--- /dev/null
+
+/* Copyright (c) 2010. The SimGrid Team.
+ * All rights reserved. */
+
+/* This program is free software; you can redistribute it and/or modify it
+ * under the terms of the license (GNU LGPL) which comes with this package. */
+
+#include <stdio.h>
+#include "msg/msg.h"
+#include "xbt/log.h"
+#include "xbt/asserts.h"
+#include "simgrid/modelchecker.h"
+#include "mc/mc.h"
+
+/** @addtogroup MSG_examples
+ *
+ * - <b>chord/chord.c: Classical Chord P2P protocol</b>
+ * This example implements the well known Chord P2P protocol. Its
+ * main advantage is that it constitute a fully working non-trivial
+ * example. In addition, its implementation is rather efficient, as
+ * demonstrated in http://hal.inria.fr/inria-00602216/
+ */
+
+
+XBT_LOG_NEW_DEFAULT_CATEGORY(chord_liveness,
+ "Messages specific for this example");
+
+#define COMM_SIZE 10
+#define COMP_SIZE 0
+#define MAILBOX_NAME_SIZE 10
+
+static int nb_bits = 24;
+static int nb_keys = 0;
+static int timeout = 50;
+static int max_simulation_time = 1000;
+static int periodic_stabilize_delay = 20;
+static int periodic_fix_fingers_delay = 120;
+static int periodic_check_predecessor_delay = 120;
+static int periodic_lookup_delay = 10;
+
+//extern long int smx_total_comms;
+
+/*
+ * Finger element.
+ */
+typedef struct s_finger {
+ int id;
+ char mailbox[MAILBOX_NAME_SIZE]; // string representation of the id
+} s_finger_t, *finger_t;
+
+/*
+ * Node data.
+ */
+typedef struct s_node {
+ int id; // my id
+ char mailbox[MAILBOX_NAME_SIZE]; // my mailbox name (string representation of the id)
+ s_finger_t *fingers; // finger table, of size nb_bits (fingers[0] is my successor)
+ int pred_id; // predecessor id
+ char pred_mailbox[MAILBOX_NAME_SIZE]; // predecessor's mailbox name
+ int next_finger_to_fix; // index of the next finger to fix in fix_fingers()
+ msg_comm_t comm_receive; // current communication to receive
+ double last_change_date; // last time I changed a finger or my predecessor
+} s_node_t, *node_t;
+
+/**
+ * Types of tasks exchanged between nodes.
+ */
+typedef enum {
+ TASK_FIND_SUCCESSOR,
+ TASK_FIND_SUCCESSOR_ANSWER,
+ TASK_GET_PREDECESSOR,
+ TASK_GET_PREDECESSOR_ANSWER,
+ TASK_NOTIFY,
+ TASK_SUCCESSOR_LEAVING,
+ TASK_PREDECESSOR_LEAVING
+} e_task_type_t;
+
+/*
+ * Data attached with the tasks sent and received
+ */
+typedef struct s_task_data {
+ e_task_type_t type; // type of task
+ int request_id; // id paramater (used by some types of tasks)
+ int request_finger; // finger parameter (used by some types of tasks)
+ int answer_id; // answer (used by some types of tasks)
+ char answer_to[MAILBOX_NAME_SIZE]; // mailbox to send an answer to (if any)
+ const char* issuer_host_name; // used for logging
+} s_task_data_t, *task_data_t;
+
+static int *powers2;
+
+// utility functions
+static void chord_initialize(void);
+static void chord_exit(void);
+static int normalize(int id);
+static int is_in_interval(int id, int start, int end);
+static void get_mailbox(int host_id, char* mailbox);
+static void task_free(void* task);
+static void print_finger_table(node_t node);
+static void set_finger(node_t node, int finger_index, int id);
+static void set_predecessor(node_t node, int predecessor_id);
+
+// process functions
+static int node(int argc, char *argv[]);
+static void handle_task(node_t node, msg_task_t task);
+
+// Chord core
+static void create(node_t node);
+static int join(node_t node, int known_id);
+static void leave(node_t node);
+static int find_successor(node_t node, int id);
+static int remote_find_successor(node_t node, int ask_to_id, int id);
+static int remote_get_predecessor(node_t node, int ask_to_id);
+static int closest_preceding_node(node_t node, int id);
+static void stabilize(node_t node);
+static void notify(node_t node, int predecessor_candidate_id);
+static void remote_notify(node_t node, int notify_to, int predecessor_candidate_id);
+static void fix_fingers(node_t node);
+static void check_predecessor(node_t node);
+static void random_lookup(node_t);
+static void quit_notify(node_t node);
+
+/* Global variables corresponding to atomic propositions */
+int node_join = 0;
+int node_deliver = 0;
+
+/**
+ * \brief Global initialization of the Chord simulation.
+ */
+static void chord_initialize(void)
+{
+ // compute the powers of 2 once for all
+ powers2 = xbt_new(int, nb_bits);
+ int pow = 1;
+ int i;
+ for (i = 0; i < nb_bits; i++) {
+ powers2[i] = pow;
+ pow = pow << 1;
+ }
+ nb_keys = pow;
+ XBT_DEBUG("Sets nb_keys to %d", nb_keys);
+}
+
+static void chord_exit(void)
+{
+ xbt_free(powers2);
+}
+
+/**
+ * \brief Turns an id into an equivalent id in [0, nb_keys).
+ * \param id an id
+ * \return the corresponding normalized id
+ */
+static int normalize(int id)
+{
+ // like id % nb_keys, but works with negatives numbers (and faster)
+ return id & (nb_keys - 1);
+}
+
+/**
+ * \brief Returns whether an id belongs to the interval [start, end].
+ *
+ * The parameters are noramlized to make sure they are between 0 and nb_keys - 1).
+ * 1 belongs to [62, 3]
+ * 1 does not belong to [3, 62]
+ * 63 belongs to [62, 3]
+ * 63 does not belong to [3, 62]
+ * 24 belongs to [21, 29]
+ * 24 does not belong to [29, 21]
+ *
+ * \param id id to check
+ * \param start lower bound
+ * \param end upper bound
+ * \return a non-zero value if id in in [start, end]
+ */
+static int is_in_interval(int id, int start, int end)
+{
+ id = normalize(id);
+ start = normalize(start);
+ end = normalize(end);
+
+ // make sure end >= start and id >= start
+ if (end < start) {
+ end += nb_keys;
+ }
+
+ if (id < start) {
+ id += nb_keys;
+ }
+
+ return id <= end;
+}
+
+/**
+ * \brief Gets the mailbox name of a host given its chord id.
+ * \param node_id id of a node
+ * \param mailbox pointer to where the mailbox name should be written
+ * (there must be enough space)
+ */
+static void get_mailbox(int node_id, char* mailbox)
+{
+ snprintf(mailbox, MAILBOX_NAME_SIZE - 1, "%d", node_id);
+}
+
+/**
+ * \brief Frees the memory used by a task.
+ * \param task the MSG task to destroy
+ */
+static void task_free(void* task)
+{
+ // TODO add a parameter data_free_function to MSG_task_create?
+ if(task != NULL){
+ xbt_free(MSG_task_get_data(task));
+ MSG_task_destroy(task);
+ task = NULL;
+ }
+}
+
+/**
+ * \brief Displays the finger table of a node.
+ * \param node a node
+ */
+static void print_finger_table(node_t node)
+{
+ if (XBT_LOG_ISENABLED(chord_liveness, xbt_log_priority_verbose)) {
+ int i;
+ XBT_VERB("My finger table:");
+ XBT_VERB("Start | Succ ");
+ for (i = 0; i < nb_bits; i++) {
+ XBT_VERB(" %3d | %3d ", (node->id + powers2[i]) % nb_keys, node->fingers[i].id);
+ }
+ XBT_VERB("Predecessor: %d", node->pred_id);
+ }
+}
+
+/**
+ * \brief Sets a finger of the current node.
+ * \param node the current node
+ * \param finger_index index of the finger to set (0 to nb_bits - 1)
+ * \param id the id to set for this finger
+ */
+static void set_finger(node_t node, int finger_index, int id)
+{
+ if (id != node->fingers[finger_index].id) {
+ node->fingers[finger_index].id = id;
+ get_mailbox(id, node->fingers[finger_index].mailbox);
+ node->last_change_date = MSG_get_clock();
+ XBT_DEBUG("My new finger #%d is %d", finger_index, id);
+ }
+}
+
+/**
+ * \brief Sets the predecessor of the current node.
+ * \param node the current node
+ * \param id the id to predecessor, or -1 to unset the predecessor
+ */
+static void set_predecessor(node_t node, int predecessor_id)
+{
+ if (predecessor_id != node->pred_id) {
+ node->pred_id = predecessor_id;
+
+ if (predecessor_id != -1) {
+ get_mailbox(predecessor_id, node->pred_mailbox);
+ }
+ node->last_change_date = MSG_get_clock();
+
+ XBT_DEBUG("My new predecessor is %d", predecessor_id);
+ }
+}
+
+/**
+ * \brief Node Function
+ * Arguments:
+ * - my id
+ * - the id of a guy I know in the system (except for the first node)
+ * - the time to sleep before I join (except for the first node)
+ */
+int node(int argc, char *argv[])
+{
+ /* Reduce the run size for the MC */
+ if(MC_is_active()){
+ periodic_stabilize_delay = 8;
+ periodic_fix_fingers_delay = 8;
+ periodic_check_predecessor_delay = 8;
+ }
+
+ double init_time = MSG_get_clock();
+ msg_task_t task_received = NULL;
+ int i;
+ int join_success = 0;
+ double deadline;
+ double next_stabilize_date = init_time + periodic_stabilize_delay;
+ double next_fix_fingers_date = init_time + periodic_fix_fingers_delay;
+ double next_check_predecessor_date = init_time + periodic_check_predecessor_delay;
+ double next_lookup_date = init_time + periodic_lookup_delay;
+
+ xbt_assert(argc == 3 || argc == 5, "Wrong number of arguments for this node");
+
+ // initialize my node
+ s_node_t node = {0};
+ node.id = atoi(argv[1]);
+ get_mailbox(node.id, node.mailbox);
+ node.next_finger_to_fix = 0;
+ node.fingers = xbt_new0(s_finger_t, nb_bits);
+ node.last_change_date = init_time;
+
+ for (i = 0; i < nb_bits; i++) {
+ node.fingers[i].id = -1;
+ set_finger(&node, i, node.id);
+ }
+
+ if (argc == 3) { // first ring
+ deadline = atof(argv[2]);
+ create(&node);
+ join_success = 1;
+ }
+ else {
+ int known_id = atoi(argv[2]);
+ //double sleep_time = atof(argv[3]);
+ deadline = atof(argv[4]);
+
+ /*
+ // sleep before starting
+ XBT_DEBUG("Let's sleep during %f", sleep_time);
+ MSG_process_sleep(sleep_time);
+ */
+ XBT_DEBUG("Hey! Let's join the system.");
+
+ join_success = join(&node, known_id);
+
+ if(join_success){
+ XBT_INFO("Node %d joined the ring", node.id);
+ node_join = 1;
+ }
+ }
+
+ MC_assert(!node_join);
+
+ if (join_success) {
+
+ while (MSG_get_clock() < init_time + deadline
+// && MSG_get_clock() < node.last_change_date + 1000
+ && MSG_get_clock() < max_simulation_time) {
+
+ if (node.comm_receive == NULL) {
+ task_received = NULL;
+ node.comm_receive = MSG_task_irecv(&task_received, node.mailbox);
+ // FIXME: do not make MSG_task_irecv() calls from several functions
+ }
+
+ if (!MSG_comm_test(node.comm_receive)) {
+
+ #ifdef HAVE_MC
+ if(MC_is_active()){
+ if(MC_random()){
+ stabilize(&node);
+ }else if(MC_random()){
+ fix_fingers(&node);
+ }else if(MC_random()){
+ check_predecessor(&node);
+ }else if(MC_random()){
+ random_lookup(&node);
+ }else{
+ MSG_process_sleep(5);
+ }
+ }else{
+ if (MSG_get_clock() >= next_stabilize_date) {
+ stabilize(&node);
+ next_stabilize_date = MSG_get_clock() + periodic_stabilize_delay;
+ }
+ else if (MSG_get_clock() >= next_fix_fingers_date) {
+ fix_fingers(&node);
+ next_fix_fingers_date = MSG_get_clock() + periodic_fix_fingers_delay;
+ }
+ else if (MSG_get_clock() >= next_check_predecessor_date) {
+ check_predecessor(&node);
+ next_check_predecessor_date = MSG_get_clock() + periodic_check_predecessor_delay;
+ }
+ else if (MSG_get_clock() >= next_lookup_date) {
+ random_lookup(&node);
+ next_lookup_date = MSG_get_clock() + periodic_lookup_delay;
+ }
+ else {
+ // nothing to do: sleep for a while
+ MSG_process_sleep(5);
+ }
+ }
+ #else
+ if (MSG_get_clock() >= next_stabilize_date) {
+ stabilize(&node);
+ next_stabilize_date = MSG_get_clock() + periodic_stabilize_delay;
+ }
+ else if (MSG_get_clock() >= next_fix_fingers_date) {
+ fix_fingers(&node);
+ next_fix_fingers_date = MSG_get_clock() + periodic_fix_fingers_delay;
+ }
+ else if (MSG_get_clock() >= next_check_predecessor_date) {
+ check_predecessor(&node);
+ next_check_predecessor_date = MSG_get_clock() + periodic_check_predecessor_delay;
+ }
+ else if (MSG_get_clock() >= next_lookup_date) {
+ random_lookup(&node);
+ next_lookup_date = MSG_get_clock() + periodic_lookup_delay;
+ }
+ else {
+ // nothing to do: sleep for a while
+ MSG_process_sleep(5);
+ }
+ #endif
+
+ }else{
+
+ if (node.comm_receive) {
+
+ node_deliver = 0;
+
+ XBT_INFO("A transfer has occured");
+
+ // a transfer has occured
+
+ msg_error_t status = MSG_comm_get_status(node.comm_receive);
+
+ if (status != MSG_OK) {
+ XBT_INFO("Failed to receive a task. Nevermind.");
+ MSG_comm_destroy(node.comm_receive);
+ node.comm_receive = NULL;
+ }
+ else {
+ // the task was successfully received
+ XBT_INFO("The task was successfully received by node %d", node.id);
+ MSG_comm_destroy(node.comm_receive);
+ node.comm_receive = NULL;
+ handle_task(&node, task_received);
+ }
+ }
+ }
+ }
+
+ if (node.comm_receive) {
+ MSG_comm_destroy(node.comm_receive);
+ node.comm_receive = NULL;
+ }
+
+ // leave the ring
+ leave(&node);
+ }
+
+ // stop the simulation
+ xbt_free(node.fingers);
+ return 0;
+}
+
+/**
+ * \brief This function is called when the current node receives a task.
+ * \param node the current node
+ * \param task the task to handle (don't touch it then:
+ * it will be destroyed, reused or forwarded)
+ */
+static void handle_task(node_t node, msg_task_t task) {
+
+ XBT_DEBUG("Handling task %p", task);
+ char mailbox[MAILBOX_NAME_SIZE];
+ task_data_t task_data = (task_data_t) MSG_task_get_data(task);
+ e_task_type_t type = task_data->type;
+
+ switch (type) {
+
+ case TASK_FIND_SUCCESSOR:
+ node_deliver = 1;
+ XBT_DEBUG("Receiving a 'Find Successor' request from %s for id %d",
+ task_data->issuer_host_name, task_data->request_id);
+ // is my successor the successor?
+ if (is_in_interval(task_data->request_id, node->id + 1, node->fingers[0].id)) {
+ task_data->type = TASK_FIND_SUCCESSOR_ANSWER;
+ task_data->answer_id = node->fingers[0].id;
+ XBT_DEBUG("Sending back a 'Find Successor Answer' to %s (mailbox %s): the successor of %d is %d",
+ task_data->issuer_host_name,
+ task_data->answer_to,
+ task_data->request_id, task_data->answer_id);
+ MSG_task_dsend(task, task_data->answer_to, task_free);
+ }
+ else {
+ // otherwise, forward the request to the closest preceding finger in my table
+ int closest = closest_preceding_node(node, task_data->request_id);
+ XBT_DEBUG("Forwarding the 'Find Successor' request for id %d to my closest preceding finger %d",
+ task_data->request_id, closest);
+ get_mailbox(closest, mailbox);
+ MSG_task_dsend(task, mailbox, task_free);
+ }
+ break;
+
+ case TASK_GET_PREDECESSOR:
+ XBT_DEBUG("Receiving a 'Get Predecessor' request from %s", task_data->issuer_host_name);
+ task_data->type = TASK_GET_PREDECESSOR_ANSWER;
+ task_data->answer_id = node->pred_id;
+ XBT_DEBUG("Sending back a 'Get Predecessor Answer' to %s via mailbox '%s': my predecessor is %d",
+ task_data->issuer_host_name,
+ task_data->answer_to, task_data->answer_id);
+ MSG_task_dsend(task, task_data->answer_to, task_free);
+ break;
+
+ case TASK_NOTIFY:
+ // someone is telling me that he may be my new predecessor
+ XBT_DEBUG("Receiving a 'Notify' request from %s", task_data->issuer_host_name);
+ notify(node, task_data->request_id);
+ task_free(task);
+ break;
+
+ case TASK_PREDECESSOR_LEAVING:
+ // my predecessor is about to quit
+ XBT_DEBUG("Receiving a 'Predecessor Leaving' message from %s", task_data->issuer_host_name);
+ // modify my predecessor
+ set_predecessor(node, task_data->request_id);
+ task_free(task);
+ /*TODO :
+ >> notify my new predecessor
+ >> send a notify_predecessors !!
+ */
+ break;
+
+ case TASK_SUCCESSOR_LEAVING:
+ // my successor is about to quit
+ XBT_DEBUG("Receiving a 'Successor Leaving' message from %s", task_data->issuer_host_name);
+ // modify my successor FIXME : this should be implicit ?
+ set_finger(node, 0, task_data->request_id);
+ task_free(task);
+ /* TODO
+ >> notify my new successor
+ >> update my table & predecessors table */
+ break;
+
+ case TASK_FIND_SUCCESSOR_ANSWER:
+ case TASK_GET_PREDECESSOR_ANSWER:
+ XBT_DEBUG("Ignoring unexpected task of type %d (%p)", (int)type, task);
+ task_free(task);
+ break;
+ }
+}
+
+/**
+ * \brief Initializes the current node as the first one of the system.
+ * \param node the current node
+ */
+static void create(node_t node)
+{
+ XBT_DEBUG("Create a new Chord ring...");
+ set_predecessor(node, -1); // -1 means that I have no predecessor
+ print_finger_table(node);
+}
+
+/**
+ * \brief Makes the current node join the ring, knowing the id of a node
+ * already in the ring
+ * \param node the current node
+ * \param known_id id of a node already in the ring
+ * \return 1 if the join operation succeeded, 0 otherwise
+ */
+static int join(node_t node, int known_id)
+{
+ XBT_INFO("Joining the ring with id %d, knowing node %d", node->id, known_id);
+ set_predecessor(node, -1); // no predecessor (yet)
+
+ /*
+ int i;
+ for (i = 0; i < nb_bits; i++) {
+ set_finger(node, i, known_id);
+ }
+ */
+
+ int successor_id = remote_find_successor(node, known_id, node->id);
+ if (successor_id == -1) {
+ XBT_INFO("Cannot join the ring.");
+ }
+ else {
+ set_finger(node, 0, successor_id);
+ print_finger_table(node);
+ }
+
+ return successor_id != -1;
+}
+
+/**
+ * \brief Makes the current node quit the system
+ * \param node the current node
+ */
+static void leave(node_t node)
+{
+ XBT_DEBUG("Well Guys! I Think it's time for me to quit ;)");
+ quit_notify(node);
+}
+
+/*
+ * \brief Notifies the successor and the predecessor of the current node
+ * of the departure
+ * \param node the current node
+ */
+static void quit_notify(node_t node)
+{
+ char mailbox[MAILBOX_NAME_SIZE];
+ //send the PREDECESSOR_LEAVING to our successor
+ task_data_t req_data = xbt_new0(s_task_data_t,1);
+ req_data->type = TASK_PREDECESSOR_LEAVING;
+ req_data->request_id = node->pred_id;
+ get_mailbox(node->id, req_data->answer_to);
+ req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
+
+ msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
+ XBT_DEBUG("Sending a 'PREDECESSOR_LEAVING' to my successor %d",node->fingers[0].id);
+ MSG_task_send_with_timeout(task_sent, node->fingers[0].mailbox, timeout);
+
+ //send the SUCCESSOR_LEAVING to our predecessor
+ get_mailbox(node->pred_id, mailbox);
+ task_data_t req_data_s = xbt_new0(s_task_data_t,1);
+ req_data_s->type = TASK_SUCCESSOR_LEAVING;
+ req_data_s->request_id = node->fingers[0].id;
+ req_data_s->request_id = node->pred_id;
+ get_mailbox(node->id, req_data_s->answer_to);
+ req_data_s->issuer_host_name = MSG_host_get_name(MSG_host_self());
+
+ msg_task_t task_sent_s = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data_s);
+ XBT_DEBUG("Sending a 'SUCCESSOR_LEAVING' to my predecessor %d",node->pred_id);
+ MSG_task_send_with_timeout(task_sent_s, mailbox, timeout);
+
+}
+
+/**
+ * \brief Makes the current node find the successor node of an id.
+ * \param node the current node
+ * \param id the id to find
+ * \return the id of the successor node, or -1 if the request failed
+ */
+static int find_successor(node_t node, int id)
+{
+ // is my successor the successor?
+ if (is_in_interval(id, node->id + 1, node->fingers[0].id)) {
+ return node->fingers[0].id;
+ }
+
+ // otherwise, ask the closest preceding finger in my table
+ int closest = closest_preceding_node(node, id);
+ return remote_find_successor(node, closest, id);
+}
+
+/**
+ * \brief Asks another node the successor node of an id.
+ * \param node the current node
+ * \param ask_to the node to ask to
+ * \param id the id to find
+ * \return the id of the successor node, or -1 if the request failed
+ */
+static int remote_find_successor(node_t node, int ask_to, int id)
+{
+ int successor = -1;
+ int stop = 0;
+ char mailbox[MAILBOX_NAME_SIZE];
+ get_mailbox(ask_to, mailbox);
+ task_data_t req_data = xbt_new0(s_task_data_t, 1);
+ req_data->type = TASK_FIND_SUCCESSOR;
+ req_data->request_id = id;
+ get_mailbox(node->id, req_data->answer_to);
+ req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
+
+ // send a "Find Successor" request to ask_to_id
+ msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
+ XBT_DEBUG("Sending a 'Find Successor' request (task %p) to %d for id %d", task_sent, ask_to, id);
+ msg_error_t res = MSG_task_send_with_timeout(task_sent, mailbox, timeout);
+
+ if (res != MSG_OK) {
+ XBT_DEBUG("Failed to send the 'Find Successor' request (task %p) to %d for id %d",
+ task_sent, ask_to, id);
+ task_free(task_sent);
+ }
+ else {
+
+ // receive the answer
+ XBT_DEBUG("Sent a 'Find Successor' request (task %p) to %d for key %d, waiting for the answer",
+ task_sent, ask_to, id);
+
+ do {
+ if (node->comm_receive == NULL) {
+ msg_task_t task_received = NULL;
+ node->comm_receive = MSG_task_irecv(&task_received, node->mailbox);
+ }
+
+ res = MSG_comm_wait(node->comm_receive, timeout);
+
+ if (res != MSG_OK) {
+ XBT_DEBUG("Failed to receive the answer to my 'Find Successor' request (task %p): %d",
+ task_sent, (int)res);
+ stop = 1;
+ MSG_comm_destroy(node->comm_receive);
+ node->comm_receive = NULL;
+ }
+ else {
+ msg_task_t task_received = MSG_comm_get_task(node->comm_receive);
+ XBT_DEBUG("Received a task (%p)", task_received);
+ task_data_t ans_data = MSG_task_get_data(task_received);
+
+ if (MC_is_active()) {
+ // the model-checker is expected to find a counter-example here.
+ //
+ // As you can see in the test right below, task_received is not always equal to task_sent
+ // (as messages from differing round can interleave). But the previous version of this code
+ // wrongly assumed that, leading to problems. But this only occured on large platforms,
+ // leading to hardly usable traces. So we used the model-checker to track down the issue,
+ // and we came down to this test, that explained the bug in a snap.
+ //MC_assert(task_received == task_sent);
+ }
+
+ if (task_received != task_sent) {
+ // this is not the expected answer
+ MSG_comm_destroy(node->comm_receive);
+ node->comm_receive = NULL;
+ handle_task(node, task_received);
+ }
+ else {
+ // this is our answer
+ XBT_DEBUG("Received the answer to my 'Find Successor' request for id %d (task %p): the successor of key %d is %d",
+ ans_data->request_id, task_received, id, ans_data->answer_id);
+ successor = ans_data->answer_id;
+ stop = 1;
+ MSG_comm_destroy(node->comm_receive);
+ node->comm_receive = NULL;
+ task_free(task_received);
+ }
+ }
+ } while (!stop);
+ }
+
+ return successor;
+}
+
+/**
+ * \brief Asks another node its predecessor.
+ * \param node the current node
+ * \param ask_to the node to ask to
+ * \return the id of its predecessor node, or -1 if the request failed
+ * (or if the node does not know its predecessor)
+ */
+static int remote_get_predecessor(node_t node, int ask_to)
+{
+ int predecessor_id = -1;
+ int stop = 0;
+ char mailbox[MAILBOX_NAME_SIZE];
+ get_mailbox(ask_to, mailbox);
+ task_data_t req_data = xbt_new0(s_task_data_t, 1);
+ req_data->type = TASK_GET_PREDECESSOR;
+ get_mailbox(node->id, req_data->answer_to);
+ req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
+
+ // send a "Get Predecessor" request to ask_to_id
+ XBT_DEBUG("Sending a 'Get Predecessor' request to %d", ask_to);
+ msg_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
+ msg_error_t res = MSG_task_send_with_timeout(task_sent, mailbox, timeout);
+
+ if (res != MSG_OK) {
+ XBT_DEBUG("Failed to send the 'Get Predecessor' request (task %p) to %d",
+ task_sent, ask_to);
+ task_free(task_sent);
+ }
+ else {
+
+ // receive the answer
+ XBT_DEBUG("Sent 'Get Predecessor' request (task %p) to %d, waiting for the answer on my mailbox '%s'",
+ task_sent, ask_to, req_data->answer_to);
+
+ do {
+ if (node->comm_receive == NULL) { // FIXME simplify this
+ msg_task_t task_received = NULL;
+ node->comm_receive = MSG_task_irecv(&task_received, node->mailbox);
+ }
+
+ res = MSG_comm_wait(node->comm_receive, timeout);
+
+ if (res != MSG_OK) {
+ XBT_DEBUG("Failed to receive the answer to my 'Get Predecessor' request (task %p): %d",
+ task_sent, (int)res);
+ stop = 1;
+ MSG_comm_destroy(node->comm_receive);
+ node->comm_receive = NULL;
+ }
+ else {
+ msg_task_t task_received = MSG_comm_get_task(node->comm_receive);
+ task_data_t ans_data = MSG_task_get_data(task_received);
+
+ /*if (MC_is_active()) {
+ MC_assert(task_received == task_sent);
+ }*/
+
+ if (task_received != task_sent) {
+ MSG_comm_destroy(node->comm_receive);
+ node->comm_receive = NULL;
+ handle_task(node, task_received);
+ }
+ else {
+ XBT_DEBUG("Received the answer to my 'Get Predecessor' request (task %p): the predecessor of node %d is %d",
+ task_received, ask_to, ans_data->answer_id);
+ predecessor_id = ans_data->answer_id;
+ stop = 1;
+ MSG_comm_destroy(node->comm_receive);
+ node->comm_receive = NULL;
+ task_free(task_received);
+ }
+ }
+ } while (!stop);
+ }
+
+ return predecessor_id;
+}
+
+/**
+ * \brief Returns the closest preceding finger of an id
+ * with respect to the finger table of the current node.
+ * \param node the current node
+ * \param id the id to find
+ * \return the closest preceding finger of that id
+ */
+int closest_preceding_node(node_t node, int id)
+{
+ int i;
+ for (i = nb_bits - 1; i >= 0; i--) {
+ if (is_in_interval(node->fingers[i].id, node->id + 1, id - 1)) {
+ return node->fingers[i].id;
+ }
+ }
+ return node->id;
+}
+
+/**
+ * \brief This function is called periodically. It checks the immediate
+ * successor of the current node.
+ * \param node the current node
+ */
+static void stabilize(node_t node)
+{
+ XBT_DEBUG("Stabilizing node %d", node->id);
+
+ // get the predecessor of my immediate successor
+ int candidate_id;
+ int successor_id = node->fingers[0].id;
+ if (successor_id != node->id) {
+ candidate_id = remote_get_predecessor(node, successor_id);
+ }
+ else {
+ candidate_id = node->pred_id;
+ }
+
+ // this node is a candidate to become my new successor
+ if (candidate_id != -1
+ && is_in_interval(candidate_id, node->id + 1, successor_id - 1)) {
+ set_finger(node, 0, candidate_id);
+ }
+ if (successor_id != node->id) {
+ remote_notify(node, successor_id, node->id);
+ }
+}
+
+/**
+ * \brief Notifies the current node that its predecessor may have changed.
+ * \param node the current node
+ * \param candidate_id the possible new predecessor
+ */
+static void notify(node_t node, int predecessor_candidate_id) {
+
+ XBT_DEBUG("Notifying node %d", node->id);
+
+ if (node->pred_id == -1
+ || is_in_interval(predecessor_candidate_id, node->pred_id + 1, node->id - 1)) {
+
+ set_predecessor(node, predecessor_candidate_id);
+ print_finger_table(node);
+ }
+ else {
+ XBT_DEBUG("I don't have to change my predecessor to %d", predecessor_candidate_id);
+ }
+}
+
+/**
+ * \brief Notifies a remote node that its predecessor may have changed.
+ * \param node the current node
+ * \param notify_id id of the node to notify
+ * \param candidate_id the possible new predecessor
+ */
+static void remote_notify(node_t node, int notify_id, int predecessor_candidate_id) {
+
+ task_data_t req_data = xbt_new0(s_task_data_t, 1);
+ req_data->type = TASK_NOTIFY;
+ req_data->request_id = predecessor_candidate_id;
+ req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
+
+ // send a "Notify" request to notify_id
+ msg_task_t task = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
+ XBT_DEBUG("Sending a 'Notify' request (task %p) to %d", task, notify_id);
+ char mailbox[MAILBOX_NAME_SIZE];
+ get_mailbox(notify_id, mailbox);
+ MSG_task_dsend(task, mailbox, task_free);
+ }
+
+/**
+ * \brief This function is called periodically.
+ * It refreshes the finger table of the current node.
+ * \param node the current node
+ */
+static void fix_fingers(node_t node) {
+
+ XBT_DEBUG("Fixing fingers");
+ int i = node->next_finger_to_fix;
+ int id = find_successor(node, node->id + powers2[i]);
+ if (id != -1) {
+
+ if (id != node->fingers[i].id) {
+ set_finger(node, i, id);
+ print_finger_table(node);
+ }
+ node->next_finger_to_fix = (i + 1) % nb_bits;
+ }
+}
+
+/**
+ * \brief This function is called periodically.
+ * It checks whether the predecessor has failed
+ * \param node the current node
+ */
+static void check_predecessor(node_t node)
+{
+ XBT_DEBUG("Checking whether my predecessor is alive");
+ // TODO
+}
+
+/**
+ * \brief Performs a find successor request to a random id.
+ * \param node the current node
+ */
+static void random_lookup(node_t node)
+{
+ int id = 1337; // TODO pick a pseudorandom id
+ XBT_DEBUG("Making a lookup request for id %d", id);
+ find_successor(node, id);
+}
+
+static int predJoin(void){
+ return node_join;
+}
+
+static int predDeliver(void){
+ return node_deliver;
+}
+
+
+/**
+ * \brief Main function.
+ */
+int main(int argc, char *argv[])
+{
+ MSG_init(&argc, argv);
+ if (argc < 3) {
+ printf("Usage: %s [-nb_bits=n] [-timeout=t] platform_file deployment_file\n", argv[0]);
+ printf("example: %s ../../msg_platform.xml deploy_chord_liveness.xml\n", argv[0]);
+ exit(1);
+ }
+
+ char **options = &argv[1];
+ while (!strncmp(options[0], "-", 1)) {
+
+ int length = strlen("-nb_bits=");
+ if (!strncmp(options[0], "-nb_bits=", length) && strlen(options[0]) > length) {
+ nb_bits = atoi(options[0] + length);
+ XBT_DEBUG("Set nb_bits to %d", nb_bits);
+ }
+ else {
+
+ length = strlen("-timeout=");
+ if (!strncmp(options[0], "-timeout=", length) && strlen(options[0]) > length) {
+ timeout = atoi(options[0] + length);
+ XBT_DEBUG("Set timeout to %d", timeout);
+ }
+ else {
+ xbt_die("Invalid chord option '%s'", options[0]);
+ }
+ }
+ options++;
+ }
+
+ const char* platform_file = options[0];
+ const char* application_file = options[1];
+
+ chord_initialize();
+
+ MC_automaton_new_propositional_symbol("join", &predJoin);
+ MC_automaton_new_propositional_symbol("deliver", &predDeliver);
+
+ MSG_create_environment(platform_file);
+
+ MSG_function_register("node", node);
+ MSG_launch_application(application_file);
+
+ msg_error_t res = MSG_main();
+ XBT_INFO("Simulated time: %g", MSG_get_clock());
+
+ chord_exit();
+
+ if (res == MSG_OK)
+ return 0;
+ else
+ return 1;
+}
