1 /* Copyright (c) 2010-2018. 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);
10 /* Returns whether an id belongs to the interval [start, end].
12 * The parameters are normalized to make sure they are between 0 and nb_keys - 1).
13 * 1 belongs to [62, 3]
14 * 1 does not belong to [3, 62]
15 * 63 belongs to [62, 3]
16 * 63 does not belong to [3, 62]
17 * 24 belongs to [21, 29]
18 * 24 does not belong to [29, 21]
20 * @param id id to check
21 * @param start lower bound
22 * @param end upper bound
23 * @return a non-zero value if id in in [start, end]
25 static int is_in_interval(int id, int start, int end)
28 int s = start % nb_keys;
29 int e = end % nb_keys;
31 // make sure end >= start and id >= start
43 void ChordMessage::destroy(void* message)
45 delete static_cast<ChordMessage*>(message);
48 /* Initializes the current node as the first one of the system */
49 Node::Node(std::vector<std::string> args)
51 xbt_assert(args.size() == 3 || args.size() == 5, "Wrong number of arguments for this node");
54 id_ = std::stoi(args[1]);
55 stream = simgrid::s4u::this_actor::get_host()->extension<HostChord>()->getStream();
56 mailbox_ = simgrid::s4u::Mailbox::by_name(std::to_string(id_));
57 next_finger_to_fix = 0;
58 fingers_ = new int[nb_bits];
60 for (int i = 0; i < nb_bits; i++) {
64 if (args.size() == 3) { // first ring
65 deadline_ = std::stod(args[2]);
66 start_time_ = simgrid::s4u::Engine::get_clock();
67 XBT_DEBUG("Create a new Chord ring...");
69 known_id_ = std::stoi(args[2]);
70 start_time_ = std::stod(args[3]);
71 deadline_ = std::stod(args[4]);
72 XBT_DEBUG("Hey! Let's join the system in %f seconds (shall leave at time %f)", start_time_,
73 start_time_ + deadline_);
81 /* Makes the current node join the ring, knowing the id of a node already in the ring
83 * @param known_id id of a node already in the ring
84 * @return true if the join operation succeeded
87 void Node::join(int known_id)
89 XBT_INFO("Joining the ring with id %d, knowing node %d", id_, known_id);
90 setPredecessor(-1); // no predecessor (yet)
92 int successor_id = remoteFindSuccessor(known_id, id_);
93 if (successor_id == -1) {
94 XBT_INFO("Cannot join the ring.");
96 setFinger(0, successor_id);
102 /* Makes the current node quit the system */
105 XBT_INFO("Well Guys! I Think it's time for me to leave ;)");
110 /* Notifies the successor and the predecessor of the current node before leaving */
111 void Node::notifyAndQuit()
113 // send the PREDECESSOR_LEAVING to our successor
114 ChordMessage* pred_msg = new ChordMessage(PREDECESSOR_LEAVING);
115 pred_msg->request_id = pred_id_;
116 pred_msg->answer_to = mailbox_;
118 XBT_DEBUG("Sending a 'PREDECESSOR_LEAVING' to my successor %d", fingers_[0]);
120 simgrid::s4u::Mailbox::by_name(std::to_string(fingers_[0]))->put(pred_msg, 10, timeout);
121 } catch (simgrid::TimeoutError& e) {
122 XBT_DEBUG("Timeout expired when sending a 'PREDECESSOR_LEAVING' to my successor %d", fingers_[0]);
126 if (pred_id_ != -1 && pred_id_ != id_) {
127 // send the SUCCESSOR_LEAVING to our predecessor (only if I have one that is not me)
128 ChordMessage* succ_msg = new ChordMessage(SUCCESSOR_LEAVING);
129 succ_msg->request_id = fingers_[0];
130 succ_msg->answer_to = mailbox_;
131 XBT_DEBUG("Sending a 'SUCCESSOR_LEAVING' to my predecessor %d", pred_id_);
134 simgrid::s4u::Mailbox::by_name(std::to_string(pred_id_))->put(succ_msg, 10, timeout);
135 } catch (simgrid::TimeoutError& e) {
136 XBT_DEBUG("Timeout expired when sending a 'SUCCESSOR_LEAVING' to my predecessor %d", pred_id_);
142 /* Performs a find successor request to a random id */
143 void Node::randomLookup()
146 int random_index = RngStream_RandInt(stream, 0, nb_bits - 1);
147 int random_id = fingers_[random_index];
148 XBT_DEBUG("Making a lookup request for id %d", random_id);
149 if (random_id != id_)
150 res = findSuccessor(random_id);
151 XBT_DEBUG("The successor of node %d is %d", random_id, res);
154 /* Sets a finger of the current node.
156 * @param node the current node
157 * @param finger_index index of the finger to set (0 to nb_bits - 1)
158 * @param id the id to set for this finger
160 void Node::setFinger(int finger_index, int id)
162 if (id != fingers_[finger_index]) {
163 fingers_[finger_index] = id;
164 XBT_VERB("My new finger #%d is %d", finger_index, id);
168 /* Sets the predecessor of the current node.
169 * @param id the id to predecessor, or -1 to unset the predecessor
171 void Node::setPredecessor(int predecessor_id)
173 if (predecessor_id != pred_id_) {
174 pred_id_ = predecessor_id;
175 XBT_VERB("My new predecessor is %d", predecessor_id);
179 /** refreshes the finger table of the current node (called periodically) */
180 void Node::fixFingers()
182 XBT_DEBUG("Fixing fingers");
183 int id = findSuccessor(id_ + (1U << next_finger_to_fix));
185 if (id != fingers_[next_finger_to_fix]) {
186 setFinger(next_finger_to_fix, id);
189 next_finger_to_fix = (next_finger_to_fix + 1) % nb_bits;
193 /** Displays the finger table of a node. */
194 void Node::printFingerTable()
196 if (XBT_LOG_ISENABLED(s4u_chord, xbt_log_priority_verbose)) {
197 XBT_VERB("My finger table:");
198 XBT_VERB("Start | Succ");
199 for (int i = 0; i < nb_bits; i++) {
200 XBT_VERB(" %3u | %3d", (id_ + (1U << i)) % nb_keys, fingers_[i]);
203 XBT_VERB("Predecessor: %d", pred_id_);
207 /* checks whether the predecessor has failed (called periodically) */
208 void Node::checkPredecessor()
210 XBT_DEBUG("Checking whether my predecessor is alive");
211 void* data = nullptr;
215 simgrid::s4u::MailboxPtr mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(pred_id_));
216 simgrid::s4u::MailboxPtr return_mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(id_) + "_is_alive");
218 ChordMessage* message = new ChordMessage(PREDECESSOR_ALIVE);
219 message->request_id = pred_id_;
220 message->answer_to = return_mailbox;
222 XBT_DEBUG("Sending a 'Predecessor Alive' request to my predecessor %d", pred_id_);
224 mailbox->put(message, 10, timeout);
225 } catch (simgrid::TimeoutError& e) {
226 XBT_DEBUG("Failed to send the 'Predecessor Alive' request to %d", pred_id_);
231 // receive the answer
232 XBT_DEBUG("Sent 'Predecessor Alive' request to %d, waiting for the answer on my mailbox '%s'", pred_id_,
233 message->answer_to->get_cname());
234 simgrid::s4u::CommPtr comm = return_mailbox->get_async(&data);
237 comm->wait_for(timeout);
238 XBT_DEBUG("Received the answer to my 'Predecessor Alive': my predecessor %d is alive", pred_id_);
239 delete static_cast<ChordMessage*>(data);
240 } catch (simgrid::TimeoutError& e) {
241 XBT_DEBUG("Failed to receive the answer to my 'Predecessor Alive' request");
246 /* Asks its predecessor to a remote node
248 * @param ask_to the node to ask to
249 * @return the id of its predecessor node, or -1 if the request failed (or if the node does not know its predecessor)
251 int Node::remoteGetPredecessor(int ask_to)
253 int predecessor_id = -1;
254 void* data = nullptr;
255 simgrid::s4u::MailboxPtr mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(ask_to));
256 simgrid::s4u::MailboxPtr return_mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(id_) + "_pred");
258 ChordMessage* message = new ChordMessage(GET_PREDECESSOR);
259 message->request_id = id_;
260 message->answer_to = return_mailbox;
262 // send a "Get Predecessor" request to ask_to_id
263 XBT_DEBUG("Sending a 'Get Predecessor' request to %d", ask_to);
265 mailbox->put(message, 10, timeout);
266 } catch (simgrid::TimeoutError& e) {
267 XBT_DEBUG("Failed to send the 'Get Predecessor' request to %d", ask_to);
269 return predecessor_id;
272 // receive the answer
273 XBT_DEBUG("Sent 'Get Predecessor' request to %d, waiting for the answer on my mailbox '%s'", ask_to,
274 message->answer_to->get_cname());
275 simgrid::s4u::CommPtr comm = return_mailbox->get_async(&data);
278 comm->wait_for(timeout);
279 ChordMessage* answer = static_cast<ChordMessage*>(data);
280 XBT_DEBUG("Received the answer to my 'Get Predecessor' request: the predecessor of node %d is %d", ask_to,
282 predecessor_id = answer->answer_id;
284 } catch (simgrid::TimeoutError& e) {
285 XBT_DEBUG("Failed to receive the answer to my 'Get Predecessor' request");
286 delete static_cast<ChordMessage*>(data);
289 return predecessor_id;
292 /* Returns the closest preceding finger of an id with respect to the finger table of the current node.
294 * @param id the id to find
295 * @return the closest preceding finger of that id
297 int Node::closestPrecedingFinger(int id)
299 for (int i = nb_bits - 1; i >= 0; i--) {
300 if (is_in_interval(fingers_[i], id_ + 1, id - 1)) {
307 /* Makes the current node find the successor node of an id.
309 * @param id the id to find
310 * @return the id of the successor node, or -1 if the request failed
312 int Node::findSuccessor(int id)
314 // is my successor the successor?
315 if (is_in_interval(id, id_ + 1, fingers_[0])) {
319 // otherwise, ask the closest preceding finger in my table
320 return remoteFindSuccessor(closestPrecedingFinger(id), id);
323 int Node::remoteFindSuccessor(int ask_to, int id)
326 void* data = nullptr;
327 simgrid::s4u::MailboxPtr mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(ask_to));
328 simgrid::s4u::MailboxPtr return_mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(id_) + "_succ");
330 ChordMessage* message = new ChordMessage(FIND_SUCCESSOR);
331 message->request_id = id_;
332 message->answer_to = return_mailbox;
334 // send a "Find Successor" request to ask_to_id
335 XBT_DEBUG("Sending a 'Find Successor' request to %d for id %d", ask_to, id);
337 mailbox->put(message, 10, timeout);
338 } catch (simgrid::TimeoutError& e) {
339 XBT_DEBUG("Failed to send the 'Find Successor' request to %d for id %d", ask_to, id_);
343 // receive the answer
344 XBT_DEBUG("Sent a 'Find Successor' request to %d for key %d, waiting for the answer", ask_to, id);
345 simgrid::s4u::CommPtr comm = return_mailbox->get_async(&data);
348 comm->wait_for(timeout);
349 ChordMessage* answer = static_cast<ChordMessage*>(data);
350 XBT_DEBUG("Received the answer to my 'Find Successor' request for id %d: the successor of key %d is %d",
351 answer->request_id, id_, answer->answer_id);
352 successor = answer->answer_id;
354 } catch (simgrid::TimeoutError& e) {
355 XBT_DEBUG("Failed to receive the answer to my 'Find Successor' request");
356 delete static_cast<ChordMessage*>(data);
362 /* Notifies the current node that its predecessor may have changed. */
363 void Node::notify(int predecessor_candidate_id)
365 if (pred_id_ == -1 || is_in_interval(predecessor_candidate_id, pred_id_ + 1, id_ - 1)) {
366 setPredecessor(predecessor_candidate_id);
369 XBT_DEBUG("I don't have to change my predecessor to %d", predecessor_candidate_id);
373 /* Notifies a remote node that its predecessor may have changed. */
374 void Node::remoteNotify(int notify_id, int predecessor_candidate_id)
376 ChordMessage* message = new ChordMessage(NOTIFY);
377 message->request_id = predecessor_candidate_id;
378 message->answer_to = nullptr;
380 // send a "Notify" request to notify_id
381 XBT_DEBUG("Sending a 'Notify' request to %d", notify_id);
382 simgrid::s4u::MailboxPtr mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(notify_id));
383 mailbox->put_init(message, 10)->detach(ChordMessage::destroy);
386 /* This function is called periodically. It checks the immediate successor of the current node. */
387 void Node::stabilize()
389 XBT_DEBUG("Stabilizing node");
391 // get the predecessor of my immediate successor
392 int candidate_id = pred_id_;
393 int successor_id = fingers_[0];
394 if (successor_id != id_)
395 candidate_id = remoteGetPredecessor(successor_id);
397 // this node is a candidate to become my new successor
398 if (candidate_id != -1 && is_in_interval(candidate_id, id_ + 1, successor_id - 1)) {
399 setFinger(0, candidate_id);
401 if (successor_id != id_) {
402 remoteNotify(successor_id, id_);
406 /* This function is called when a node receives a message.
408 * @param message the message to handle (don't touch it afterward: it will be destroyed, reused or forwarded)
410 void Node::handleMessage(ChordMessage* message)
412 switch (message->type) {
414 XBT_DEBUG("Received a 'Find Successor' request from %s for id %d", message->issuer_host_name.c_str(),
415 message->request_id);
416 // is my successor the successor?
417 if (is_in_interval(message->request_id, id_ + 1, fingers_[0])) {
418 message->type = FIND_SUCCESSOR_ANSWER;
419 message->answer_id = fingers_[0];
420 XBT_DEBUG("Sending back a 'Find Successor Answer' to %s (mailbox %s): the successor of %d is %d",
421 message->issuer_host_name.c_str(), message->answer_to->get_cname(), message->request_id,
423 message->answer_to->put_init(message, 10)->detach(ChordMessage::destroy);
425 // otherwise, forward the request to the closest preceding finger in my table
426 int closest = closestPrecedingFinger(message->request_id);
427 XBT_DEBUG("Forwarding the 'Find Successor' request for id %d to my closest preceding finger %d",
428 message->request_id, closest);
429 simgrid::s4u::MailboxPtr mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(closest));
430 mailbox->put_init(message, 10)->detach(ChordMessage::destroy);
434 case GET_PREDECESSOR:
435 XBT_DEBUG("Receiving a 'Get Predecessor' request from %s", message->issuer_host_name.c_str());
436 message->type = GET_PREDECESSOR_ANSWER;
437 message->answer_id = pred_id_;
438 XBT_DEBUG("Sending back a 'Get Predecessor Answer' to %s via mailbox '%s': my predecessor is %d",
439 message->issuer_host_name.c_str(), message->answer_to->get_cname(), message->answer_id);
440 message->answer_to->put_init(message, 10)->detach(ChordMessage::destroy);
444 // someone is telling me that he may be my new predecessor
445 XBT_DEBUG("Receiving a 'Notify' request from %s", message->issuer_host_name.c_str());
446 notify(message->request_id);
450 case PREDECESSOR_LEAVING:
451 // my predecessor is about to quit
452 XBT_DEBUG("Receiving a 'Predecessor Leaving' message from %s", message->issuer_host_name.c_str());
453 // modify my predecessor
454 setPredecessor(message->request_id);
457 >> notify my new predecessor
458 >> send a notify_predecessors !!
462 case SUCCESSOR_LEAVING:
463 // my successor is about to quit
464 XBT_DEBUG("Receiving a 'Successor Leaving' message from %s", message->issuer_host_name.c_str());
465 // modify my successor FIXME : this should be implicit ?
466 setFinger(0, message->request_id);
469 >> notify my new successor
470 >> update my table & predecessors table */
473 case PREDECESSOR_ALIVE:
474 XBT_DEBUG("Receiving a 'Predecessor Alive' request from %s", message->issuer_host_name.c_str());
475 message->type = PREDECESSOR_ALIVE_ANSWER;
476 XBT_DEBUG("Sending back a 'Predecessor Alive Answer' to %s (mailbox %s)", message->issuer_host_name.c_str(),
477 message->answer_to->get_cname());
478 message->answer_to->put_init(message, 10)->detach(ChordMessage::destroy);
482 XBT_DEBUG("Ignoring unexpected message: %d from %s", message->type, message->issuer_host_name.c_str());