_FIX_FINGERS_DELAY;
497 double next_check_predecessor_date = start_time_ + PERIODIC_CHECK_PREDECESSOR_DELAY;
498 double next_lookup_date = start_time_ + PERIODIC_LOOKUP_DELAY;
499 sg4::CommPtr comm_receive = nullptr;
500 while (now < std::min(start_time_ + deadline_, MAX_SIMULATION_TIME)) {
501 if (comm_receive == nullptr)
502 comm_receive = mailbox_->get_async<ChordMessage>(&message);
503 bool comm_completed = true;
505 if (not comm_receive->test())
506 comm_completed = false;
507 } catch (const simgrid::TimeoutException&) {
508 XBT_DEBUG("Caught a timeout, go ahead.");
511 if (comm_completed) {
512 if (message != nullptr) {
513 handleMessage(message);
516 comm_receive = nullptr;
518 // no task was received: make some periodic calls
519 if (now >= next_stabilize_date) {
521 next_stabilize_date = sg4::Engine::get_clock() + PERIODIC_STABILIZE_DELAY;
522 } else if (now >= next_fix_fingers_date) {
524 next_fix_fingers_date = sg4::Engine::get_clock() + PERIODIC_FIX_FINGERS_DELAY;
525 } else if (now >= next_check_predecessor_date) {
527 next_check_predecessor_date = sg4::Engine::get_clock() + PERIODIC_CHECK_PREDECESSOR_DELAY;
528 } else if (now >= next_lookup_date) {
530 next_lookup_date = sg4::Engine::get_clock() + PERIODIC_LOOKUP_DELAY;
532 // nothing to do: sleep for a while
533 sg4::this_actor::sleep_for(SLEEP_DELAY);
537 now = sg4::Engine::get_clock();
539 if (comm_receive != nullptr) {
541 if (comm_receive->test())
544 comm_receive->cancel();
545 } catch (const simgrid::TimeoutException&) {
546 XBT_DEBUG("Caught a timeout for last message, nevermind.");