2 /* Copyright (c) 2010. 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"
14 /** @addtogroup MSG_examples
16 * - <b>chord/chord.c: Classical Chord P2P protocol</b>
17 * This example implements the well known Chord P2P protocol. Its
18 * main advantage is that it constitute a fully working non-trivial
19 * example. In addition, its implementation is rather efficient, as
20 * demonstrated in http://hal.inria.fr/inria-00602216/
24 XBT_LOG_NEW_DEFAULT_CATEGORY(msg_chord,
25 "Messages specific for this msg example");
29 #define MAILBOX_NAME_SIZE 10
31 static int nb_bits = 24;
32 static int nb_keys = 0;
33 static int timeout = 50;
34 static int max_simulation_time = 1000;
35 static int periodic_stabilize_delay = 20;
36 static int periodic_fix_fingers_delay = 120;
37 static int periodic_check_predecessor_delay = 120;
38 static int periodic_lookup_delay = 10;
40 extern long int smx_total_comms;
45 typedef struct s_finger {
47 char mailbox[MAILBOX_NAME_SIZE]; // string representation of the id
48 } s_finger_t, *finger_t;
53 typedef struct s_node {
55 char mailbox[MAILBOX_NAME_SIZE]; // my mailbox name (string representation of the id)
56 s_finger_t *fingers; // finger table, of size nb_bits (fingers[0] is my successor)
57 int pred_id; // predecessor id
58 char pred_mailbox[MAILBOX_NAME_SIZE]; // predecessor's mailbox name
59 int next_finger_to_fix; // index of the next finger to fix in fix_fingers()
60 msg_comm_t comm_receive; // current communication to receive
61 double last_change_date; // last time I changed a finger or my predecessor
65 * Types of tasks exchanged between nodes.
69 TASK_FIND_SUCCESSOR_ANSWER,
71 TASK_GET_PREDECESSOR_ANSWER,
73 TASK_SUCCESSOR_LEAVING,
74 TASK_PREDECESSOR_LEAVING
78 * Data attached with the tasks sent and received
80 typedef struct s_task_data {
81 e_task_type_t type; // type of task
82 int request_id; // id paramater (used by some types of tasks)
83 int request_finger; // finger parameter (used by some types of tasks)
84 int answer_id; // answer (used by some types of tasks)
85 char answer_to[MAILBOX_NAME_SIZE]; // mailbox to send an answer to (if any)
86 const char* issuer_host_name; // used for logging
87 } s_task_data_t, *task_data_t;
92 static void chord_initialize(void);
93 static void chord_exit(void);
94 static int normalize(int id);
95 static int is_in_interval(int id, int start, int end);
96 static void get_mailbox(int host_id, char* mailbox);
97 static void task_free(void* task);
98 static void print_finger_table(node_t node);
99 static void set_finger(node_t node, int finger_index, int id);
100 static void set_predecessor(node_t node, int predecessor_id);
103 static int node(int argc, char *argv[]);
104 static void handle_task(node_t node, msg_task_t task);
107 static void create(node_t node);
108 static int join(node_t node, int known_id);
109 static void leave(node_t node);
110 static int find_successor(node_t node, int id);
111 static int remote_find_successor(node_t node, int ask_to_id, int id);
112 static int remote_get_predecessor(node_t node, int ask_to_id);
113 static int closest_preceding_node(node_t node, int id);
114 static void stabilize(node_t node);
115 static void notify(node_t node, int predecessor_candidate_id);
116 static void remote_notify(node_t node, int notify_to, int predecessor_candidate_id);
117 static void fix_fingers(node_t node);
118 static void check_predecessor(node_t node);
119 static void random_lookup(node_t);
120 static void quit_notify(node_t node);
123 * \brief Global initialization of the Chord simulation.
125 static void chord_initialize(void)
127 // compute the powers of 2 once for all
128 powers2 = xbt_new(int, nb_bits);
131 for (i = 0; i < nb_bits; i++) {
136 XBT_DEBUG("Sets nb_keys to %d", nb_keys);
139 static void chord_exit(void)
145 * \brief Turns an id into an equivalent id in [0, nb_keys).
147 * \return the corresponding normalized id
149 static int normalize(int id)
151 // like id % nb_keys, but works with negatives numbers (and faster)
152 return id & (nb_keys - 1);
156 * \brief Returns whether an id belongs to the interval [start, end].
158 * The parameters are noramlized to make sure they are between 0 and nb_keys - 1).
159 * 1 belongs to [62, 3]
160 * 1 does not belong to [3, 62]
161 * 63 belongs to [62, 3]
162 * 63 does not belong to [3, 62]
163 * 24 belongs to [21, 29]
164 * 24 does not belong to [29, 21]
166 * \param id id to check
167 * \param start lower bound
168 * \param end upper bound
169 * \return a non-zero value if id in in [start, end]
171 static int is_in_interval(int id, int start, int end)
174 start = normalize(start);
175 end = normalize(end);
177 // make sure end >= start and id >= start
190 * \brief Gets the mailbox name of a host given its chord id.
191 * \param node_id id of a node
192 * \param mailbox pointer to where the mailbox name should be written
193 * (there must be enough space)
195 static void get_mailbox(int node_id, char* mailbox)
197 snprintf(mailbox, MAILBOX_NAME_SIZE - 1, "%d", node_id);
201 * \brief Frees the memory used by a task.
202 * \param task the MSG task to destroy
204 static void task_free(void* task)
206 // TODO add a parameter data_free_function to MSG_task_create?
208 xbt_free(MSG_task_get_data(task));
209 MSG_task_destroy(task);
214 * \brief Displays the finger table of a node.
217 static void print_finger_table(node_t node)
219 if (XBT_LOG_ISENABLED(msg_chord, xbt_log_priority_verbose)) {
221 XBT_VERB("My finger table:");
222 XBT_VERB("Start | Succ ");
223 for (i = 0; i < nb_bits; i++) {
224 XBT_VERB(" %3d | %3d ", (node->id + powers2[i]) % nb_keys, node->fingers[i].id);
226 XBT_VERB("Predecessor: %d", node->pred_id);
231 * \brief Sets a finger of the current node.
232 * \param node the current node
233 * \param finger_index index of the finger to set (0 to nb_bits - 1)
234 * \param id the id to set for this finger
236 static void set_finger(node_t node, int finger_index, int id)
238 if (id != node->fingers[finger_index].id) {
239 node->fingers[finger_index].id = id;
240 get_mailbox(id, node->fingers[finger_index].mailbox);
241 node->last_change_date = MSG_get_clock();
242 XBT_DEBUG("My new finger #%d is %d", finger_index, id);
247 * \brief Sets the predecessor of the current node.
248 * \param node the current node
249 * \param id the id to predecessor, or -1 to unset the predecessor
251 static void set_predecessor(node_t node, int predecessor_id)
253 if (predecessor_id != node->pred_id) {
254 node->pred_id = predecessor_id;
256 if (predecessor_id != -1) {
257 get_mailbox(predecessor_id, node->pred_mailbox);
259 node->last_change_date = MSG_get_clock();
261 XBT_DEBUG("My new predecessor is %d", predecessor_id);
266 * \brief Node Function
269 * - the id of a guy I know in the system (except for the first node)
270 * - the time to sleep before I join (except for the first node)
272 int node(int argc, char *argv[])
275 /* Reduce the run size for the MC */
277 periodic_stabilize_delay = 8;
278 periodic_fix_fingers_delay = 8;
279 periodic_check_predecessor_delay = 8;
282 double init_time = MSG_get_clock();
283 msg_task_t task_received = NULL;
285 int join_success = 0;
287 double next_stabilize_date = init_time + periodic_stabilize_delay;
288 double next_fix_fingers_date = init_time + periodic_fix_fingers_delay;
289 double next_check_predecessor_date = init_time + periodic_check_predecessor_delay;
290 double next_lookup_date = init_time + periodic_lookup_delay;
292 xbt_assert(argc == 3 || argc == 5, "Wrong number of arguments for this node");
294 // initialize my node
296 node.id = atoi(argv[1]);
297 get_mailbox(node.id, node.mailbox);
298 node.next_finger_to_fix = 0;
299 node.fingers = xbt_new0(s_finger_t, nb_bits);
300 node.last_change_date = init_time;
302 for (i = 0; i < nb_bits; i++) {
303 node.fingers[i].id = -1;
304 set_finger(&node, i, node.id);
307 if (argc == 3) { // first ring
308 deadline = atof(argv[2]);
313 int known_id = atoi(argv[2]);
314 //double sleep_time = atof(argv[3]);
315 deadline = atof(argv[4]);
318 // sleep before starting
319 XBT_DEBUG("Let's sleep during %f", sleep_time);
320 MSG_process_sleep(sleep_time);
322 XBT_DEBUG("Hey! Let's join the system.");
324 join_success = join(&node, known_id);
328 while (MSG_get_clock() < init_time + deadline
329 // && MSG_get_clock() < node.last_change_date + 1000
330 && MSG_get_clock() < max_simulation_time) {
332 if (node.comm_receive == NULL) {
333 task_received = NULL;
334 node.comm_receive = MSG_task_irecv(&task_received, node.mailbox);
335 // FIXME: do not make MSG_task_irecv() calls from several functions
338 if (!MSG_comm_test(node.comm_receive)) {
340 // no task was received: make some periodic calls
346 }else if(MC_random()){
348 }else if(MC_random()){
349 check_predecessor(&node);
350 }else if(MC_random()){
351 random_lookup(&node);
353 MSG_process_sleep(5);
356 if (MSG_get_clock() >= next_stabilize_date) {
358 next_stabilize_date = MSG_get_clock() + periodic_stabilize_delay;
360 else if (MSG_get_clock() >= next_fix_fingers_date) {
362 next_fix_fingers_date = MSG_get_clock() + periodic_fix_fingers_delay;
364 else if (MSG_get_clock() >= next_check_predecessor_date) {
365 check_predecessor(&node);
366 next_check_predecessor_date = MSG_get_clock() + periodic_check_predecessor_delay;
368 else if (MSG_get_clock() >= next_lookup_date) {
369 random_lookup(&node);
370 next_lookup_date = MSG_get_clock() + periodic_lookup_delay;
373 // nothing to do: sleep for a while
374 MSG_process_sleep(5);
378 if (MSG_get_clock() >= next_stabilize_date) {
380 next_stabilize_date = MSG_get_clock() + periodic_stabilize_delay;
382 else if (MSG_get_clock() >= next_fix_fingers_date) {
384 next_fix_fingers_date = MSG_get_clock() + periodic_fix_fingers_delay;
386 else if (MSG_get_clock() >= next_check_predecessor_date) {
387 check_predecessor(&node);
388 next_check_predecessor_date = MSG_get_clock() + periodic_check_predecessor_delay;
390 else if (MSG_get_clock() >= next_lookup_date) {
391 random_lookup(&node);
392 next_lookup_date = MSG_get_clock() + periodic_lookup_delay;
395 // nothing to do: sleep for a while
396 MSG_process_sleep(5);
401 // a transfer has occurred
403 msg_error_t status = MSG_comm_get_status(node.comm_receive);
405 if (status != MSG_OK) {
406 XBT_DEBUG("Failed to receive a task. Nevermind.");
407 MSG_comm_destroy(node.comm_receive);
408 node.comm_receive = NULL;
411 // the task was successfully received
412 MSG_comm_destroy(node.comm_receive);
413 node.comm_receive = NULL;
414 handle_task(&node, task_received);
419 if (node.comm_receive) {
420 MSG_comm_destroy(node.comm_receive);
421 node.comm_receive = NULL;
428 // stop the simulation
429 xbt_free(node.fingers);
434 * \brief This function is called when the current node receives a task.
435 * \param node the current node
436 * \param task the task to handle (don't touch it then:
437 * it will be destroyed, reused or forwarded)
439 static void handle_task(node_t node, msg_task_t task) {
441 XBT_DEBUG("Handling task %p", task);
442 char mailbox[MAILBOX_NAME_SIZE];
443 task_data_t task_data = (task_data_t) MSG_task_get_data(task);
444 e_task_type_t type = task_data->type;
448 case TASK_FIND_SUCCESSOR:
449 XBT_DEBUG("Receiving a 'Find Successor' request from %s for id %d",
450 task_data->issuer_host_name, task_data->request_id);
451 // is my successor the successor?
452 if (is_in_interval(task_data->request_id, node->id + 1, node->fingers[0].id)) {
453 task_data->type = TASK_FIND_SUCCESSOR_ANSWER;
454 task_data->answer_id = node->fingers[0].id;
455 XBT_DEBUG("Sending back a 'Find Successor Answer' to %s (mailbox %s): the successor of %d is %d",
456 task_data->issuer_host_name,
457 task_data->answer_to,
458 task_data->request_id, task_data->answer_id);
459 MSG_task_dsend(task, task_data->answer_to, task_free);
462 // otherwise, forward the request to the closest preceding finger in my table
463 int closest = closest_preceding_node(node, task_data->request_id);
464 XBT_DEBUG("Forwarding the 'Find Successor' request for id %d to my closest preceding finger %d",
465 task_data->request_id, closest);
466 get_mailbox(closest, mailbox);
467 MSG_task_dsend(task, mailbox, task_free);
471 case TASK_GET_PREDECESSOR:
472 XBT_DEBUG("Receiving a 'Get Predecessor' request from %s", task_data->issuer_host_name);
473 task_data->type = TASK_GET_PREDECESSOR_ANSWER;
474 task_data->answer_id = node->pred_id;
475 XBT_DEBUG("Sending back a 'Get Predecessor Answer' to %s via mailbox '%s': my predecessor is %d",
476 task_data->issuer_host_name,
477 task_data->answer_to, task_data->answer_id);
478 MSG_task_dsend(task, task_data->answer_to, task_free);
482 // someone is telling me that he may be my new predecessor
483 XBT_DEBUG("Receiving a 'Notify' request from %s", task_data->issuer_host_name);
484 notify(node, task_data->request_id);
488 case TASK_PREDECESSOR_LEAVING:
489 // my predecessor is about to quit
490 XBT_DEBUG("Receiving a 'Predecessor Leaving' message from %s", task_data->issuer_host_name);
491 // modify my predecessor
492 set_predecessor(node, task_data->request_id);
495 >> notify my new predecessor
496 >> send a notify_predecessors !!
500 case TASK_SUCCESSOR_LEAVING:
501 // my successor is about to quit
502 XBT_DEBUG("Receiving a 'Successor Leaving' message from %s", task_data->issuer_host_name);
503 // modify my successor FIXME : this should be implicit ?
504 set_finger(node, 0, task_data->request_id);
507 >> notify my new successor
508 >> update my table & predecessors table */
511 case TASK_FIND_SUCCESSOR_ANSWER:
512 case TASK_GET_PREDECESSOR_ANSWER:
513 XBT_DEBUG("Ignoring unexpected task of type %d (%p)", (int)type, task);
520 * \brief Initializes the current node as the first one of the system.
521 * \param node the current node
523 static void create(node_t node)
525 XBT_DEBUG("Create a new Chord ring...");
526 set_predecessor(node, -1); // -1 means that I have no predecessor
527 print_finger_table(node);
531 * \brief Makes the current node join the ring, knowing the id of a node
532 * already in the ring
533 * \param node the current node
534 * \param known_id id of a node already in the ring
535 * \return 1 if the join operation succeeded, 0 otherwise
537 static int join(node_t node, int known_id)
539 XBT_INFO("Joining the ring with id %d, knowing node %d", node->id, known_id);
540 set_predecessor(node, -1); // no predecessor (yet)
544 for (i = 0; i < nb_bits; i++) {
545 set_finger(node, i, known_id);
549 int successor_id = remote_find_successor(node, known_id, node->id);
550 if (successor_id == -1) {
551 XBT_INFO("Cannot join the ring.");
554 set_finger(node, 0, successor_id);
555 print_finger_table(node);
558 return successor_id != -1;
562 * \brief Makes the current node quit the system
563 * \param node the current node
565 static void leave(node_t node)
567 XBT_DEBUG("Well Guys! I Think it's time for me to quit ;)");
572 * \brief Notifies the successor and the predecessor of the current node
574 * \param node the current node
576 static void quit_notify(node_t node)
578 char mailbox[MAILBOX_NAME_SIZE];
579 //send the PREDECESSOR_LEAVING to our successor
580 task_data_t req_data = xbt_new0(s_task_data_t,1);
581 req_data->type = TASK_PREDECESSOR_LEAVING;
582 req_data->request_id = node->pred_id;
583 get_mailbox(node->id, req_data->answer_to);
584 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
586 msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
587 XBT_DEBUG("Sending a 'PREDECESSOR_LEAVING' to my successor %d",node->fingers[0].id);
588 MSG_task_send_with_timeout(task_sent, node->fingers[0].mailbox, timeout);
590 //send the SUCCESSOR_LEAVING to our predecessor
591 get_mailbox(node->pred_id, mailbox);
592 task_data_t req_data_s = xbt_new0(s_task_data_t,1);
593 req_data_s->type = TASK_SUCCESSOR_LEAVING;
594 req_data_s->request_id = node->fingers[0].id;
595 req_data_s->request_id = node->pred_id;
596 get_mailbox(node->id, req_data_s->answer_to);
597 req_data_s->issuer_host_name = MSG_host_get_name(MSG_host_self());
599 msg_task_t task_sent_s = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data_s);
600 XBT_DEBUG("Sending a 'SUCCESSOR_LEAVING' to my predecessor %d",node->pred_id);
601 MSG_task_send_with_timeout(task_sent_s, mailbox, timeout);
606 * \brief Makes the current node find the successor node of an id.
607 * \param node the current node
608 * \param id the id to find
609 * \return the id of the successor node, or -1 if the request failed
611 static int find_successor(node_t node, int id)
613 // is my successor the successor?
614 if (is_in_interval(id, node->id + 1, node->fingers[0].id)) {
615 return node->fingers[0].id;
618 // otherwise, ask the closest preceding finger in my table
619 int closest = closest_preceding_node(node, id);
620 return remote_find_successor(node, closest, id);
624 * \brief Asks another node the successor node of an id.
625 * \param node the current node
626 * \param ask_to the node to ask to
627 * \param id the id to find
628 * \return the id of the successor node, or -1 if the request failed
630 static int remote_find_successor(node_t node, int ask_to, int id)
634 char mailbox[MAILBOX_NAME_SIZE];
635 get_mailbox(ask_to, mailbox);
636 task_data_t req_data = xbt_new0(s_task_data_t, 1);
637 req_data->type = TASK_FIND_SUCCESSOR;
638 req_data->request_id = id;
639 get_mailbox(node->id, req_data->answer_to);
640 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
642 // send a "Find Successor" request to ask_to_id
643 msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
644 XBT_DEBUG("Sending a 'Find Successor' request (task %p) to %d for id %d", task_sent, ask_to, id);
645 msg_error_t res = MSG_task_send_with_timeout(task_sent, mailbox, timeout);
648 XBT_DEBUG("Failed to send the 'Find Successor' request (task %p) to %d for id %d",
649 task_sent, ask_to, id);
650 task_free(task_sent);
654 // receive the answer
655 XBT_DEBUG("Sent a 'Find Successor' request (task %p) to %d for key %d, waiting for the answer",
656 task_sent, ask_to, id);
659 if (node->comm_receive == NULL) {
660 msg_task_t task_received = NULL;
661 node->comm_receive = MSG_task_irecv(&task_received, node->mailbox);
664 res = MSG_comm_wait(node->comm_receive, timeout);
667 XBT_DEBUG("Failed to receive the answer to my 'Find Successor' request (task %p): %d",
668 task_sent, (int)res);
670 MSG_comm_destroy(node->comm_receive);
671 node->comm_receive = NULL;
674 msg_task_t task_received = MSG_comm_get_task(node->comm_receive);
675 XBT_DEBUG("Received a task (%p)", task_received);
676 task_data_t ans_data = MSG_task_get_data(task_received);
678 // Once upon a time, our code assumed that here, task_received != task_sent all the time
680 // This assumption is wrong (as messages from differing round can interleave), leading to a bug in our code.
681 // We failed to find this bug directly, as it only occured on large platforms, leading to hardly usable traces.
682 // Instead, we used the model-checker to track down the issue by adding the following test here in the code:
683 // if (MC_is_active()) {
684 // MC_assert(task_received == task_sent);
686 // That explained the bug in a snap, with a very cool example and everything.
688 // This MC_assert is now desactivated as the case is now properly handled in our code and we don't want the
689 // MC to fail any further under that condition, but this comment is here to as a memorial for this first
690 // brillant victory of the model-checking in the SimGrid community :)
692 if (task_received != task_sent) {
693 // this is not the expected answer
694 MSG_comm_destroy(node->comm_receive);
695 node->comm_receive = NULL;
696 handle_task(node, task_received);
699 // this is our answer
700 XBT_DEBUG("Received the answer to my 'Find Successor' request for id %d (task %p): the successor of key %d is %d",
701 ans_data->request_id, task_received, id, ans_data->answer_id);
702 successor = ans_data->answer_id;
704 MSG_comm_destroy(node->comm_receive);
705 node->comm_receive = NULL;
706 task_free(task_received);
716 * \brief Asks another node its predecessor.
717 * \param node the current node
718 * \param ask_to the node to ask to
719 * \return the id of its predecessor node, or -1 if the request failed
720 * (or if the node does not know its predecessor)
722 static int remote_get_predecessor(node_t node, int ask_to)
724 int predecessor_id = -1;
726 char mailbox[MAILBOX_NAME_SIZE];
727 get_mailbox(ask_to, mailbox);
728 task_data_t req_data = xbt_new0(s_task_data_t, 1);
729 req_data->type = TASK_GET_PREDECESSOR;
730 get_mailbox(node->id, req_data->answer_to);
731 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
733 // send a "Get Predecessor" request to ask_to_id
734 XBT_DEBUG("Sending a 'Get Predecessor' request to %d", ask_to);
735 msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
736 msg_error_t res = MSG_task_send_with_timeout(task_sent, mailbox, timeout);
739 XBT_DEBUG("Failed to send the 'Get Predecessor' request (task %p) to %d",
741 task_free(task_sent);
745 // receive the answer
746 XBT_DEBUG("Sent 'Get Predecessor' request (task %p) to %d, waiting for the answer on my mailbox '%s'",
747 task_sent, ask_to, req_data->answer_to);
750 if (node->comm_receive == NULL) { // FIXME simplify this
751 msg_task_t task_received = NULL;
752 node->comm_receive = MSG_task_irecv(&task_received, node->mailbox);
755 res = MSG_comm_wait(node->comm_receive, timeout);
758 XBT_DEBUG("Failed to receive the answer to my 'Get Predecessor' request (task %p): %d",
759 task_sent, (int)res);
761 MSG_comm_destroy(node->comm_receive);
762 node->comm_receive = NULL;
765 msg_task_t task_received = MSG_comm_get_task(node->comm_receive);
766 task_data_t ans_data = MSG_task_get_data(task_received);
768 if (MC_is_active()) {
769 MC_assert(task_received == task_sent);
772 if (task_received != task_sent) {
773 MSG_comm_destroy(node->comm_receive);
774 node->comm_receive = NULL;
775 handle_task(node, task_received);
778 XBT_DEBUG("Received the answer to my 'Get Predecessor' request (task %p): the predecessor of node %d is %d",
779 task_received, ask_to, ans_data->answer_id);
780 predecessor_id = ans_data->answer_id;
782 MSG_comm_destroy(node->comm_receive);
783 node->comm_receive = NULL;
784 task_free(task_received);
790 return predecessor_id;
794 * \brief Returns the closest preceding finger of an id
795 * with respect to the finger table of the current node.
796 * \param node the current node
797 * \param id the id to find
798 * \return the closest preceding finger of that id
800 int closest_preceding_node(node_t node, int id)
803 for (i = nb_bits - 1; i >= 0; i--) {
804 if (is_in_interval(node->fingers[i].id, node->id + 1, id - 1)) {
805 return node->fingers[i].id;
812 * \brief This function is called periodically. It checks the immediate
813 * successor of the current node.
814 * \param node the current node
816 static void stabilize(node_t node)
818 XBT_DEBUG("Stabilizing node");
820 // get the predecessor of my immediate successor
822 int successor_id = node->fingers[0].id;
823 if (successor_id != node->id) {
824 candidate_id = remote_get_predecessor(node, successor_id);
827 candidate_id = node->pred_id;
830 // this node is a candidate to become my new successor
831 if (candidate_id != -1
832 && is_in_interval(candidate_id, node->id + 1, successor_id - 1)) {
833 set_finger(node, 0, candidate_id);
835 if (successor_id != node->id) {
836 remote_notify(node, successor_id, node->id);
841 * \brief Notifies the current node that its predecessor may have changed.
842 * \param node the current node
843 * \param candidate_id the possible new predecessor
845 static void notify(node_t node, int predecessor_candidate_id) {
847 if (node->pred_id == -1
848 || is_in_interval(predecessor_candidate_id, node->pred_id + 1, node->id - 1)) {
850 set_predecessor(node, predecessor_candidate_id);
851 print_finger_table(node);
854 XBT_DEBUG("I don't have to change my predecessor to %d", predecessor_candidate_id);
859 * \brief Notifies a remote node that its predecessor may have changed.
860 * \param node the current node
861 * \param notify_id id of the node to notify
862 * \param candidate_id the possible new predecessor
864 static void remote_notify(node_t node, int notify_id, int predecessor_candidate_id) {
866 task_data_t req_data = xbt_new0(s_task_data_t, 1);
867 req_data->type = TASK_NOTIFY;
868 req_data->request_id = predecessor_candidate_id;
869 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
871 // send a "Notify" request to notify_id
872 msg_task_t task = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
873 XBT_DEBUG("Sending a 'Notify' request (task %p) to %d", task, notify_id);
874 char mailbox[MAILBOX_NAME_SIZE];
875 get_mailbox(notify_id, mailbox);
876 MSG_task_dsend(task, mailbox, task_free);
880 * \brief This function is called periodically.
881 * It refreshes the finger table of the current node.
882 * \param node the current node
884 static void fix_fingers(node_t node) {
886 XBT_DEBUG("Fixing fingers");
887 int i = node->next_finger_to_fix;
888 int id = find_successor(node, node->id + powers2[i]);
891 if (id != node->fingers[i].id) {
892 set_finger(node, i, id);
893 print_finger_table(node);
895 node->next_finger_to_fix = (i + 1) % nb_bits;
900 * \brief This function is called periodically.
901 * It checks whether the predecessor has failed
902 * \param node the current node
904 static void check_predecessor(node_t node)
906 XBT_DEBUG("Checking whether my predecessor is alive");
911 * \brief Performs a find successor request to a random id.
912 * \param node the current node
914 static void random_lookup(node_t node)
916 int id = 1337; // TODO pick a pseudorandom id
917 XBT_DEBUG("Making a lookup request for id %d", id);
918 find_successor(node, id);
922 * \brief Main function.
924 int main(int argc, char *argv[])
926 MSG_init(&argc, argv);
928 printf("Usage: %s [-nb_bits=n] [-timeout=t] platform_file deployment_file\n", argv[0]);
929 printf("example: %s ../msg_platform.xml chord.xml\n", argv[0]);
933 char **options = &argv[1];
934 while (!strncmp(options[0], "-", 1)) {
936 int length = strlen("-nb_bits=");
937 if (!strncmp(options[0], "-nb_bits=", length) && strlen(options[0]) > length) {
938 nb_bits = atoi(options[0] + length);
939 XBT_DEBUG("Set nb_bits to %d", nb_bits);
943 length = strlen("-timeout=");
944 if (!strncmp(options[0], "-timeout=", length) && strlen(options[0]) > length) {
945 timeout = atoi(options[0] + length);
946 XBT_DEBUG("Set timeout to %d", timeout);
949 xbt_die("Invalid chord option '%s'", options[0]);
955 const char* platform_file = options[0];
956 const char* application_file = options[1];
960 MSG_create_environment(platform_file);
962 MSG_function_register("node", node);
963 MSG_launch_application(application_file);
965 msg_error_t res = MSG_main();
966 XBT_CRITICAL("Messages created: %ld", smx_total_comms);
967 XBT_INFO("Simulated time: %g", MSG_get_clock());