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"
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;
296 xbt_assert(argc == 3 || argc == 5, "Wrong number of arguments for this node");
298 // initialize my node
300 node.id = atoi(argv[1]);
301 get_mailbox(node.id, node.mailbox);
302 node.next_finger_to_fix = 0;
303 node.fingers = xbt_new0(s_finger_t, nb_bits);
304 node.last_change_date = init_time;
306 for (i = 0; i < nb_bits; i++) {
307 node.fingers[i].id = -1;
308 set_finger(&node, i, node.id);
311 if (argc == 3) { // first ring
312 deadline = atof(argv[2]);
317 int known_id = atoi(argv[2]);
318 //double sleep_time = atof(argv[3]);
319 deadline = atof(argv[4]);
322 // sleep before starting
323 XBT_DEBUG("Let's sleep during %f", sleep_time);
324 MSG_process_sleep(sleep_time);
326 XBT_DEBUG("Hey! Let's join the system.");
328 join_success = join(&node, known_id);
332 while (MSG_get_clock() < init_time + deadline
333 // && MSG_get_clock() < node.last_change_date + 1000
334 && MSG_get_clock() < max_simulation_time) {
336 if (node.comm_receive == NULL) {
337 task_received = NULL;
338 node.comm_receive = MSG_task_irecv(&task_received, node.mailbox);
339 // FIXME: do not make MSG_task_irecv() calls from several functions
342 if (!MSG_comm_test(node.comm_receive)) {
344 // no task was received: make some periodic calls
350 }else if(MC_random()){
352 }else if(MC_random()){
353 check_predecessor(&node);
354 }else if(MC_random()){
355 random_lookup(&node);
357 MSG_process_sleep(5);
360 if (MSG_get_clock() >= next_stabilize_date) {
362 next_stabilize_date = MSG_get_clock() + periodic_stabilize_delay;
364 else if (MSG_get_clock() >= next_fix_fingers_date) {
366 next_fix_fingers_date = MSG_get_clock() + periodic_fix_fingers_delay;
368 else if (MSG_get_clock() >= next_check_predecessor_date) {
369 check_predecessor(&node);
370 next_check_predecessor_date = MSG_get_clock() + periodic_check_predecessor_delay;
372 else if (MSG_get_clock() >= next_lookup_date) {
373 random_lookup(&node);
374 next_lookup_date = MSG_get_clock() + periodic_lookup_delay;
377 // nothing to do: sleep for a while
378 MSG_process_sleep(5);
382 if (MSG_get_clock() >= next_stabilize_date) {
384 next_stabilize_date = MSG_get_clock() + periodic_stabilize_delay;
386 else if (MSG_get_clock() >= next_fix_fingers_date) {
388 next_fix_fingers_date = MSG_get_clock() + periodic_fix_fingers_delay;
390 else if (MSG_get_clock() >= next_check_predecessor_date) {
391 check_predecessor(&node);
392 next_check_predecessor_date = MSG_get_clock() + periodic_check_predecessor_delay;
394 else if (MSG_get_clock() >= next_lookup_date) {
395 random_lookup(&node);
396 next_lookup_date = MSG_get_clock() + periodic_lookup_delay;
399 // nothing to do: sleep for a while
400 MSG_process_sleep(5);
405 // a transfer has occurred
407 msg_error_t status = MSG_comm_get_status(node.comm_receive);
409 if (status != MSG_OK) {
410 XBT_DEBUG("Failed to receive a task. Nevermind.");
411 MSG_comm_destroy(node.comm_receive);
412 node.comm_receive = NULL;
415 // the task was successfully received
416 MSG_comm_destroy(node.comm_receive);
417 node.comm_receive = NULL;
418 handle_task(&node, task_received);
423 if (node.comm_receive) {
424 MSG_comm_destroy(node.comm_receive);
425 node.comm_receive = NULL;
432 // stop the simulation
433 xbt_free(node.fingers);
438 * \brief This function is called when the current node receives a task.
439 * \param node the current node
440 * \param task the task to handle (don't touch it then:
441 * it will be destroyed, reused or forwarded)
443 static void handle_task(node_t node, msg_task_t task) {
445 XBT_DEBUG("Handling task %p", task);
446 char mailbox[MAILBOX_NAME_SIZE];
447 task_data_t task_data = (task_data_t) MSG_task_get_data(task);
448 e_task_type_t type = task_data->type;
452 case TASK_FIND_SUCCESSOR:
453 XBT_DEBUG("Receiving a 'Find Successor' request from %s for id %d",
454 task_data->issuer_host_name, task_data->request_id);
455 // is my successor the successor?
456 if (is_in_interval(task_data->request_id, node->id + 1, node->fingers[0].id)) {
457 task_data->type = TASK_FIND_SUCCESSOR_ANSWER;
458 task_data->answer_id = node->fingers[0].id;
459 XBT_DEBUG("Sending back a 'Find Successor Answer' to %s (mailbox %s): the successor of %d is %d",
460 task_data->issuer_host_name,
461 task_data->answer_to,
462 task_data->request_id, task_data->answer_id);
463 MSG_task_dsend(task, task_data->answer_to, task_free);
466 // otherwise, forward the request to the closest preceding finger in my table
467 int closest = closest_preceding_node(node, task_data->request_id);
468 XBT_DEBUG("Forwarding the 'Find Successor' request for id %d to my closest preceding finger %d",
469 task_data->request_id, closest);
470 get_mailbox(closest, mailbox);
471 MSG_task_dsend(task, mailbox, task_free);
475 case TASK_GET_PREDECESSOR:
476 XBT_DEBUG("Receiving a 'Get Predecessor' request from %s", task_data->issuer_host_name);
477 task_data->type = TASK_GET_PREDECESSOR_ANSWER;
478 task_data->answer_id = node->pred_id;
479 XBT_DEBUG("Sending back a 'Get Predecessor Answer' to %s via mailbox '%s': my predecessor is %d",
480 task_data->issuer_host_name,
481 task_data->answer_to, task_data->answer_id);
482 MSG_task_dsend(task, task_data->answer_to, task_free);
486 // someone is telling me that he may be my new predecessor
487 XBT_DEBUG("Receiving a 'Notify' request from %s", task_data->issuer_host_name);
488 notify(node, task_data->request_id);
492 case TASK_PREDECESSOR_LEAVING:
493 // my predecessor is about to quit
494 XBT_DEBUG("Receiving a 'Predecessor Leaving' message from %s", task_data->issuer_host_name);
495 // modify my predecessor
496 set_predecessor(node, task_data->request_id);
499 >> notify my new predecessor
500 >> send a notify_predecessors !!
504 case TASK_SUCCESSOR_LEAVING:
505 // my successor is about to quit
506 XBT_DEBUG("Receiving a 'Successor Leaving' message from %s", task_data->issuer_host_name);
507 // modify my successor FIXME : this should be implicit ?
508 set_finger(node, 0, task_data->request_id);
511 >> notify my new successor
512 >> update my table & predecessors table */
515 case TASK_FIND_SUCCESSOR_ANSWER:
516 case TASK_GET_PREDECESSOR_ANSWER:
517 case TASK_PREDECESSOR_ALIVE_ANSWER:
518 XBT_DEBUG("Ignoring unexpected task of type %d (%p)", (int)type, task);
522 case TASK_PREDECESSOR_ALIVE:
523 XBT_DEBUG("Receiving a 'Predecessor Alive' request from %s", task_data->issuer_host_name);
524 task_data->type = TASK_PREDECESSOR_ALIVE_ANSWER;
525 XBT_DEBUG("Sending back a 'Predecessor Alive Answer' to %s (mailbox %s)",
526 task_data->issuer_host_name,
527 task_data->answer_to);
528 MSG_task_dsend(task, task_data->answer_to, task_free);
535 * \brief Initializes the current node as the first one of the system.
536 * \param node the current node
538 static void create(node_t node)
540 XBT_DEBUG("Create a new Chord ring...");
541 set_predecessor(node, -1); // -1 means that I have no predecessor
542 print_finger_table(node);
546 * \brief Makes the current node join the ring, knowing the id of a node
547 * already in the ring
548 * \param node the current node
549 * \param known_id id of a node already in the ring
550 * \return 1 if the join operation succeeded, 0 otherwise
552 static int join(node_t node, int known_id)
554 XBT_INFO("Joining the ring with id %d, knowing node %d", node->id, known_id);
555 set_predecessor(node, -1); // no predecessor (yet)
559 for (i = 0; i < nb_bits; i++) {
560 set_finger(node, i, known_id);
564 int successor_id = remote_find_successor(node, known_id, node->id);
565 if (successor_id == -1) {
566 XBT_INFO("Cannot join the ring.");
569 set_finger(node, 0, successor_id);
570 print_finger_table(node);
573 return successor_id != -1;
577 * \brief Makes the current node quit the system
578 * \param node the current node
580 static void leave(node_t node)
582 XBT_DEBUG("Well Guys! I Think it's time for me to quit ;)");
584 RngStream_DeleteStream(&node->stream);
588 * \brief Notifies the successor and the predecessor of the current node
590 * \param node the current node
592 static void quit_notify(node_t node)
594 char mailbox[MAILBOX_NAME_SIZE];
595 //send the PREDECESSOR_LEAVING to our successor
596 task_data_t req_data = xbt_new0(s_task_data_t,1);
597 req_data->type = TASK_PREDECESSOR_LEAVING;
598 req_data->request_id = node->pred_id;
599 get_mailbox(node->id, req_data->answer_to);
600 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
602 msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
603 XBT_DEBUG("Sending a 'PREDECESSOR_LEAVING' to my successor %d",node->fingers[0].id);
604 MSG_task_send_with_timeout(task_sent, node->fingers[0].mailbox, timeout);
606 //send the SUCCESSOR_LEAVING to our predecessor
607 get_mailbox(node->pred_id, mailbox);
608 task_data_t req_data_s = xbt_new0(s_task_data_t,1);
609 req_data_s->type = TASK_SUCCESSOR_LEAVING;
610 req_data_s->request_id = node->fingers[0].id;
611 req_data_s->request_id = node->pred_id;
612 get_mailbox(node->id, req_data_s->answer_to);
613 req_data_s->issuer_host_name = MSG_host_get_name(MSG_host_self());
615 msg_task_t task_sent_s = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data_s);
616 XBT_DEBUG("Sending a 'SUCCESSOR_LEAVING' to my predecessor %d",node->pred_id);
617 MSG_task_send_with_timeout(task_sent_s, mailbox, timeout);
622 * \brief Makes the current node find the successor node of an id.
623 * \param node the current node
624 * \param id the id to find
625 * \return the id of the successor node, or -1 if the request failed
627 static int find_successor(node_t node, int id)
629 // is my successor the successor?
630 if (is_in_interval(id, node->id + 1, node->fingers[0].id)) {
631 return node->fingers[0].id;
634 // otherwise, ask the closest preceding finger in my table
635 int closest = closest_preceding_node(node, id);
636 return remote_find_successor(node, closest, id);
640 * \brief Asks another node the successor node of an id.
641 * \param node the current node
642 * \param ask_to the node to ask to
643 * \param id the id to find
644 * \return the id of the successor node, or -1 if the request failed
646 static int remote_find_successor(node_t node, int ask_to, int id)
650 char mailbox[MAILBOX_NAME_SIZE];
651 get_mailbox(ask_to, mailbox);
652 task_data_t req_data = xbt_new0(s_task_data_t, 1);
653 req_data->type = TASK_FIND_SUCCESSOR;
654 req_data->request_id = id;
655 get_mailbox(node->id, req_data->answer_to);
656 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
658 // send a "Find Successor" request to ask_to_id
659 msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
660 XBT_DEBUG("Sending a 'Find Successor' request (task %p) to %d for id %d", task_sent, ask_to, id);
661 msg_error_t res = MSG_task_send_with_timeout(task_sent, mailbox, timeout);
664 XBT_DEBUG("Failed to send the 'Find Successor' request (task %p) to %d for id %d",
665 task_sent, ask_to, id);
666 task_free(task_sent);
670 // receive the answer
671 XBT_DEBUG("Sent a 'Find Successor' request (task %p) to %d for key %d, waiting for the answer",
672 task_sent, ask_to, id);
675 if (node->comm_receive == NULL) {
676 msg_task_t task_received = NULL;
677 node->comm_receive = MSG_task_irecv(&task_received, node->mailbox);
680 res = MSG_comm_wait(node->comm_receive, timeout);
683 XBT_DEBUG("Failed to receive the answer to my 'Find Successor' request (task %p): %d",
684 task_sent, (int)res);
686 MSG_comm_destroy(node->comm_receive);
687 node->comm_receive = NULL;
690 msg_task_t task_received = MSG_comm_get_task(node->comm_receive);
691 XBT_DEBUG("Received a task (%p)", task_received);
692 task_data_t ans_data = MSG_task_get_data(task_received);
694 // Once upon a time, our code assumed that here, task_received != task_sent all the time
696 // This assumption is wrong (as messages from differing round can interleave), leading to a bug in our code.
697 // We failed to find this bug directly, as it only occured on large platforms, leading to hardly usable traces.
698 // Instead, we used the model-checker to track down the issue by adding the following test here in the code:
699 // if (MC_is_active()) {
700 // MC_assert(task_received == task_sent);
702 // That explained the bug in a snap, with a very cool example and everything.
704 // This MC_assert is now desactivated as the case is now properly handled in our code and we don't want the
705 // MC to fail any further under that condition, but this comment is here to as a memorial for this first
706 // brillant victory of the model-checking in the SimGrid community :)
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");
924 if(node->pred_id == -1)
929 char mailbox[MAILBOX_NAME_SIZE];
930 get_mailbox(node->pred_id, mailbox);
931 task_data_t req_data = xbt_new0(s_task_data_t,1);
932 req_data->type = TASK_PREDECESSOR_ALIVE;
933 req_data->request_id = node->pred_id;
934 get_mailbox(node->id, req_data->answer_to);
935 req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
937 msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
938 XBT_DEBUG("Sending a 'Predecessor Alive' request to my predecessor %d", node->pred_id);
940 msg_error_t res = MSG_task_send_with_timeout(task_sent, mailbox, timeout);
943 XBT_DEBUG("Failed to send the 'Predecessor Alive' request (task %p) to %d", task_sent, node->pred_id);
944 task_free(task_sent);
947 // receive the answer
948 XBT_DEBUG("Sent 'Predecessor Alive' request (task %p) to %d, waiting for the answer on my mailbox '%s'",
949 task_sent, node->pred_id, req_data->answer_to);
952 if (node->comm_receive == NULL) { // FIXME simplify this
953 msg_task_t task_received = NULL;
954 node->comm_receive = MSG_task_irecv(&task_received, node->mailbox);
957 res = MSG_comm_wait(node->comm_receive, timeout);
960 XBT_DEBUG("Failed to receive the answer to my 'Predecessor Alive' request (task %p): %d",
961 task_sent, (int)res);
963 MSG_comm_destroy(node->comm_receive);
964 node->comm_receive = NULL;
967 msg_task_t task_received = MSG_comm_get_task(node->comm_receive);
968 if (task_received != task_sent) {
969 MSG_comm_destroy(node->comm_receive);
970 node->comm_receive = NULL;
971 handle_task(node, task_received);
973 XBT_DEBUG("Received the answer to my 'Predecessor Alive' request (task %p) : my predecessor %d is alive", task_received, node->pred_id);
975 MSG_comm_destroy(node->comm_receive);
976 node->comm_receive = NULL;
977 task_free(task_received);
985 * \brief Performs a find successor request to a random id.
986 * \param node the current node
988 static void random_lookup(node_t node)
992 find_successor(node, id);
994 /*** Random lookup disabled for tesh examples ***/
995 /*if(node->stream == NULL)
996 node->stream = RngStream_CreateStream("");
997 int random_index = RngStream_RandInt (node->stream, 0, nb_bits - 1);
998 int random_id = node->fingers[random_index].id;
999 XBT_DEBUG("Making a lookup request for id %d", random_id);
1000 int res = find_successor(node, random_id);
1001 XBT_DEBUG("The successor of node %d is %d", random_id, res);*/
1006 * \brief Main function.
1008 int main(int argc, char *argv[])
1010 MSG_init(&argc, argv);
1012 printf("Usage: %s [-nb_bits=n] [-timeout=t] platform_file deployment_file\n", argv[0]);
1013 printf("example: %s ../msg_platform.xml chord.xml\n", argv[0]);
1017 char **options = &argv[1];
1018 while (!strncmp(options[0], "-", 1)) {
1020 int length = strlen("-nb_bits=");
1021 if (!strncmp(options[0], "-nb_bits=", length) && strlen(options[0]) > length) {
1022 nb_bits = atoi(options[0] + length);
1023 XBT_DEBUG("Set nb_bits to %d", nb_bits);
1027 length = strlen("-timeout=");
1028 if (!strncmp(options[0], "-timeout=", length) && strlen(options[0]) > length) {
1029 timeout = atoi(options[0] + length);
1030 XBT_DEBUG("Set timeout to %d", timeout);
1033 xbt_die("Invalid chord option '%s'", options[0]);
1039 const char* platform_file = options[0];
1040 const char* application_file = options[1];
1044 MSG_create_environment(platform_file);
1046 MSG_function_register("node", node);
1047 MSG_launch_application(application_file);
1049 msg_error_t res = MSG_main();
1050 XBT_CRITICAL("Messages created: %ld", smx_total_comms);
1051 XBT_INFO("Simulated time: %g", MSG_get_clock());