2 /* Copyright (c) 2010-2013. The SimGrid Team.
3 * All rights reserved. */
5 /* This program is free software; you can redistribute it and/or modify it
6 * under the terms of the license (GNU LGPL) which comes with this package. */
11 #include "xbt/asserts.h"
12 #include "simgrid/modelchecker.h"
13 #include <xbt/RngStream.h>
15 /** @addtogroup MSG_examples
17 * - <b>chord/chord.c: Classical Chord P2P protocol</b>
18 * This example implements the well known Chord P2P protocol. Its
19 * main advantage is that it constitute a fully working non-trivial
20 * example. In addition, its implementation is rather efficient, as
21 * demonstrated in http://hal.inria.fr/inria-00602216/
25 XBT_LOG_NEW_DEFAULT_CATEGORY(msg_chord,
26 "Messages specific for this msg example");
30 #define MAILBOX_NAME_SIZE 10
32 static int nb_bits = 24;
33 static int nb_keys = 0;
34 static int timeout = 50;
35 static int max_simulation_time = 1000;
36 static int periodic_stabilize_delay = 20;
37 static int periodic_fix_fingers_delay = 120;
38 static int periodic_check_predecessor_delay = 120;
39 static int periodic_lookup_delay = 10;
41 extern long int smx_total_comms;
46 typedef struct s_finger {
48 char mailbox[MAILBOX_NAME_SIZE]; // string representation of the id
49 } s_finger_t, *finger_t;
54 typedef struct s_node {
56 char mailbox[MAILBOX_NAME_SIZE]; // my mailbox name (string representation of the id)
57 s_finger_t *fingers; // finger table, of size nb_bits (fingers[0] is my successor)
58 int pred_id; // predecessor id
59 char pred_mailbox[MAILBOX_NAME_SIZE]; // predecessor's mailbox name
60 int next_finger_to_fix; // index of the next finger to fix in fix_fingers()
61 msg_comm_t comm_receive; // current communication to receive
62 double last_change_date; // last time I changed a finger or my predecessor
63 RngStream stream; //RngStream for
67 * Types of tasks exchanged between nodes.
71 TASK_FIND_SUCCESSOR_ANSWER,
73 TASK_GET_PREDECESSOR_ANSWER,
75 TASK_SUCCESSOR_LEAVING,
76 TASK_PREDECESSOR_LEAVING,
77 TASK_PREDECESSOR_ALIVE,
78 TASK_PREDECESSOR_ALIVE_ANSWER
82 * Data attached with the tasks sent and received
84 typedef struct s_task_data {
85 e_task_type_t type; // type of task
86 int request_id; // id paramater (used by some types of tasks)
87 int request_finger; // finger parameter (used by some types of tasks)
88 int answer_id; // answer (used by some types of tasks)
89 char answer_to[MAILBOX_NAME_SIZE]; // mailbox to send an answer to (if any)
90 const char* issuer_host_name; // used for logging
91 } s_task_data_t, *task_data_t;
96 static void chord_initialize(void);
97 static void chord_exit(void);
98 static int normalize(int id);
99 static int is_in_interval(int id, int start, int end);
100 static void get_mailbox(int host_id, char* mailbox);
101 static void task_free(void* task);
102 static void print_finger_table(node_t node);
103 static void set_finger(node_t node, int finger_index, int id);
104 static void set_predecessor(node_t node, int predecessor_id);
107 static int node(int argc, char *argv[]);
108 static void handle_task(node_t node, msg_task_t task);
111 static void create(node_t node);
112 static int join(node_t node, int known_id);
113 static void leave(node_t node);
114 static int find_successor(node_t node, int id);
115 static int remote_find_successor(node_t node, int ask_to_id, int id);
116 static int remote_get_predecessor(node_t node, int ask_to_id);
117 static int closest_preceding_node(node_t node, int id);
118 static void stabilize(node_t node);
119 static void notify(node_t node, int predecessor_candidate_id);
120 static void remote_notify(node_t node, int notify_to, int predecessor_candidate_id);
121 static void fix_fingers(node_t node);
122 static void check_predecessor(node_t node);
123 static void random_lookup(node_t);
124 static void quit_notify(node_t node);
127 * \brief Global initialization of the Chord simulation.
129 static void chord_initialize(void)
131 // compute the powers of 2 once for all
132 powers2 = xbt_new(int, nb_bits);
135 for (i = 0; i < nb_bits; i++) {
140 XBT_DEBUG("Sets nb_keys to %d", nb_keys);
143 static void chord_exit(void)
149 * \brief Turns an id into an equivalent id in [0, nb_keys).
151 * \return the corresponding normalized id
153 static int normalize(int id)
155 // like id % nb_keys, but works with negatives numbers (and faster)
156 return id & (nb_keys - 1);
160 * \brief Returns whether an id belongs to the interval [start, end].
162 * The parameters are noramlized to make sure they are between 0 and nb_keys - 1).
163 * 1 belongs to [62, 3]
164 * 1 does not belong to [3, 62]
165 * 63 belongs to [62, 3]
166 * 63 does not belong to [3, 62]
167 * 24 belongs to [21, 29]
168 * 24 does not belong to [29, 21]
170 * \param id id to check
171 * \param start lower bound
172 * \param end upper bound
173 * \return a non-zero value if id in in [start, end]
175 static int is_in_interval(int id, int start, int end)
178 start = normalize(start);
179 end = normalize(end);
181 // make sure end >= start and id >= start
194 * \brief Gets the mailbox name of a host given its chord id.
195 * \param node_id id of a node
196 * \param mailbox pointer to where the mailbox name should be written
197 * (there must be enough space)
199 static void get_mailbox(int node_id, char* mailbox)
201 snprintf(mailbox, MAILBOX_NAME_SIZE - 1, "%d", node_id);
205 * \brief Frees the memory used by a task.
206 * \param task the MSG task to destroy
208 static void task_free(void* task)
210 // TODO add a parameter data_free_function to MSG_task_create?
212 xbt_free(MSG_task_get_data(task));
213 MSG_task_destroy(task);
218 * \brief Displays the finger table of a node.
221 static void print_finger_table(node_t node)
223 if (XBT_LOG_ISENABLED(msg_chord, xbt_log_priority_verbose)) {
225 XBT_VERB("My finger table:");
226 XBT_VERB("Start | Succ ");
227 for (i = 0; i < nb_bits; i++) {
228 XBT_VERB(" %3d | %3d ", (node->id + powers2[i]) % nb_keys, node->fingers[i].id);
230 XBT_VERB("Predecessor: %d", node->pred_id);
235 * \brief Sets a finger of the current node.
236 * \param node the current node
237 * \param finger_index index of the finger to set (0 to nb_bits - 1)
238 * \param id the id to set for this finger
240 static void set_finger(node_t node, int finger_index, int id)
242 if (id != node->fingers[finger_index].id) {
243 node->fingers[finger_index].id = id;
244 get_mailbox(id, node->fingers[finger_index].mailbox);
245 node->last_change_date = MSG_get_clock();
246 XBT_DEBUG("My new finger #%d is %d", finger_index, id);
251 * \brief Sets the predecessor of the current node.
252 * \param node the current node
253 * \param id the id to predecessor, or -1 to unset the predecessor
255 static void set_predecessor(node_t node, int predecessor_id)
257 if (predecessor_id != node->pred_id) {
258 node->pred_id = predecessor_id;
260 if (predecessor_id != -1) {
261 get_mailbox(predecessor_id, node->pred_mailbox);
263 node->last_change_date = MSG_get_clock();
265 XBT_DEBUG("My new predecessor is %d", predecessor_id);
270 * \brief Node Function
273 * - the id of a guy I know in the system (except for the first node)
274 * - the time to sleep before I join (except for the first node)
276 int node(int argc, char *argv[])
279 /* Reduce the run size for the MC */
281 periodic_stabilize_delay = 8;
282 periodic_fix_fingers_delay = 8;
283 periodic_check_predecessor_delay = 8;
286 double init_time = MSG_get_clock();
287 msg_task_t task_received = NULL;
289 int join_success = 0;
291 double next_stabilize_date = init_time + periodic_stabilize_delay;
292 double next_fix_fingers_date = init_time + periodic_fix_fingers_delay;
293 double next_check_predecessor_date = init_time + periodic_check_predecessor_delay;
294 double next_lookup_date = init_time + periodic_lookup_delay;
298 int sub_protocol = 0;
300 xbt_assert(argc == 3 || argc == 5, "Wrong number of arguments for this node");
302 // initialize my node
304 node.id = atoi(argv[1]);
305 get_mailbox(node.id, node.mailbox);
306 node.next_finger_to_fix = 0;
307 node.fingers = xbt_new0(s_finger_t, nb_bits);
308 node.last_change_date = init_time;
310 for (i = 0; i < nb_bits; i++) {
311 node.fingers[i].id = -1;
312 set_finger(&node, i, node.id);
315 if (argc == 3) { // first ring
316 deadline = atof(argv[2]);
321 int known_id = atoi(argv[2]);
322 //double sleep_time = atof(argv[3]);
323 deadline = atof(argv[4]);
326 // sleep before starting
327 XBT_DEBUG("Let's sleep during %f", sleep_time);
328 MSG_process_sleep(sleep_time);
330 XBT_DEBUG("Hey! Let's join the system.");
332 join_success = join(&node, known_id);
336 while (MSG_get_clock() < init_time + deadline
337 // && MSG_get_clock() < node.last_change_date + 1000
338 && MSG_get_clock() < max_simulation_time) {
340 if (node.comm_receive == NULL) {
341 task_received = NULL;
342 node.comm_receive = MSG_task_irecv(&task_received, node.mailbox);
343 // FIXME: do not make MSG_task_irecv() calls from several functions
346 //XBT_INFO("Node %d is ring member : %d", node.id, is_ring_member(known_id, node.id) != -1);
348 if (!MSG_comm_test(node.comm_receive)) {
350 // no task was received: make some periodic calls
353 if(!MC_visited_reduction() && no_op){
356 if(listen == 0 && (sub_protocol = MC_random(0, 4)) > 0){
357 if(sub_protocol == 1)
359 else if(sub_protocol == 2)
361 else if(sub_protocol == 3)
362 check_predecessor(&node);
364 random_lookup(&node);
367 MSG_process_sleep(5);
368 if(!MC_visited_reduction())
372 if (MSG_get_clock() >= next_stabilize_date) {
374 next_stabilize_date = MSG_get_clock() + periodic_stabilize_delay;
375 }else if (MSG_get_clock() >= next_fix_fingers_date) {
377 next_fix_fingers_date = MSG_get_clock() + periodic_fix_fingers_delay;
378 }else if (MSG_get_clock() >= next_check_predecessor_date) {
379 check_predecessor(&node);
380 next_check_predecessor_date = MSG_get_clock() + periodic_check_predecessor_delay;
381 }else if (MSG_get_clock() >= next_lookup_date) {
382 random_lookup(&node);
383 next_lookup_date = MSG_get_clock() + periodic_lookup_delay;
385 // nothing to do: sleep for a while
386 MSG_process_sleep(5);
391 // a transfer has occurred
393 msg_error_t status = MSG_comm_get_status(node.comm_receive);
395 if (status != MSG_OK) {
396 XBT_DEBUG("Failed to receive a task. Nevermind.");
397 MSG_comm_destroy(node.comm_receive);
398 node.comm_receive = NULL;
401 // the task was successfully received
402 MSG_comm_destroy(node.comm_receive);
403 node.comm_receive = NULL;
404 handle_task(&node, task_received);
409 if (node.comm_receive) {
410 /* handle last task if any */
411 if (MSG_comm_wait(node.comm_receive, 0) == MSG_OK)
412 task_free(task_received);
413 MSG_comm_destroy(node.comm_receive);
414 node.comm_receive = NULL;
421 // stop the simulation
422 xbt_free(node.fingers);
427 * \brief This function is called when the current node receives a task.
428 * \param node the current node
429 * \param task the task to handle (don't touch it then:
430 * it will be destroyed, reused or forwarded)
432 static void handle_task(node_t node, msg_task_t task) {
434 XBT_DEBUG("Handling task %p", task);
435 char mailbox[MAILBOX_NAME_SIZE];
436 task_data_t task_data = (task_data_t) MSG_task_get_data(task);
437 e_task_type_t type = task_data->type;
441 case TASK_FIND_SUCCESSOR:
442 XBT_DEBUG("Receiving a 'Find Successor' request from %s for id %d",
443 task_data->issuer_host_name, task_data->request_id);
444 // is my successor the successor?
445 if (is_in_interval(task_data->request_id, node->id + 1, node->fingers[0].id)) {
446 task_data->type = TASK_FIND_SUCCESSOR_ANSWER;
447 task_data->answer_id = node->fingers[0].id;
448 XBT_DEBUG("Sending back a 'Find Successor Answer' to %s (mailbox %s): the successor of %d is %d",
449 task_data->issuer_host_name,
450 task_data->answer_to,
451 task_data->request_id, task_data->answer_id);
452 MSG_task_dsend(task, task_data->answer_to, task_free);
455 // otherwise, forward the request to the closest preceding finger in my table
456 int closest = closest_preceding_node(node, task_data->request_id);
457 XBT_DEBUG("Forwarding the 'Find Successor' request for id %d to my closest preceding finger %d",
458 task_data->request_id, closest);
459 get_mailbox(closest, mailbox);
460 MSG_task_dsend(task, mailbox, task_free);
464 case TASK_GET_PREDECESSOR:
465 XBT_DEBUG("Receiving a 'Get Predecessor' request from %s", task_data->issuer_host_name);
466 task_data->type = TASK_GET_PREDECESSOR_ANSWER;
467 task_data->answer_id = node->pred_id;
468 XBT_DEBUG("Sending back a 'Get Predecessor Answer' to %s via mailbox '%s': my predecessor is %d",
469 task_data->issuer_host_name,
470 task_data->answer_to, task_data->answer_id);
471 MSG_task_dsend(task, task_data->answer_to, task_free);
475 // someone is telling me that he may be my new predecessor
476 XBT_DEBUG("Receiving a 'Notify' request from %s", task_data->issuer_host_name);
477 notify(node, task_data->request_id);
481 case TASK_PREDECESSOR_LEAVING:
482 // my predecessor is about to quit
483 XBT_DEBUG("Receiving a 'Predecessor Leaving' message from %s", task_data->issuer_host_name);
484 // modify my predecessor
485 set_predecessor(node, task_data->request_id);
488 >> notify my new predecessor
489 >> send a notify_predecessors !!
493 case TASK_SUCCESSOR_LEAVING:
494 // my successor is about to quit
495 XBT_DEBUG("Receiving a 'Successor Leaving' message from %s", task_data->issuer_host_name);
496 // modify my successor FIXME : this should be implicit ?
497 set_finger(node, 0, task_data->request_id);
500 >> notify my new successor
501 >> update my table & predecessors table */
504 case TASK_FIND_SUCCESSOR_ANSWER:
505 case TASK_GET_PREDECESSOR_ANSWER:
506 case TASK_PREDECESSOR_ALIVE_ANSWER:
507 XBT_DEBUG("Ignoring unexpected task of type %d (%p)", (int)type, task);
511 case TASK_PREDECESSOR_ALIVE:
512 XBT_DEBUG("Receiving a 'Predecessor Alive' request from %s", task_data->issuer_host_name);
513 task_data->type = TASK_PREDECESSOR_ALIVE_ANSWER;
514 XBT_DEBUG("Sending back a 'Predecessor Alive Answer' to %s (mailbox %s)",
515 task_data->issuer_host_name,
516 task_data->answer_to);
517 MSG_task_dsend(task, task_data->answer_to, task_free);
526 * \brief Initializes the current node as the first one of the system.
527 * \param node the current node
529 static void create(node_t node)
531 XBT_DEBUG("Create a new Chord ring...");
532 set_predecessor(node, -1); // -1 means that I have no predecessor
533 print_finger_table(node);
537 * \brief Makes the current node join the ring, knowing the id of a node
538 * already in the ring
539 * \param node the current node
540 * \param known_id id of a node already in the ring
541 * \return 1 if the join operation succeeded, 0 otherwise
543 static int join(node_t node, int known_id)
545 XBT_INFO("Joining the ring with id %d, knowing node %d", node->id, known_id);
546 set_predecessor(node, -1); // no predecessor (yet)
550 for (i = 0; i < nb_bits; i++) {
551 set_finger(node, i, known_id);
555 int successor_id = remote_find_successor(node, known_id, node->id);
556 if (successor_id == -1) {
557 XBT_INFO("Cannot join the ring.");
560 set_finger(node, 0, successor_id);
561 print_finger_table(node);
564 return successor_id != -1;
568 * \brief Makes the current node quit the system
569 * \param node the current node
571 static void leave(node_t node)
573 XBT_DEBUG("Well Guys! I Think it's time for me to quit ;)");
575 RngStream_DeleteStream(&node->stream);
579 * \brief Notifies the successor and the predecessor of the current node
581 * \param node the current node
583 static void quit_notify(node_t node)
585 char mailbox[MAILBOX_NAME_SIZE];
586 //send the PREDECESSOR_LEAVING to our successor
587 task_data_t req_data = xbt_new0(s_task_data_t,1);
588 req_data->type = TASK_PREDECESSOR_LEAVING;
589 req_data->request_id = node->pred_id;
590 get_mailbox(node->id, req_data->answer_to);
591 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
593 msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
594 XBT_DEBUG("Sending a 'PREDECESSOR_LEAVING' to my successor %d",node->fingers[0].id);
595 if (MSG_task_send_with_timeout(task_sent, node->fingers[0].mailbox, timeout)==
597 XBT_DEBUG("Timeout expired when sending a 'PREDECESSOR_LEAVING' to my successor %d",
598 node->fingers[0].id);
599 task_free(task_sent);
602 //send the SUCCESSOR_LEAVING to our predecessor
603 get_mailbox(node->pred_id, mailbox);
604 task_data_t req_data_s = xbt_new0(s_task_data_t,1);
605 req_data_s->type = TASK_SUCCESSOR_LEAVING;
606 req_data_s->request_id = node->fingers[0].id;
607 req_data_s->request_id = node->pred_id;
608 get_mailbox(node->id, req_data_s->answer_to);
609 req_data_s->issuer_host_name = MSG_host_get_name(MSG_host_self());
611 msg_task_t task_sent_s = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data_s);
612 XBT_DEBUG("Sending a 'SUCCESSOR_LEAVING' to my predecessor %d",node->pred_id);
613 if (MSG_task_send_with_timeout(task_sent_s, mailbox, timeout)==
615 XBT_DEBUG("Timeout expired when sending a 'SUCCESSOR_LEAVING' to my predecessor %d",
617 task_free(task_sent_s);
623 * \brief Makes the current node find the successor node of an id.
624 * \param node the current node
625 * \param id the id to find
626 * \return the id of the successor node, or -1 if the request failed
628 static int find_successor(node_t node, int id)
630 // is my successor the successor?
631 if (is_in_interval(id, node->id + 1, node->fingers[0].id)) {
632 return node->fingers[0].id;
635 // otherwise, ask the closest preceding finger in my table
636 int closest = closest_preceding_node(node, id);
637 return remote_find_successor(node, closest, id);
641 * \brief Asks another node the successor node of an id.
642 * \param node the current node
643 * \param ask_to the node to ask to
644 * \param id the id to find
645 * \return the id of the successor node, or -1 if the request failed
647 static int remote_find_successor(node_t node, int ask_to, int id)
651 char mailbox[MAILBOX_NAME_SIZE];
652 get_mailbox(ask_to, mailbox);
653 task_data_t req_data = xbt_new0(s_task_data_t, 1);
654 req_data->type = TASK_FIND_SUCCESSOR;
655 req_data->request_id = id;
656 get_mailbox(node->id, req_data->answer_to);
657 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
659 // send a "Find Successor" request to ask_to_id
660 msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
661 XBT_DEBUG("Sending a 'Find Successor' request (task %p) to %d for id %d", task_sent, ask_to, id);
662 msg_error_t res = MSG_task_send_with_timeout(task_sent, mailbox, timeout);
665 XBT_DEBUG("Failed to send the 'Find Successor' request (task %p) to %d for id %d",
666 task_sent, ask_to, id);
667 task_free(task_sent);
671 // receive the answer
672 XBT_DEBUG("Sent a 'Find Successor' request (task %p) to %d for key %d, waiting for the answer",
673 task_sent, ask_to, id);
676 if (node->comm_receive == NULL) {
677 msg_task_t task_received = NULL;
678 node->comm_receive = MSG_task_irecv(&task_received, node->mailbox);
681 res = MSG_comm_wait(node->comm_receive, timeout);
684 XBT_DEBUG("Failed to receive the answer to my 'Find Successor' request (task %p): %d",
685 task_sent, (int)res);
687 MSG_comm_destroy(node->comm_receive);
688 node->comm_receive = NULL;
691 msg_task_t task_received = MSG_comm_get_task(node->comm_receive);
692 XBT_DEBUG("Received a task (%p)", task_received);
693 task_data_t ans_data = MSG_task_get_data(task_received);
695 // Once upon a time, our code assumed that here, task_received != task_sent all the time
697 // This assumption is wrong (as messages from differing round can interleave), leading to a bug in our code.
698 // We failed to find this bug directly, as it only occured on large platforms, leading to hardly usable traces.
699 // Instead, we used the model-checker to track down the issue by adding the following test here in the code:
700 // if (MC_is_active()) {
701 // MC_assert(task_received == task_sent);
703 // That explained the bug in a snap, with a very cool example and everything.
705 // This MC_assert is now desactivated as the case is now properly handled in our code and we don't want the
706 // MC to fail any further under that condition, but this comment is here to as a memorial for this first
707 // brillant victory of the model-checking in the SimGrid community :)
709 if (task_received != task_sent) {
710 // this is not the expected answer
711 MSG_comm_destroy(node->comm_receive);
712 node->comm_receive = NULL;
713 handle_task(node, task_received);
716 // this is our answer
717 XBT_DEBUG("Received the answer to my 'Find Successor' request for id %d (task %p): the successor of key %d is %d",
718 ans_data->request_id, task_received, id, ans_data->answer_id);
719 successor = ans_data->answer_id;
721 MSG_comm_destroy(node->comm_receive);
722 node->comm_receive = NULL;
723 task_free(task_received);
733 * \brief Asks another node its predecessor.
734 * \param node the current node
735 * \param ask_to the node to ask to
736 * \return the id of its predecessor node, or -1 if the request failed
737 * (or if the node does not know its predecessor)
739 static int remote_get_predecessor(node_t node, int ask_to)
741 int predecessor_id = -1;
743 char mailbox[MAILBOX_NAME_SIZE];
744 get_mailbox(ask_to, mailbox);
745 task_data_t req_data = xbt_new0(s_task_data_t, 1);
746 req_data->type = TASK_GET_PREDECESSOR;
747 get_mailbox(node->id, req_data->answer_to);
748 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
750 // send a "Get Predecessor" request to ask_to_id
751 XBT_DEBUG("Sending a 'Get Predecessor' request to %d", ask_to);
752 msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
753 msg_error_t res = MSG_task_send_with_timeout(task_sent, mailbox, timeout);
756 XBT_DEBUG("Failed to send the 'Get Predecessor' request (task %p) to %d",
758 task_free(task_sent);
762 // receive the answer
763 XBT_DEBUG("Sent 'Get Predecessor' request (task %p) to %d, waiting for the answer on my mailbox '%s'",
764 task_sent, ask_to, req_data->answer_to);
767 if (node->comm_receive == NULL) { // FIXME simplify this
768 msg_task_t task_received = NULL;
769 node->comm_receive = MSG_task_irecv(&task_received, node->mailbox);
772 res = MSG_comm_wait(node->comm_receive, timeout);
775 XBT_DEBUG("Failed to receive the answer to my 'Get Predecessor' request (task %p): %d",
776 task_sent, (int)res);
778 MSG_comm_destroy(node->comm_receive);
779 node->comm_receive = NULL;
782 msg_task_t task_received = MSG_comm_get_task(node->comm_receive);
783 task_data_t ans_data = MSG_task_get_data(task_received);
785 /*if (MC_is_active()) {
786 MC_assert(task_received == task_sent);
789 if (task_received != task_sent) {
790 MSG_comm_destroy(node->comm_receive);
791 node->comm_receive = NULL;
792 handle_task(node, task_received);
795 XBT_DEBUG("Received the answer to my 'Get Predecessor' request (task %p): the predecessor of node %d is %d",
796 task_received, ask_to, ans_data->answer_id);
797 predecessor_id = ans_data->answer_id;
799 MSG_comm_destroy(node->comm_receive);
800 node->comm_receive = NULL;
801 task_free(task_received);
807 return predecessor_id;
811 * \brief Returns the closest preceding finger of an id
812 * with respect to the finger table of the current node.
813 * \param node the current node
814 * \param id the id to find
815 * \return the closest preceding finger of that id
817 int closest_preceding_node(node_t node, int id)
820 for (i = nb_bits - 1; i >= 0; i--) {
821 if (is_in_interval(node->fingers[i].id, node->id + 1, id - 1)) {
822 return node->fingers[i].id;
829 * \brief This function is called periodically. It checks the immediate
830 * successor of the current node.
831 * \param node the current node
833 static void stabilize(node_t node)
835 XBT_DEBUG("Stabilizing node");
837 // get the predecessor of my immediate successor
839 int successor_id = node->fingers[0].id;
840 if (successor_id != node->id) {
841 candidate_id = remote_get_predecessor(node, successor_id);
844 candidate_id = node->pred_id;
847 // this node is a candidate to become my new successor
848 if (candidate_id != -1
849 && is_in_interval(candidate_id, node->id + 1, successor_id - 1)) {
850 set_finger(node, 0, candidate_id);
852 if (successor_id != node->id) {
853 remote_notify(node, successor_id, node->id);
858 * \brief Notifies the current node that its predecessor may have changed.
859 * \param node the current node
860 * \param candidate_id the possible new predecessor
862 static void notify(node_t node, int predecessor_candidate_id) {
864 if (node->pred_id == -1
865 || is_in_interval(predecessor_candidate_id, node->pred_id + 1, node->id - 1)) {
867 set_predecessor(node, predecessor_candidate_id);
868 print_finger_table(node);
871 XBT_DEBUG("I don't have to change my predecessor to %d", predecessor_candidate_id);
876 * \brief Notifies a remote node that its predecessor may have changed.
877 * \param node the current node
878 * \param notify_id id of the node to notify
879 * \param candidate_id the possible new predecessor
881 static void remote_notify(node_t node, int notify_id, int predecessor_candidate_id) {
883 task_data_t req_data = xbt_new0(s_task_data_t, 1);
884 req_data->type = TASK_NOTIFY;
885 req_data->request_id = predecessor_candidate_id;
886 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
888 // send a "Notify" request to notify_id
889 msg_task_t task = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
890 XBT_DEBUG("Sending a 'Notify' request (task %p) to %d", task, notify_id);
891 char mailbox[MAILBOX_NAME_SIZE];
892 get_mailbox(notify_id, mailbox);
893 MSG_task_dsend(task, mailbox, task_free);
897 * \brief This function is called periodically.
898 * It refreshes the finger table of the current node.
899 * \param node the current node
901 static void fix_fingers(node_t node) {
903 XBT_DEBUG("Fixing fingers");
904 int i = node->next_finger_to_fix;
905 int id = find_successor(node, node->id + powers2[i]);
908 if (id != node->fingers[i].id) {
909 set_finger(node, i, id);
910 print_finger_table(node);
912 node->next_finger_to_fix = (i + 1) % nb_bits;
917 * \brief This function is called periodically.
918 * It checks whether the predecessor has failed
919 * \param node the current node
921 static void check_predecessor(node_t node)
923 XBT_DEBUG("Checking whether my predecessor is alive");
925 if(node->pred_id == -1)
930 char mailbox[MAILBOX_NAME_SIZE];
931 get_mailbox(node->pred_id, mailbox);
932 task_data_t req_data = xbt_new0(s_task_data_t,1);
933 req_data->type = TASK_PREDECESSOR_ALIVE;
934 req_data->request_id = node->pred_id;
935 get_mailbox(node->id, req_data->answer_to);
936 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
938 msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
939 XBT_DEBUG("Sending a 'Predecessor Alive' request to my predecessor %d", node->pred_id);
941 msg_error_t res = MSG_task_send_with_timeout(task_sent, mailbox, timeout);
944 XBT_DEBUG("Failed to send the 'Predecessor Alive' request (task %p) to %d", task_sent, node->pred_id);
945 task_free(task_sent);
948 // receive the answer
949 XBT_DEBUG("Sent 'Predecessor Alive' request (task %p) to %d, waiting for the answer on my mailbox '%s'",
950 task_sent, node->pred_id, req_data->answer_to);
953 if (node->comm_receive == NULL) { // FIXME simplify this
954 msg_task_t task_received = NULL;
955 node->comm_receive = MSG_task_irecv(&task_received, node->mailbox);
958 res = MSG_comm_wait(node->comm_receive, timeout);
961 XBT_DEBUG("Failed to receive the answer to my 'Predecessor Alive' request (task %p): %d",
962 task_sent, (int)res);
964 MSG_comm_destroy(node->comm_receive);
965 node->comm_receive = NULL;
968 msg_task_t task_received = MSG_comm_get_task(node->comm_receive);
969 if (task_received != task_sent) {
970 MSG_comm_destroy(node->comm_receive);
971 node->comm_receive = NULL;
972 handle_task(node, task_received);
974 XBT_DEBUG("Received the answer to my 'Predecessor Alive' request (task %p) : my predecessor %d is alive", task_received, node->pred_id);
976 MSG_comm_destroy(node->comm_receive);
977 node->comm_receive = NULL;
978 task_free(task_received);
986 * \brief Performs a find successor request to a random id.
987 * \param node the current node
989 static void random_lookup(node_t node)
993 find_successor(node, id);
995 /*** Random lookup disabled for tesh examples ***/
996 /*if(node->stream == NULL)
997 node->stream = RngStream_CreateStream("");
998 int random_index = RngStream_RandInt (node->stream, 0, nb_bits - 1);
999 int random_id = node->fingers[random_index].id;
1000 XBT_DEBUG("Making a lookup request for id %d", random_id);
1001 int res = find_successor(node, random_id);
1002 XBT_DEBUG("The successor of node %d is %d", random_id, res);*/
1007 * \brief Main function.
1009 int main(int argc, char *argv[])
1011 MSG_init(&argc, argv);
1013 printf("Usage: %s [-nb_bits=n] [-timeout=t] platform_file deployment_file\n", argv[0]);
1014 printf("example: %s ../msg_platform.xml chord.xml\n", argv[0]);
1018 char **options = &argv[1];
1019 while (!strncmp(options[0], "-", 1)) {
1021 int length = strlen("-nb_bits=");
1022 if (!strncmp(options[0], "-nb_bits=", length) && strlen(options[0]) > length) {
1023 nb_bits = atoi(options[0] + length);
1024 XBT_DEBUG("Set nb_bits to %d", nb_bits);
1028 length = strlen("-timeout=");
1029 if (!strncmp(options[0], "-timeout=", length) && strlen(options[0]) > length) {
1030 timeout = atoi(options[0] + length);
1031 XBT_DEBUG("Set timeout to %d", timeout);
1034 xbt_die("Invalid chord option '%s'", options[0]);
1040 const char* platform_file = options[0];
1041 const char* application_file = options[1];
1045 MSG_create_environment(platform_file);
1047 MSG_function_register("node", node);
1048 MSG_launch_application(application_file);
1050 msg_error_t res = MSG_main();
1051 XBT_CRITICAL("Messages created: %ld", smx_total_comms);
1052 XBT_INFO("Simulated time: %g", MSG_get_clock());