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"
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(chord_liveness,
26 "Messages specific for this 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
66 * Types of tasks exchanged between nodes.
70 TASK_FIND_SUCCESSOR_ANSWER,
72 TASK_GET_PREDECESSOR_ANSWER,
74 TASK_SUCCESSOR_LEAVING,
75 TASK_PREDECESSOR_LEAVING
79 * Data attached with the tasks sent and received
81 typedef struct s_task_data {
82 e_task_type_t type; // type of task
83 int request_id; // id paramater (used by some types of tasks)
84 int request_finger; // finger parameter (used by some types of tasks)
85 int answer_id; // answer (used by some types of tasks)
86 char answer_to[MAILBOX_NAME_SIZE]; // mailbox to send an answer to (if any)
87 const char* issuer_host_name; // used for logging
88 } s_task_data_t, *task_data_t;
93 static void chord_initialize(void);
94 static void chord_exit(void);
95 static int normalize(int id);
96 static int is_in_interval(int id, int start, int end);
97 static void get_mailbox(int host_id, char* mailbox);
98 static void task_free(void* task);
99 static void print_finger_table(node_t node);
100 static void set_finger(node_t node, int finger_index, int id);
101 static void set_predecessor(node_t node, int predecessor_id);
104 static int node(int argc, char *argv[]);
105 static void handle_task(node_t node, msg_task_t task);
108 static void create(node_t node);
109 static int join(node_t node, int known_id);
110 static void leave(node_t node);
111 static int find_successor(node_t node, int id);
112 static int remote_find_successor(node_t node, int ask_to_id, int id);
113 static int remote_get_predecessor(node_t node, int ask_to_id);
114 static int closest_preceding_node(node_t node, int id);
115 static void stabilize(node_t node);
116 static void notify(node_t node, int predecessor_candidate_id);
117 static void remote_notify(node_t node, int notify_to, int predecessor_candidate_id);
118 static void fix_fingers(node_t node);
119 static void check_predecessor(node_t node);
120 static void random_lookup(node_t);
121 static void quit_notify(node_t node);
123 /* Global variables corresponding to atomic propositions */
125 int node_deliver = 0;
128 * \brief Global initialization of the Chord simulation.
130 static void chord_initialize(void)
132 // compute the powers of 2 once for all
133 powers2 = xbt_new(int, nb_bits);
136 for (i = 0; i < nb_bits; i++) {
141 XBT_DEBUG("Sets nb_keys to %d", nb_keys);
144 static void chord_exit(void)
150 * \brief Turns an id into an equivalent id in [0, nb_keys).
152 * \return the corresponding normalized id
154 static int normalize(int id)
156 // like id % nb_keys, but works with negatives numbers (and faster)
157 return id & (nb_keys - 1);
161 * \brief Returns whether an id belongs to the interval [start, end].
163 * The parameters are noramlized to make sure they are between 0 and nb_keys - 1).
164 * 1 belongs to [62, 3]
165 * 1 does not belong to [3, 62]
166 * 63 belongs to [62, 3]
167 * 63 does not belong to [3, 62]
168 * 24 belongs to [21, 29]
169 * 24 does not belong to [29, 21]
171 * \param id id to check
172 * \param start lower bound
173 * \param end upper bound
174 * \return a non-zero value if id in in [start, end]
176 static int is_in_interval(int id, int start, int end)
179 start = normalize(start);
180 end = normalize(end);
182 // make sure end >= start and id >= start
195 * \brief Gets the mailbox name of a host given its chord id.
196 * \param node_id id of a node
197 * \param mailbox pointer to where the mailbox name should be written
198 * (there must be enough space)
200 static void get_mailbox(int node_id, char* mailbox)
202 snprintf(mailbox, MAILBOX_NAME_SIZE - 1, "%d", node_id);
206 * \brief Frees the memory used by a task.
207 * \param task the MSG task to destroy
209 static void task_free(void* task)
211 // TODO add a parameter data_free_function to MSG_task_create?
213 xbt_free(MSG_task_get_data(task));
214 MSG_task_destroy(task);
220 * \brief Displays the finger table of a node.
223 static void print_finger_table(node_t node)
225 if (XBT_LOG_ISENABLED(chord_liveness, xbt_log_priority_verbose)) {
227 XBT_VERB("My finger table:");
228 XBT_VERB("Start | Succ ");
229 for (i = 0; i < nb_bits; i++) {
230 XBT_VERB(" %3d | %3d ", (node->id + powers2[i]) % nb_keys, node->fingers[i].id);
232 XBT_VERB("Predecessor: %d", node->pred_id);
237 * \brief Sets a finger of the current node.
238 * \param node the current node
239 * \param finger_index index of the finger to set (0 to nb_bits - 1)
240 * \param id the id to set for this finger
242 static void set_finger(node_t node, int finger_index, int id)
244 if (id != node->fingers[finger_index].id) {
245 node->fingers[finger_index].id = id;
246 get_mailbox(id, node->fingers[finger_index].mailbox);
247 node->last_change_date = MSG_get_clock();
248 XBT_DEBUG("My new finger #%d is %d", finger_index, id);
253 * \brief Sets the predecessor of the current node.
254 * \param node the current node
255 * \param id the id to predecessor, or -1 to unset the predecessor
257 static void set_predecessor(node_t node, int predecessor_id)
259 if (predecessor_id != node->pred_id) {
260 node->pred_id = predecessor_id;
262 if (predecessor_id != -1) {
263 get_mailbox(predecessor_id, node->pred_mailbox);
265 node->last_change_date = MSG_get_clock();
267 XBT_DEBUG("My new predecessor is %d", predecessor_id);
272 * \brief Node Function
275 * - the id of a guy I know in the system (except for the first node)
276 * - the time to sleep before I join (except for the first node)
278 int node(int argc, char *argv[])
280 /* Reduce the run size for the MC */
282 periodic_stabilize_delay = 8;
283 periodic_fix_fingers_delay = 8;
284 periodic_check_predecessor_delay = 8;
287 double init_time = MSG_get_clock();
288 msg_task_t task_received = NULL;
290 int join_success = 0;
292 double next_stabilize_date = init_time + periodic_stabilize_delay;
293 double next_fix_fingers_date = init_time + periodic_fix_fingers_delay;
294 double next_check_predecessor_date = init_time + periodic_check_predecessor_delay;
295 double next_lookup_date = init_time + periodic_lookup_delay;
297 xbt_assert(argc == 3 || argc == 5, "Wrong number of arguments for this node");
299 // initialize my node
301 node.id = atoi(argv[1]);
302 get_mailbox(node.id, node.mailbox);
303 node.next_finger_to_fix = 0;
304 node.fingers = xbt_new0(s_finger_t, nb_bits);
305 node.last_change_date = init_time;
307 for (i = 0; i < nb_bits; i++) {
308 node.fingers[i].id = -1;
309 set_finger(&node, i, node.id);
312 if (argc == 3) { // first ring
313 deadline = atof(argv[2]);
318 int known_id = atoi(argv[2]);
319 //double sleep_time = atof(argv[3]);
320 deadline = atof(argv[4]);
323 // sleep before starting
324 XBT_DEBUG("Let's sleep during %f", sleep_time);
325 MSG_process_sleep(sleep_time);
327 XBT_DEBUG("Hey! Let's join the system.");
329 join_success = join(&node, known_id);
332 XBT_INFO("Node %d joined the ring", node.id);
339 while (MSG_get_clock() < init_time + deadline
340 // && MSG_get_clock() < node.last_change_date + 1000
341 && MSG_get_clock() < max_simulation_time) {
343 if (node.comm_receive == NULL) {
344 task_received = NULL;
345 node.comm_receive = MSG_task_irecv(&task_received, node.mailbox);
346 // FIXME: do not make MSG_task_irecv() calls from several functions
349 if (!MSG_comm_test(node.comm_receive)) {
355 }else if(MC_random()){
357 }else if(MC_random()){
358 check_predecessor(&node);
359 }else if(MC_random()){
360 random_lookup(&node);
362 MSG_process_sleep(5);
365 if (MSG_get_clock() >= next_stabilize_date) {
367 next_stabilize_date = MSG_get_clock() + periodic_stabilize_delay;
369 else if (MSG_get_clock() >= next_fix_fingers_date) {
371 next_fix_fingers_date = MSG_get_clock() + periodic_fix_fingers_delay;
373 else if (MSG_get_clock() >= next_check_predecessor_date) {
374 check_predecessor(&node);
375 next_check_predecessor_date = MSG_get_clock() + periodic_check_predecessor_delay;
377 else if (MSG_get_clock() >= next_lookup_date) {
378 random_lookup(&node);
379 next_lookup_date = MSG_get_clock() + periodic_lookup_delay;
382 // nothing to do: sleep for a while
383 MSG_process_sleep(5);
387 if (MSG_get_clock() >= next_stabilize_date) {
389 next_stabilize_date = MSG_get_clock() + periodic_stabilize_delay;
391 else if (MSG_get_clock() >= next_fix_fingers_date) {
393 next_fix_fingers_date = MSG_get_clock() + periodic_fix_fingers_delay;
395 else if (MSG_get_clock() >= next_check_predecessor_date) {
396 check_predecessor(&node);
397 next_check_predecessor_date = MSG_get_clock() + periodic_check_predecessor_delay;
399 else if (MSG_get_clock() >= next_lookup_date) {
400 random_lookup(&node);
401 next_lookup_date = MSG_get_clock() + periodic_lookup_delay;
404 // nothing to do: sleep for a while
405 MSG_process_sleep(5);
411 if (node.comm_receive) {
415 XBT_INFO("A transfer has occured");
417 // a transfer has occured
419 msg_error_t status = MSG_comm_get_status(node.comm_receive);
421 if (status != MSG_OK) {
422 XBT_INFO("Failed to receive a task. Nevermind.");
423 MSG_comm_destroy(node.comm_receive);
424 node.comm_receive = NULL;
427 // the task was successfully received
428 XBT_INFO("The task was successfully received by node %d", node.id);
429 MSG_comm_destroy(node.comm_receive);
430 node.comm_receive = NULL;
431 handle_task(&node, task_received);
437 if (node.comm_receive) {
438 MSG_comm_destroy(node.comm_receive);
439 node.comm_receive = NULL;
446 // stop the simulation
447 xbt_free(node.fingers);
452 * \brief This function is called when the current node receives a task.
453 * \param node the current node
454 * \param task the task to handle (don't touch it then:
455 * it will be destroyed, reused or forwarded)
457 static void handle_task(node_t node, msg_task_t task) {
459 XBT_DEBUG("Handling task %p", task);
460 char mailbox[MAILBOX_NAME_SIZE];
461 task_data_t task_data = (task_data_t) MSG_task_get_data(task);
462 e_task_type_t type = task_data->type;
466 case TASK_FIND_SUCCESSOR:
468 XBT_DEBUG("Receiving a 'Find Successor' request from %s for id %d",
469 task_data->issuer_host_name, task_data->request_id);
470 // is my successor the successor?
471 if (is_in_interval(task_data->request_id, node->id + 1, node->fingers[0].id)) {
472 task_data->type = TASK_FIND_SUCCESSOR_ANSWER;
473 task_data->answer_id = node->fingers[0].id;
474 XBT_DEBUG("Sending back a 'Find Successor Answer' to %s (mailbox %s): the successor of %d is %d",
475 task_data->issuer_host_name,
476 task_data->answer_to,
477 task_data->request_id, task_data->answer_id);
478 MSG_task_dsend(task, task_data->answer_to, task_free);
481 // otherwise, forward the request to the closest preceding finger in my table
482 int closest = closest_preceding_node(node, task_data->request_id);
483 XBT_DEBUG("Forwarding the 'Find Successor' request for id %d to my closest preceding finger %d",
484 task_data->request_id, closest);
485 get_mailbox(closest, mailbox);
486 MSG_task_dsend(task, mailbox, task_free);
490 case TASK_GET_PREDECESSOR:
491 XBT_DEBUG("Receiving a 'Get Predecessor' request from %s", task_data->issuer_host_name);
492 task_data->type = TASK_GET_PREDECESSOR_ANSWER;
493 task_data->answer_id = node->pred_id;
494 XBT_DEBUG("Sending back a 'Get Predecessor Answer' to %s via mailbox '%s': my predecessor is %d",
495 task_data->issuer_host_name,
496 task_data->answer_to, task_data->answer_id);
497 MSG_task_dsend(task, task_data->answer_to, task_free);
501 // someone is telling me that he may be my new predecessor
502 XBT_DEBUG("Receiving a 'Notify' request from %s", task_data->issuer_host_name);
503 notify(node, task_data->request_id);
507 case TASK_PREDECESSOR_LEAVING:
508 // my predecessor is about to quit
509 XBT_DEBUG("Receiving a 'Predecessor Leaving' message from %s", task_data->issuer_host_name);
510 // modify my predecessor
511 set_predecessor(node, task_data->request_id);
514 >> notify my new predecessor
515 >> send a notify_predecessors !!
519 case TASK_SUCCESSOR_LEAVING:
520 // my successor is about to quit
521 XBT_DEBUG("Receiving a 'Successor Leaving' message from %s", task_data->issuer_host_name);
522 // modify my successor FIXME : this should be implicit ?
523 set_finger(node, 0, task_data->request_id);
526 >> notify my new successor
527 >> update my table & predecessors table */
530 case TASK_FIND_SUCCESSOR_ANSWER:
531 case TASK_GET_PREDECESSOR_ANSWER:
532 XBT_DEBUG("Ignoring unexpected task of type %d (%p)", (int)type, task);
539 * \brief Initializes the current node as the first one of the system.
540 * \param node the current node
542 static void create(node_t node)
544 XBT_DEBUG("Create a new Chord ring...");
545 set_predecessor(node, -1); // -1 means that I have no predecessor
546 print_finger_table(node);
550 * \brief Makes the current node join the ring, knowing the id of a node
551 * already in the ring
552 * \param node the current node
553 * \param known_id id of a node already in the ring
554 * \return 1 if the join operation succeeded, 0 otherwise
556 static int join(node_t node, int known_id)
558 XBT_INFO("Joining the ring with id %d, knowing node %d", node->id, known_id);
559 set_predecessor(node, -1); // no predecessor (yet)
563 for (i = 0; i < nb_bits; i++) {
564 set_finger(node, i, known_id);
568 int successor_id = remote_find_successor(node, known_id, node->id);
569 if (successor_id == -1) {
570 XBT_INFO("Cannot join the ring.");
573 set_finger(node, 0, successor_id);
574 print_finger_table(node);
577 return successor_id != -1;
581 * \brief Makes the current node quit the system
582 * \param node the current node
584 static void leave(node_t node)
586 XBT_DEBUG("Well Guys! I Think it's time for me to quit ;)");
591 * \brief Notifies the successor and the predecessor of the current node
593 * \param node the current node
595 static void quit_notify(node_t node)
597 char mailbox[MAILBOX_NAME_SIZE];
598 //send the PREDECESSOR_LEAVING to our successor
599 task_data_t req_data = xbt_new0(s_task_data_t,1);
600 req_data->type = TASK_PREDECESSOR_LEAVING;
601 req_data->request_id = node->pred_id;
602 get_mailbox(node->id, req_data->answer_to);
603 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
605 msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
606 XBT_DEBUG("Sending a 'PREDECESSOR_LEAVING' to my successor %d",node->fingers[0].id);
607 MSG_task_send_with_timeout(task_sent, node->fingers[0].mailbox, timeout);
609 //send the SUCCESSOR_LEAVING to our predecessor
610 get_mailbox(node->pred_id, mailbox);
611 task_data_t req_data_s = xbt_new0(s_task_data_t,1);
612 req_data_s->type = TASK_SUCCESSOR_LEAVING;
613 req_data_s->request_id = node->fingers[0].id;
614 req_data_s->request_id = node->pred_id;
615 get_mailbox(node->id, req_data_s->answer_to);
616 req_data_s->issuer_host_name = MSG_host_get_name(MSG_host_self());
618 msg_task_t task_sent_s = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data_s);
619 XBT_DEBUG("Sending a 'SUCCESSOR_LEAVING' to my predecessor %d",node->pred_id);
620 MSG_task_send_with_timeout(task_sent_s, mailbox, timeout);
625 * \brief Makes the current node find the successor node of an id.
626 * \param node the current node
627 * \param id the id to find
628 * \return the id of the successor node, or -1 if the request failed
630 static int find_successor(node_t node, int id)
632 // is my successor the successor?
633 if (is_in_interval(id, node->id + 1, node->fingers[0].id)) {
634 return node->fingers[0].id;
637 // otherwise, ask the closest preceding finger in my table
638 int closest = closest_preceding_node(node, id);
639 return remote_find_successor(node, closest, id);
643 * \brief Asks another node the successor node of an id.
644 * \param node the current node
645 * \param ask_to the node to ask to
646 * \param id the id to find
647 * \return the id of the successor node, or -1 if the request failed
649 static int remote_find_successor(node_t node, int ask_to, int id)
653 char mailbox[MAILBOX_NAME_SIZE];
654 get_mailbox(ask_to, mailbox);
655 task_data_t req_data = xbt_new0(s_task_data_t, 1);
656 req_data->type = TASK_FIND_SUCCESSOR;
657 req_data->request_id = id;
658 get_mailbox(node->id, req_data->answer_to);
659 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
661 // send a "Find Successor" request to ask_to_id
662 msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
663 XBT_DEBUG("Sending a 'Find Successor' request (task %p) to %d for id %d", task_sent, ask_to, id);
664 msg_error_t res = MSG_task_send_with_timeout(task_sent, mailbox, timeout);
667 XBT_DEBUG("Failed to send the 'Find Successor' request (task %p) to %d for id %d",
668 task_sent, ask_to, id);
669 task_free(task_sent);
673 // receive the answer
674 XBT_DEBUG("Sent a 'Find Successor' request (task %p) to %d for key %d, waiting for the answer",
675 task_sent, ask_to, id);
678 if (node->comm_receive == NULL) {
679 msg_task_t task_received = NULL;
680 node->comm_receive = MSG_task_irecv(&task_received, node->mailbox);
683 res = MSG_comm_wait(node->comm_receive, timeout);
686 XBT_DEBUG("Failed to receive the answer to my 'Find Successor' request (task %p): %d",
687 task_sent, (int)res);
689 MSG_comm_destroy(node->comm_receive);
690 node->comm_receive = NULL;
693 msg_task_t task_received = MSG_comm_get_task(node->comm_receive);
694 XBT_DEBUG("Received a task (%p)", task_received);
695 task_data_t ans_data = MSG_task_get_data(task_received);
697 if (MC_is_active()) {
698 // the model-checker is expected to find a counter-example here.
700 // As you can see in the test right below, task_received is not always equal to task_sent
701 // (as messages from differing round can interleave). But the previous version of this code
702 // wrongly assumed that, leading to problems. But this only occured on large platforms,
703 // leading to hardly usable traces. So we used the model-checker to track down the issue,
704 // and we came down to this test, that explained the bug in a snap.
705 //MC_assert(task_received == task_sent);
708 if (task_received != task_sent) {
709 // this is not the expected answer
710 MSG_comm_destroy(node->comm_receive);
711 node->comm_receive = NULL;
712 handle_task(node, task_received);
715 // this is our answer
716 XBT_DEBUG("Received the answer to my 'Find Successor' request for id %d (task %p): the successor of key %d is %d",
717 ans_data->request_id, task_received, id, ans_data->answer_id);
718 successor = ans_data->answer_id;
720 MSG_comm_destroy(node->comm_receive);
721 node->comm_receive = NULL;
722 task_free(task_received);
732 * \brief Asks another node its predecessor.
733 * \param node the current node
734 * \param ask_to the node to ask to
735 * \return the id of its predecessor node, or -1 if the request failed
736 * (or if the node does not know its predecessor)
738 static int remote_get_predecessor(node_t node, int ask_to)
740 int predecessor_id = -1;
742 char mailbox[MAILBOX_NAME_SIZE];
743 get_mailbox(ask_to, mailbox);
744 task_data_t req_data = xbt_new0(s_task_data_t, 1);
745 req_data->type = TASK_GET_PREDECESSOR;
746 get_mailbox(node->id, req_data->answer_to);
747 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
749 // send a "Get Predecessor" request to ask_to_id
750 XBT_DEBUG("Sending a 'Get Predecessor' request to %d", ask_to);
751 msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
752 msg_error_t res = MSG_task_send_with_timeout(task_sent, mailbox, timeout);
755 XBT_DEBUG("Failed to send the 'Get Predecessor' request (task %p) to %d",
757 task_free(task_sent);
761 // receive the answer
762 XBT_DEBUG("Sent 'Get Predecessor' request (task %p) to %d, waiting for the answer on my mailbox '%s'",
763 task_sent, ask_to, req_data->answer_to);
766 if (node->comm_receive == NULL) { // FIXME simplify this
767 msg_task_t task_received = NULL;
768 node->comm_receive = MSG_task_irecv(&task_received, node->mailbox);
771 res = MSG_comm_wait(node->comm_receive, timeout);
774 XBT_DEBUG("Failed to receive the answer to my 'Get Predecessor' request (task %p): %d",
775 task_sent, (int)res);
777 MSG_comm_destroy(node->comm_receive);
778 node->comm_receive = NULL;
781 msg_task_t task_received = MSG_comm_get_task(node->comm_receive);
782 task_data_t ans_data = MSG_task_get_data(task_received);
784 /*if (MC_is_active()) {
785 MC_assert(task_received == task_sent);
788 if (task_received != task_sent) {
789 MSG_comm_destroy(node->comm_receive);
790 node->comm_receive = NULL;
791 handle_task(node, task_received);
794 XBT_DEBUG("Received the answer to my 'Get Predecessor' request (task %p): the predecessor of node %d is %d",
795 task_received, ask_to, ans_data->answer_id);
796 predecessor_id = ans_data->answer_id;
798 MSG_comm_destroy(node->comm_receive);
799 node->comm_receive = NULL;
800 task_free(task_received);
806 return predecessor_id;
810 * \brief Returns the closest preceding finger of an id
811 * with respect to the finger table of the current node.
812 * \param node the current node
813 * \param id the id to find
814 * \return the closest preceding finger of that id
816 int closest_preceding_node(node_t node, int id)
819 for (i = nb_bits - 1; i >= 0; i--) {
820 if (is_in_interval(node->fingers[i].id, node->id + 1, id - 1)) {
821 return node->fingers[i].id;
828 * \brief This function is called periodically. It checks the immediate
829 * successor of the current node.
830 * \param node the current node
832 static void stabilize(node_t node)
834 XBT_DEBUG("Stabilizing node");
836 // get the predecessor of my immediate successor
838 int successor_id = node->fingers[0].id;
839 if (successor_id != node->id) {
840 candidate_id = remote_get_predecessor(node, successor_id);
843 candidate_id = node->pred_id;
846 // this node is a candidate to become my new successor
847 if (candidate_id != -1
848 && is_in_interval(candidate_id, node->id + 1, successor_id - 1)) {
849 set_finger(node, 0, candidate_id);
851 if (successor_id != node->id) {
852 remote_notify(node, successor_id, node->id);
857 * \brief Notifies the current node that its predecessor may have changed.
858 * \param node the current node
859 * \param candidate_id the possible new predecessor
861 static void notify(node_t node, int predecessor_candidate_id) {
863 if (node->pred_id == -1
864 || is_in_interval(predecessor_candidate_id, node->pred_id + 1, node->id - 1)) {
866 set_predecessor(node, predecessor_candidate_id);
867 print_finger_table(node);
870 XBT_DEBUG("I don't have to change my predecessor to %d", predecessor_candidate_id);
875 * \brief Notifies a remote node that its predecessor may have changed.
876 * \param node the current node
877 * \param notify_id id of the node to notify
878 * \param candidate_id the possible new predecessor
880 static void remote_notify(node_t node, int notify_id, int predecessor_candidate_id) {
882 task_data_t req_data = xbt_new0(s_task_data_t, 1);
883 req_data->type = TASK_NOTIFY;
884 req_data->request_id = predecessor_candidate_id;
885 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
887 // send a "Notify" request to notify_id
888 msg_task_t task = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
889 XBT_DEBUG("Sending a 'Notify' request (task %p) to %d", task, notify_id);
890 char mailbox[MAILBOX_NAME_SIZE];
891 get_mailbox(notify_id, mailbox);
892 MSG_task_dsend(task, mailbox, task_free);
896 * \brief This function is called periodically.
897 * It refreshes the finger table of the current node.
898 * \param node the current node
900 static void fix_fingers(node_t node) {
902 XBT_DEBUG("Fixing fingers");
903 int i = node->next_finger_to_fix;
904 int id = find_successor(node, node->id + powers2[i]);
907 if (id != node->fingers[i].id) {
908 set_finger(node, i, id);
909 print_finger_table(node);
911 node->next_finger_to_fix = (i + 1) % nb_bits;
916 * \brief This function is called periodically.
917 * It checks whether the predecessor has failed
918 * \param node the current node
920 static void check_predecessor(node_t node)
922 XBT_DEBUG("Checking whether my predecessor is alive");
927 * \brief Performs a find successor request to a random id.
928 * \param node the current node
930 static void random_lookup(node_t node)
932 int id = 1337; // TODO pick a pseudorandom id
933 XBT_DEBUG("Making a lookup request for id %d", id);
934 find_successor(node, id);
937 static int predJoin(void){
941 static int predDeliver(void){
947 * \brief Main function.
949 int main(int argc, char *argv[])
951 MSG_init(&argc, argv);
953 printf("Usage: %s [-nb_bits=n] [-timeout=t] platform_file deployment_file\n", argv[0]);
954 printf("example: %s ../../msg_platform.xml deploy_chord_liveness.xml\n", argv[0]);
958 char **options = &argv[1];
959 while (!strncmp(options[0], "-", 1)) {
961 int length = strlen("-nb_bits=");
962 if (!strncmp(options[0], "-nb_bits=", length) && strlen(options[0]) > length) {
963 nb_bits = atoi(options[0] + length);
964 XBT_DEBUG("Set nb_bits to %d", nb_bits);
968 length = strlen("-timeout=");
969 if (!strncmp(options[0], "-timeout=", length) && strlen(options[0]) > length) {
970 timeout = atoi(options[0] + length);
971 XBT_DEBUG("Set timeout to %d", timeout);
974 xbt_die("Invalid chord option '%s'", options[0]);
980 const char* platform_file = options[0];
981 const char* application_file = options[1];
985 MC_automaton_new_propositional_symbol("join", &predJoin);
986 MC_automaton_new_propositional_symbol("deliver", &predDeliver);
988 MSG_create_environment(platform_file);
990 MSG_function_register("node", node);
991 MSG_launch_application(application_file);
993 msg_error_t res = MSG_main();
994 XBT_INFO("Simulated time: %g", MSG_get_clock());