1 /* Copyright (c) 2010-2019. 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_.resize(nb_bits, id_);
60 if (args.size() == 3) { // first ring
61 deadline_ = std::stod(args[2]);
62 start_time_ = simgrid::s4u::Engine::get_clock();
63 XBT_DEBUG("Create a new Chord ring...");
65 known_id_ = std::stoi(args[2]);
66 start_time_ = std::stod(args[3]);
67 deadline_ = std::stod(args[4]);
68 XBT_DEBUG("Hey! Let's join the system in %f seconds (shall leave at time %f)", start_time_,
69 start_time_ + deadline_);
73 /* Makes the current node join the ring, knowing the id of a node already in the ring
75 * @param known_id id of a node already in the ring
76 * @return true if the join operation succeeded
79 void Node::join(int known_id)
81 XBT_INFO("Joining the ring with id %d, knowing node %d", id_, known_id);
82 setPredecessor(-1); // no predecessor (yet)
84 int successor_id = remoteFindSuccessor(known_id, id_);
85 if (successor_id == -1) {
86 XBT_INFO("Cannot join the ring.");
88 setFinger(0, successor_id);
94 /* Makes the current node quit the system */
97 XBT_INFO("Well Guys! I Think it's time for me to leave ;)");
102 /* Notifies the successor and the predecessor of the current node before leaving */
103 void Node::notifyAndQuit()
105 // send the PREDECESSOR_LEAVING to our successor
106 ChordMessage* pred_msg = new ChordMessage(PREDECESSOR_LEAVING);
107 pred_msg->request_id = pred_id_;
108 pred_msg->answer_to = mailbox_;
110 XBT_DEBUG("Sending a 'PREDECESSOR_LEAVING' to my successor %d", fingers_[0]);
112 simgrid::s4u::Mailbox::by_name(std::to_string(fingers_[0]))->put(pred_msg, 10, timeout);
113 } catch (const simgrid::TimeoutException&) {
114 XBT_DEBUG("Timeout expired when sending a 'PREDECESSOR_LEAVING' to my successor %d", fingers_[0]);
118 if (pred_id_ != -1 && pred_id_ != id_) {
119 // send the SUCCESSOR_LEAVING to our predecessor (only if I have one that is not me)
120 ChordMessage* succ_msg = new ChordMessage(SUCCESSOR_LEAVING);
121 succ_msg->request_id = fingers_[0];
122 succ_msg->answer_to = mailbox_;
123 XBT_DEBUG("Sending a 'SUCCESSOR_LEAVING' to my predecessor %d", pred_id_);
126 simgrid::s4u::Mailbox::by_name(std::to_string(pred_id_))->put(succ_msg, 10, timeout);
127 } catch (const simgrid::TimeoutException&) {
128 XBT_DEBUG("Timeout expired when sending a 'SUCCESSOR_LEAVING' to my predecessor %d", pred_id_);
134 /* Performs a find successor request to a random id */
135 void Node::randomLookup()
138 int random_index = RngStream_RandInt(stream, 0, nb_bits - 1);
139 int random_id = fingers_[random_index];
140 XBT_DEBUG("Making a lookup request for id %d", random_id);
141 if (random_id != id_)
142 res = findSuccessor(random_id);
143 XBT_DEBUG("The successor of node %d is %d", random_id, res);
146 /* Sets a finger of the current node.
148 * @param node the current node
149 * @param finger_index index of the finger to set (0 to nb_bits - 1)
150 * @param id the id to set for this finger
152 void Node::setFinger(int finger_index, int id)
154 if (id != fingers_[finger_index]) {
155 fingers_[finger_index] = id;
156 XBT_VERB("My new finger #%d is %d", finger_index, id);
160 /* Sets the predecessor of the current node.
161 * @param id the id to predecessor, or -1 to unset the predecessor
163 void Node::setPredecessor(int predecessor_id)
165 if (predecessor_id != pred_id_) {
166 pred_id_ = predecessor_id;
167 XBT_VERB("My new predecessor is %d", predecessor_id);
171 /** refreshes the finger table of the current node (called periodically) */
172 void Node::fixFingers()
174 XBT_DEBUG("Fixing fingers");
175 int id = findSuccessor(id_ + (1U << next_finger_to_fix));
177 if (id != fingers_[next_finger_to_fix]) {
178 setFinger(next_finger_to_fix, id);
181 next_finger_to_fix = (next_finger_to_fix + 1) % nb_bits;
185 /** Displays the finger table of a node. */
186 void Node::printFingerTable()
188 if (XBT_LOG_ISENABLED(s4u_chord, xbt_log_priority_verbose)) {
189 XBT_VERB("My finger table:");
190 XBT_VERB("Start | Succ");
191 for (int i = 0; i < nb_bits; i++) {
192 XBT_VERB(" %3u | %3d", (id_ + (1U << i)) % nb_keys, fingers_[i]);
195 XBT_VERB("Predecessor: %d", pred_id_);
199 /* checks whether the predecessor has failed (called periodically) */
200 void Node::checkPredecessor()
202 XBT_DEBUG("Checking whether my predecessor is alive");
203 void* data = nullptr;
207 simgrid::s4u::Mailbox* mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(pred_id_));
208 simgrid::s4u::Mailbox* return_mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(id_) + "_is_alive");
210 ChordMessage* message = new ChordMessage(PREDECESSOR_ALIVE);
211 message->request_id = pred_id_;
212 message->answer_to = return_mailbox;
214 XBT_DEBUG("Sending a 'Predecessor Alive' request to my predecessor %d", pred_id_);
216 mailbox->put(message, 10, timeout);
217 } catch (const simgrid::TimeoutException&) {
218 XBT_DEBUG("Failed to send the 'Predecessor Alive' request to %d", pred_id_);
223 // receive the answer
224 XBT_DEBUG("Sent 'Predecessor Alive' request to %d, waiting for the answer on my mailbox '%s'", pred_id_,
225 message->answer_to->get_cname());
226 simgrid::s4u::CommPtr comm = return_mailbox->get_async(&data);
229 comm->wait_for(timeout);
230 XBT_DEBUG("Received the answer to my 'Predecessor Alive': my predecessor %d is alive", pred_id_);
231 delete static_cast<ChordMessage*>(data);
232 } catch (const simgrid::TimeoutException&) {
233 XBT_DEBUG("Failed to receive the answer to my 'Predecessor Alive' request");
238 /* Asks its predecessor to a remote node
240 * @param ask_to the node to ask to
241 * @return the id of its predecessor node, or -1 if the request failed (or if the node does not know its predecessor)
243 int Node::remoteGetPredecessor(int ask_to)
245 int predecessor_id = -1;
246 void* data = nullptr;
247 simgrid::s4u::Mailbox* mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(ask_to));
248 simgrid::s4u::Mailbox* return_mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(id_) + "_pred");
250 ChordMessage* message = new ChordMessage(GET_PREDECESSOR);
251 message->request_id = id_;
252 message->answer_to = return_mailbox;
254 // send a "Get Predecessor" request to ask_to_id
255 XBT_DEBUG("Sending a 'Get Predecessor' request to %d", ask_to);
257 mailbox->put(message, 10, timeout);
258 } catch (const simgrid::TimeoutException&) {
259 XBT_DEBUG("Failed to send the 'Get Predecessor' request to %d", ask_to);
261 return predecessor_id;
264 // receive the answer
265 XBT_DEBUG("Sent 'Get Predecessor' request to %d, waiting for the answer on my mailbox '%s'", ask_to,
266 message->answer_to->get_cname());
267 simgrid::s4u::CommPtr comm = return_mailbox->get_async(&data);
270 comm->wait_for(timeout);
271 ChordMessage* answer = static_cast<ChordMessage*>(data);
272 XBT_DEBUG("Received the answer to my 'Get Predecessor' request: the predecessor of node %d is %d", ask_to,
274 predecessor_id = answer->answer_id;
276 } catch (const simgrid::TimeoutException&) {
277 XBT_DEBUG("Failed to receive the answer to my 'Get Predecessor' request");
278 delete static_cast<ChordMessage*>(data);
281 return predecessor_id;
284 /* Returns the closest preceding finger of an id with respect to the finger table of the current node.
286 * @param id the id to find
287 * @return the closest preceding finger of that id
289 int Node::closestPrecedingFinger(int id)
291 for (int i = nb_bits - 1; i >= 0; i--) {
292 if (is_in_interval(fingers_[i], id_ + 1, id - 1)) {
299 /* Makes the current node find the successor node of an id.
301 * @param id the id to find
302 * @return the id of the successor node, or -1 if the request failed
304 int Node::findSuccessor(int id)
306 // is my successor the successor?
307 if (is_in_interval(id, id_ + 1, fingers_[0])) {
311 // otherwise, ask the closest preceding finger in my table
312 return remoteFindSuccessor(closestPrecedingFinger(id), id);
315 int Node::remoteFindSuccessor(int ask_to, int id)
318 void* data = nullptr;
319 simgrid::s4u::Mailbox* mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(ask_to));
320 simgrid::s4u::Mailbox* return_mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(id_) + "_succ");
322 ChordMessage* message = new ChordMessage(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 simgrid::s4u::CommPtr comm = return_mailbox->get_async(&data);
340 comm->wait_for(timeout);
341 ChordMessage* answer = static_cast<ChordMessage*>(data);
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");
348 delete static_cast<ChordMessage*>(data);
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)
368 ChordMessage* message = new ChordMessage(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 simgrid::s4u::Mailbox* mailbox = simgrid::s4u::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) {
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 = 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 simgrid::s4u::Mailbox* mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(closest));
422 mailbox->put_init(message, 10)->detach(ChordMessage::destroy);
426 case GET_PREDECESSOR:
427 XBT_DEBUG("Receiving a 'Get Predecessor' request from %s", message->issuer_host_name.c_str());
428 message->type = 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);
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 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 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 PREDECESSOR_ALIVE:
466 XBT_DEBUG("Receiving a 'Predecessor Alive' request from %s", message->issuer_host_name.c_str());
467 message->type = 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", message->type, message->issuer_host_name.c_str());