examples/c/app-bittorrent/tracker.c

   1 /* Copyright (c) 2012-2020. The SimGrid Team.
   2  * All rights reserved.                                                     */
   3
   4 /* This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the license (GNU LGPL) which comes with this package. */
   6
   7 #include "tracker.h"
   8
   9 #include "simgrid/actor.h"
  10 #include "simgrid/comm.h"
  11 #include "simgrid/engine.h"
  12 #include "xbt/log.h"
  13
  14 XBT_LOG_NEW_DEFAULT_CATEGORY(bittorrent_tracker, "Messages specific for the tracker");
  15
  16 void tracker_answer_free(void* data)
  17 {
  18   tracker_answer_t a = (tracker_answer_t)data;
  19   xbt_dynar_free(&a->peers);
  20   free(a);
  21 }
  22
  23 static int is_in_list(const_xbt_dynar_t peers, int id)
  24 {
  25   return xbt_dynar_member(peers, &id);
  26 }
  27
  28 void tracker(int argc, char* argv[])
  29 {
  30   // Checking arguments
  31   xbt_assert(argc == 2, "Wrong number of arguments for the tracker.");
  32   // Retrieving end time
  33   double deadline = xbt_str_parse_double(argv[1], "Invalid deadline: %s");
  34   xbt_assert(deadline > 0, "Wrong deadline supplied");
  35
  36   // Building peers array
  37   xbt_dynar_t peers_list = xbt_dynar_new(sizeof(int), NULL);
  38
  39   sg_mailbox_t mailbox = sg_mailbox_by_name(TRACKER_MAILBOX);
  40
  41   XBT_INFO("Tracker launched.");
  42   sg_comm_t comm_received = NULL;
  43   void* received          = NULL;
  44
  45   while (simgrid_get_clock() < deadline) {
  46     if (comm_received == NULL)
  47       comm_received = sg_mailbox_get_async(mailbox, &received);
  48
  49     if (sg_comm_test(comm_received)) {
  50       // Retrieve the data sent by the peer.
  51       xbt_assert(received != NULL);
  52       tracker_query_t tq = (tracker_query_t)received;
  53
  54       // Add the peer to our peer list.
  55       if (!is_in_list(peers_list, tq->peer_id))
  56         xbt_dynar_push_as(peers_list, int, tq->peer_id);
  57
  58       // Sending peers to the requesting peer
  59       tracker_answer_t ta = tracker_answer_new(TRACKER_QUERY_INTERVAL);
  60       int next_peer;
  61       int peers_length = (int)xbt_dynar_length(peers_list);
  62       for (int i = 0; i < MAXIMUM_PEERS && i < peers_length; i++) {
  63         do {
  64           next_peer = xbt_dynar_get_as(peers_list, rand() % peers_length, int);
  65         } while (is_in_list(ta->peers, next_peer));
  66         xbt_dynar_push_as(ta->peers, int, next_peer);
  67       }
  68       // sending the task back to the peer.
  69       sg_comm_t answer = sg_mailbox_put_init(tq->return_mailbox, ta, TRACKER_COMM_SIZE);
  70       sg_comm_detach(answer, tracker_answer_free);
  71
  72       xbt_free(tq);
  73       comm_received = NULL;
  74       received      = NULL;
  75     } else {
  76       sg_actor_sleep_for(1);
  77     }
  78   }
  79   // Free the remaining communication if any
  80   if (comm_received)
  81     sg_comm_unref(comm_received);
  82   // Free the peers list
  83   xbt_dynar_free(&peers_list);
  84
  85   XBT_INFO("Tracker is leaving");
  86 }
  87
  88 tracker_query_t tracker_query_new(int peer_id, sg_mailbox_t return_mailbox)
  89 {
  90   tracker_query_t tq = xbt_new(s_tracker_query_t, 1);
  91   tq->peer_id        = peer_id;
  92   tq->return_mailbox = return_mailbox;
  93   return tq;
  94 }
  95
  96 tracker_answer_t tracker_answer_new(int interval)
  97 {
  98   tracker_answer_t ta = xbt_new(s_tracker_answer_t, 1);
  99   ta->interval        = interval;
 100   ta->peers           = xbt_dynar_new(sizeof(int), NULL);
 101
 102   return ta;
 103 }