1 /* Copyright (c) 2010-2017. 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 /* Initializes the current node as the first one of the system */
44 Node::Node(std::vector<std::string> args)
46 xbt_assert(args.size() == 3 || args.size() == 5, "Wrong number of arguments for this node");
49 id_ = std::stoi(args[1]);
50 stream = simgrid::s4u::this_actor::getHost()->extension<HostChord>()->getStream();
51 mailbox_ = simgrid::s4u::Mailbox::byName(std::to_string(id_));
52 next_finger_to_fix = 0;
53 fingers_ = new int[nb_bits];
55 for (int i = 0; i < nb_bits; i++) {
59 if (args.size() == 3) { // first ring
60 deadline_ = std::stod(args[2]);
61 start_time_ = simgrid::s4u::Engine::getClock();
62 XBT_DEBUG("Create a new Chord ring...");
64 known_id_ = std::stoi(args[2]);
65 start_time_ = std::stod(args[3]);
66 deadline_ = std::stod(args[4]);
67 XBT_DEBUG("Hey! Let's join the system in %f seconds (shall leave at time %f)", start_time_,
68 start_time_ + deadline_);
76 /* Makes the current node join the ring, knowing the id of a node already in the ring
78 * \param known_id id of a node already in the ring
79 * \return true if the join operation succeeded
82 void Node::join(int known_id)
84 XBT_INFO("Joining the ring with id %d, knowing node %d", id_, known_id);
85 setPredecessor(-1); // no predecessor (yet)
87 int successor_id = remoteFindSuccessor(known_id, id_);
88 if (successor_id == -1) {
89 XBT_INFO("Cannot join the ring.");
91 setFinger(0, successor_id);
97 /* Makes the current node quit the system */
100 XBT_INFO("Well Guys! I Think it's time for me to leave ;)");
105 /* Notifies the successor and the predecessor of the current node before leaving */
106 void Node::notifyAndQuit()
108 // send the PREDECESSOR_LEAVING to our successor
109 ChordMessage* pred_msg = new ChordMessage(PREDECESSOR_LEAVING);
110 pred_msg->request_id = pred_id_;
111 pred_msg->answer_to = mailbox_;
113 XBT_DEBUG("Sending a 'PREDECESSOR_LEAVING' to my successor %d", fingers_[0]);
115 simgrid::s4u::Mailbox::byName(std::to_string(fingers_[0]))->put(pred_msg, 10, timeout);
116 } catch (xbt_ex& e) {
117 if (e.category == timeout_error) {
118 XBT_DEBUG("Timeout expired when sending a 'PREDECESSOR_LEAVING' to my successor %d", fingers_[0]);
123 if (pred_id_ != -1 && pred_id_ != id_) {
124 // send the SUCCESSOR_LEAVING to our predecessor (only if I have one that is not me)
125 ChordMessage* succ_msg = new ChordMessage(SUCCESSOR_LEAVING);
126 succ_msg->request_id = fingers_[0];
127 succ_msg->answer_to = mailbox_;
128 XBT_DEBUG("Sending a 'SUCCESSOR_LEAVING' to my predecessor %d", pred_id_);
131 simgrid::s4u::Mailbox::byName(std::to_string(pred_id_))->put(succ_msg, 10, timeout);
132 } catch (xbt_ex& e) {
133 if (e.category == timeout_error) {
134 XBT_DEBUG("Timeout expired when sending a 'SUCCESSOR_LEAVING' to my predecessor %d", pred_id_);
141 /* Performs a find successor request to a random id */
142 void Node::randomLookup()
145 int random_index = RngStream_RandInt(stream, 0, nb_bits - 1);
146 int random_id = fingers_[random_index];
147 XBT_DEBUG("Making a lookup request for id %d", random_id);
148 if (random_id != id_)
149 res = findSuccessor(random_id);
150 XBT_DEBUG("The successor of node %d is %d", random_id, res);
153 /* Sets a finger of the current node.
155 * \param node the current node
156 * \param finger_index index of the finger to set (0 to nb_bits - 1)
157 * \param id the id to set for this finger
159 void Node::setFinger(int finger_index, int id)
161 if (id != fingers_[finger_index]) {
162 fingers_[finger_index] = id;
163 XBT_VERB("My new finger #%d is %d", finger_index, id);
167 /* Sets the predecessor of the current node.
168 * \param id the id to predecessor, or -1 to unset the predecessor
170 void Node::setPredecessor(int predecessor_id)
172 if (predecessor_id != pred_id_) {
173 pred_id_ = predecessor_id;
174 XBT_VERB("My new predecessor is %d", predecessor_id);
178 /** refreshes the finger table of the current node (called periodically) */
179 void Node::fixFingers()
181 XBT_DEBUG("Fixing fingers");
182 int id = findSuccessor(id_ + powers2[next_finger_to_fix]);
184 if (id != fingers_[next_finger_to_fix]) {
185 setFinger(next_finger_to_fix, id);
188 next_finger_to_fix = (next_finger_to_fix + 1) % nb_bits;
192 /** Displays the finger table of a node. */
193 void Node::printFingerTable()
195 if (XBT_LOG_ISENABLED(s4u_chord, xbt_log_priority_verbose)) {
196 XBT_VERB("My finger table:");
197 XBT_VERB("Start | Succ");
198 for (int i = 0; i < nb_bits; i++) {
199 XBT_VERB(" %3d | %3d", (id_ + powers2[i]) % nb_keys, fingers_[i]);
202 XBT_VERB("Predecessor: %d", pred_id_);
206 /* checks whether the predecessor has failed (called periodically) */
207 void Node::checkPredecessor()
209 XBT_DEBUG("Checking whether my predecessor is alive");
210 void* data = nullptr;
214 simgrid::s4u::MailboxPtr mailbox = simgrid::s4u::Mailbox::byName(std::to_string(pred_id_));
215 simgrid::s4u::MailboxPtr return_mailbox = simgrid::s4u::Mailbox::byName(std::to_string(id_) + "_is_alive");
217 ChordMessage* message = new ChordMessage(PREDECESSOR_ALIVE);
218 message->request_id = pred_id_;
219 message->answer_to = return_mailbox;
221 XBT_DEBUG("Sending a 'Predecessor Alive' request to my predecessor %d", pred_id_);
223 mailbox->put(message, 10, timeout);
224 } catch (xbt_ex& e) {
225 if (e.category == timeout_error) {
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->getName());
234 simgrid::s4u::CommPtr comm = return_mailbox->get_async(&data);
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 (xbt_ex& e) {
241 if (e.category == timeout_error) {
242 XBT_DEBUG("Failed to receive the answer to my 'Predecessor Alive' request");
248 /* Asks its predecessor to a remote node
250 * \param ask_to the node to ask to
251 * \return the id of its predecessor node, or -1 if the request failed (or if the node does not know its predecessor)
253 int Node::remoteGetPredecessor(int ask_to)
255 int predecessor_id = -1;
256 void* data = nullptr;
257 simgrid::s4u::MailboxPtr mailbox = simgrid::s4u::Mailbox::byName(std::to_string(ask_to));
258 simgrid::s4u::MailboxPtr return_mailbox = simgrid::s4u::Mailbox::byName(std::to_string(id_) + "_pred");
260 ChordMessage* message = new ChordMessage(GET_PREDECESSOR);
261 message->request_id = id_;
262 message->answer_to = return_mailbox;
264 // send a "Get Predecessor" request to ask_to_id
265 XBT_DEBUG("Sending a 'Get Predecessor' request to %d", ask_to);
267 mailbox->put(message, 10, timeout);
268 } catch (xbt_ex& e) {
269 if (e.category == timeout_error) {
270 XBT_DEBUG("Failed to send the 'Get Predecessor' request to %d", ask_to);
272 return predecessor_id;
276 // receive the answer
277 XBT_DEBUG("Sent 'Get Predecessor' request to %d, waiting for the answer on my mailbox '%s'", ask_to,
278 message->answer_to->getName());
279 simgrid::s4u::CommPtr comm = return_mailbox->get_async(&data);
283 ChordMessage* answer = static_cast<ChordMessage*>(data);
284 XBT_DEBUG("Received the answer to my 'Get Predecessor' request: the predecessor of node %d is %d", ask_to,
286 predecessor_id = answer->answer_id;
288 } catch (xbt_ex& e) {
289 if (e.category == timeout_error) {
290 XBT_DEBUG("Failed to receive the answer to my 'Get Predecessor' request");
291 delete static_cast<ChordMessage*>(data);
295 return predecessor_id;
298 /* Returns the closest preceding finger of an id with respect to the finger table of the current node.
300 * \param id the id to find
301 * \return the closest preceding finger of that id
303 int Node::closestPrecedingFinger(int id)
305 for (int i = nb_bits - 1; i >= 0; i--) {
306 if (is_in_interval(fingers_[i], id_ + 1, id - 1)) {
313 /* Makes the current node find the successor node of an id.
315 * \param id the id to find
316 * \return the id of the successor node, or -1 if the request failed
318 int Node::findSuccessor(int id)
320 // is my successor the successor?
321 if (is_in_interval(id, id_ + 1, fingers_[0])) {
325 // otherwise, ask the closest preceding finger in my table
326 return remoteFindSuccessor(closestPrecedingFinger(id), id);
329 int Node::remoteFindSuccessor(int ask_to, int id)
332 void* data = nullptr;
333 simgrid::s4u::MailboxPtr mailbox = simgrid::s4u::Mailbox::byName(std::to_string(ask_to));
334 simgrid::s4u::MailboxPtr return_mailbox = simgrid::s4u::Mailbox::byName(std::to_string(id_) + "_succ");
336 ChordMessage* message = new ChordMessage(FIND_SUCCESSOR);
337 message->request_id = id_;
338 message->answer_to = return_mailbox;
340 // send a "Find Successor" request to ask_to_id
341 XBT_DEBUG("Sending a 'Find Successor' request to %d for id %d", ask_to, id);
343 mailbox->put(message, 10, timeout);
344 } catch (xbt_ex& e) {
345 if (e.category == timeout_error) {
346 XBT_DEBUG("Failed to send the 'Find Successor' request to %d for id %d", ask_to, id_);
351 // receive the answer
352 XBT_DEBUG("Sent a 'Find Successor' request to %d for key %d, waiting for the answer", ask_to, id);
353 simgrid::s4u::CommPtr comm = return_mailbox->get_async(&data);
357 ChordMessage* answer = static_cast<ChordMessage*>(data);
358 XBT_DEBUG("Received the answer to my 'Find Successor' request for id %d: the successor of key %d is %d",
359 answer->request_id, id_, answer->answer_id);
360 successor = answer->answer_id;
362 } catch (xbt_ex& e) {
363 if (e.category == timeout_error) {
364 XBT_DEBUG("Failed to receive the answer to my 'Find Successor' request");
365 delete static_cast<ChordMessage*>(data);
371 /* Notifies the current node that its predecessor may have changed. */
372 void Node::notify(int predecessor_candidate_id)
374 if (pred_id_ == -1 || is_in_interval(predecessor_candidate_id, pred_id_ + 1, id_ - 1)) {
375 setPredecessor(predecessor_candidate_id);
378 XBT_DEBUG("I don't have to change my predecessor to %d", predecessor_candidate_id);
382 /* Notifies a remote node that its predecessor may have changed. */
383 void Node::remoteNotify(int notify_id, int predecessor_candidate_id)
385 ChordMessage* message = new ChordMessage(NOTIFY);
386 message->request_id = predecessor_candidate_id;
387 message->answer_to = nullptr;
389 // send a "Notify" request to notify_id
390 XBT_DEBUG("Sending a 'Notify' request to %d", notify_id);
391 simgrid::s4u::MailboxPtr mailbox = simgrid::s4u::Mailbox::byName(std::to_string(notify_id));
392 mailbox->put_init(message, 10)->detach();
395 /* This function is called periodically. It checks the immediate successor of the current node. */
396 void Node::stabilize()
398 XBT_DEBUG("Stabilizing node");
400 // get the predecessor of my immediate successor
401 int candidate_id = pred_id_;
402 int successor_id = fingers_[0];
403 if (successor_id != id_)
404 candidate_id = remoteGetPredecessor(successor_id);
406 // this node is a candidate to become my new successor
407 if (candidate_id != -1 && is_in_interval(candidate_id, id_ + 1, successor_id - 1)) {
408 setFinger(0, candidate_id);
410 if (successor_id != id_) {
411 remoteNotify(successor_id, id_);
415 /* This function is called when a node receives a message.
417 * \param message the message to handle (don't touch it afterward: it will be destroyed, reused or forwarded)
419 void Node::handleMessage(ChordMessage* message)
421 switch (message->type) {
423 XBT_DEBUG("Received a 'Find Successor' request from %s for id %d", message->issuer_host_name.c_str(),
424 message->request_id);
425 // is my successor the successor?
426 if (is_in_interval(message->request_id, id_ + 1, fingers_[0])) {
427 message->type = FIND_SUCCESSOR_ANSWER;
428 message->answer_id = fingers_[0];
429 XBT_DEBUG("Sending back a 'Find Successor Answer' to %s (mailbox %s): the successor of %d is %d",
430 message->issuer_host_name.c_str(), message->answer_to->getName(), message->request_id,
432 message->answer_to->put_init(message, 10)->detach();
434 // otherwise, forward the request to the closest preceding finger in my table
435 int closest = closestPrecedingFinger(message->request_id);
436 XBT_DEBUG("Forwarding the 'Find Successor' request for id %d to my closest preceding finger %d",
437 message->request_id, closest);
438 simgrid::s4u::MailboxPtr mailbox = simgrid::s4u::Mailbox::byName(std::to_string(closest));
439 mailbox->put_init(message, 10)->detach();
443 case GET_PREDECESSOR:
444 XBT_DEBUG("Receiving a 'Get Predecessor' request from %s", message->issuer_host_name.c_str());
445 message->type = GET_PREDECESSOR_ANSWER;
446 message->answer_id = pred_id_;
447 XBT_DEBUG("Sending back a 'Get Predecessor Answer' to %s via mailbox '%s': my predecessor is %d",
448 message->issuer_host_name.c_str(), message->answer_to->getName(), message->answer_id);
449 message->answer_to->put_init(message, 10)->detach();
453 // someone is telling me that he may be my new predecessor
454 XBT_DEBUG("Receiving a 'Notify' request from %s", message->issuer_host_name.c_str());
455 notify(message->request_id);
459 case PREDECESSOR_LEAVING:
460 // my predecessor is about to quit
461 XBT_DEBUG("Receiving a 'Predecessor Leaving' message from %s", message->issuer_host_name.c_str());
462 // modify my predecessor
463 setPredecessor(message->request_id);
466 >> notify my new predecessor
467 >> send a notify_predecessors !!
471 case SUCCESSOR_LEAVING:
472 // my successor is about to quit
473 XBT_DEBUG("Receiving a 'Successor Leaving' message from %s", message->issuer_host_name.c_str());
474 // modify my successor FIXME : this should be implicit ?
475 setFinger(0, message->request_id);
478 >> notify my new successor
479 >> update my table & predecessors table */
482 case PREDECESSOR_ALIVE:
483 XBT_DEBUG("Receiving a 'Predecessor Alive' request from %s", message->issuer_host_name.c_str());
484 message->type = PREDECESSOR_ALIVE_ANSWER;
485 XBT_DEBUG("Sending back a 'Predecessor Alive Answer' to %s (mailbox %s)", message->issuer_host_name.c_str(),
486 message->answer_to->getName());
487 message->answer_to->put_init(message, 10)->detach();
491 XBT_DEBUG("Ignoring unexpected message: %d from %s", message->type, message->issuer_host_name.c_str());