1 /* Copyright (c) 2010, 2012-2018. The SimGrid Team.
2 * All rights reserved. */
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. */
8 #include "routing_table.hpp"
10 XBT_LOG_NEW_DEFAULT_CATEGORY(kademlia_node, "Messages specific for this example");
13 static void destroy(void* message)
15 Message* msg = static_cast<Message*>(message);
21 * @brief Tries to join the network
22 * @param known_id id of the node I know in the network.
24 bool Node::join(unsigned int known_id)
28 bool got_answer = false;
30 /* Add the guy we know to our routing table and ourselves. */
31 routingTableUpdate(id_);
32 routingTableUpdate(known_id);
34 /* First step: Send a "FIND_NODE" request to the node we know */
35 sendFindNode(known_id, id_);
37 simgrid::s4u::MailboxPtr mailbox = simgrid::s4u::Mailbox::byName(std::to_string(id_));
39 if (receive_comm == nullptr)
40 receive_comm = mailbox->get_async(&received_msg);
41 if (receive_comm->test()) {
42 XBT_DEBUG("Received an answer from the node I know.");
44 // retrieve the node list and ping them.
45 Message* msg = static_cast<Message*>(received_msg);
46 node_list = msg->answer_;
48 for (auto contact : node_list->nodes)
49 routingTableUpdate(contact.first);
55 receive_comm = nullptr;
57 simgrid::s4u::this_actor::sleep_for(1);
58 } while (not got_answer);
60 /* Second step: Send a FIND_NODE to a a random node in buckets */
61 unsigned int bucket_id = table->findBucket(known_id)->getId();
62 xbt_assert(bucket_id <= identifier_size);
63 for (i = 0; ((bucket_id > i) || (bucket_id + i) <= identifier_size) && i < JOIN_BUCKETS_QUERIES; i++) {
65 unsigned int id_in_bucket = get_id_in_prefix(id_, bucket_id - i);
66 findNode(id_in_bucket, false);
68 if (bucket_id + i <= identifier_size) {
69 unsigned int id_in_bucket = get_id_in_prefix(id_, bucket_id + i);
70 findNode(id_in_bucket, false);
76 /** @brief Send a "FIND_NODE" to a node
77 * @param id node we are querying
78 * @param destination node we are trying to find.
80 void Node::sendFindNode(unsigned int id, unsigned int destination)
82 /* Gets the mailbox to send to */
83 simgrid::s4u::MailboxPtr mailbox = simgrid::s4u::Mailbox::byName(std::to_string(id));
85 Message* msg = new Message(id_, destination, simgrid::s4u::Mailbox::byName(std::to_string(id_)),
86 simgrid::s4u::Host::current()->getCname());
89 mailbox->put_init(msg, 1)->detach(kademlia::destroy);
90 XBT_VERB("Asking %u for its closest nodes", id);
94 * Sends to the best "kademlia_alpha" nodes in the "node_list" array a "FIND_NODE" request, to ask them for their best
97 unsigned int Node::sendFindNodeToBest(Answer* node_list)
101 unsigned int destination = node_list->getDestinationId();
102 for (auto node_to_query : node_list->nodes) {
103 /* We need to have at most "kademlia_alpha" requests each time, according to the protocol */
104 /* Gets the node we want to send the query to */
105 if (node_to_query.first != id_) { /* No need to query ourselves */
106 sendFindNode(node_to_query.first, destination);
110 if (j == kademlia_alpha)
116 /** @brief Updates/Puts the node id unsigned into our routing table
117 * @param id The id of the node we need to add unsigned into our routing table
119 void Node::routingTableUpdate(unsigned int id)
121 // retrieval of the bucket in which the should be
122 Bucket* bucket = table->findBucket(id);
124 // check if the id is already in the bucket.
125 auto id_pos = std::find(bucket->nodes.begin(), bucket->nodes.end(), id);
127 if (id_pos == bucket->nodes.end()) {
128 /* We check if the bucket is full or not. If it is, we evict an old element */
129 if (bucket->nodes.size() >= BUCKET_SIZE) {
130 bucket->nodes.pop_back();
132 bucket->nodes.push_front(id);
133 XBT_VERB("I'm adding to my routing table %08x", id);
135 // We push the element to the front
136 bucket->nodes.erase(id_pos);
137 bucket->nodes.push_front(id);
138 XBT_VERB("I'm updating %08x", id);
142 /** @brief Finds the closest nodes to the node given.
143 * @param node : our node
144 * @param destination_id : the id of the guy we are trying to find
146 Answer* Node::findClosest(unsigned int destination_id)
148 Answer* answer = new Answer(destination_id);
149 /* We find the corresponding bucket for the id */
150 Bucket* bucket = table->findBucket(destination_id);
151 int bucket_id = bucket->getId();
152 xbt_assert((bucket_id <= identifier_size), "Bucket found has a wrong identifier");
153 /* So, we copy the contents of the bucket unsigned into our answer */
154 answer->addBucket(bucket);
156 /* However, if we don't have enough elements in our bucket, we NEED to include at least "bucket_size" elements
157 * (if, of course, we know at least "bucket_size" elements. So we're going to look unsigned into the other buckets.
159 for (int i = 1; answer->getSize() < BUCKET_SIZE && ((bucket_id - i > 0) || (bucket_id + i < identifier_size)); i++) {
160 /* We check the previous buckets */
161 if (bucket_id - i >= 0) {
162 Bucket* bucket_p = table->buckets[bucket_id - i];
163 answer->addBucket(bucket_p);
165 /* We check the next buckets */
166 if (bucket_id + i <= identifier_size) {
167 Bucket* bucket_n = table->buckets[bucket_id + i];
168 answer->addBucket(bucket_n);
171 /* We trim the array to have only bucket_size or less elements */
172 std::sort(answer->nodes.begin(), answer->nodes.end(), sortbydistance);
178 /** @brief Send a request to find a node in the node routing table.
179 * @param id_to_find the id of the node we are trying to find
181 bool Node::findNode(unsigned int id_to_find, bool count_in_stats)
183 unsigned int queries;
184 unsigned int answers;
185 bool destination_found = false;
186 unsigned int nodes_added = 0;
187 double global_timeout = simgrid::s4u::Engine::getClock() + find_node_global_timeout;
188 unsigned int steps = 0;
190 /* First we build a list of who we already know */
191 Answer* node_list = findClosest(id_to_find);
192 xbt_assert((node_list != nullptr), "node_list incorrect");
193 XBT_DEBUG("Doing a FIND_NODE on %08x", id_to_find);
195 /* Ask the nodes on our list if they have information about the node we are trying to find */
198 queries = sendFindNodeToBest(node_list);
200 double timeout = simgrid::s4u::Engine::getClock() + find_node_timeout;
202 double time_beginreceive = simgrid::s4u::Engine::getClock();
204 simgrid::s4u::MailboxPtr mailbox = simgrid::s4u::Mailbox::byName(std::to_string(id_));
206 if (receive_comm == nullptr)
207 receive_comm = mailbox->get_async(&received_msg);
209 if (receive_comm->test()) {
210 Message* msg = static_cast<Message*>(received_msg);
211 // Check if what we have received is what we are looking for.
212 if (msg->answer_ && msg->answer_->getDestinationId() == id_to_find) {
213 routingTableUpdate(msg->sender_id_);
215 for (auto contact : node_list->nodes)
216 routingTableUpdate(contact.first);
219 nodes_added = node_list->merge(msg->answer_);
220 XBT_DEBUG("Received an answer from %s (%s) with %zu nodes on it", msg->answer_to_->getCname(),
221 msg->issuer_host_name_, msg->answer_->nodes.size());
224 routingTableUpdate(msg->sender_id_);
225 XBT_DEBUG("Received a wrong answer for a FIND_NODE");
229 // Update the timeout if we didn't have our answer
230 timeout += simgrid::s4u::Engine::getClock() - time_beginreceive;
231 time_beginreceive = simgrid::s4u::Engine::getClock();
235 receive_comm = nullptr;
237 simgrid::s4u::this_actor::sleep_for(1);
239 } while (simgrid::s4u::Engine::getClock() < timeout && answers < queries);
240 destination_found = node_list->destinationFound();
241 } while (not destination_found && (nodes_added > 0 || answers == 0) &&
242 simgrid::s4u::Engine::getClock() < global_timeout && steps < MAX_STEPS);
244 if (destination_found) {
248 XBT_VERB("FIND_NODE on %08x success in %u steps", id_to_find, steps);
249 routingTableUpdate(id_to_find);
251 if (count_in_stats) {
253 XBT_VERB("%08x not found in %u steps", id_to_find, steps);
257 return destination_found;
260 /** @brief Does a pseudo-random lookup for someone in the system
261 * @param node caller node data
263 void Node::randomLookup()
265 unsigned int id_to_look = RANDOM_LOOKUP_NODE; // Totally random.
266 /* TODO: Use some pseudo-random generator like RngStream. */
267 XBT_DEBUG("I'm doing a random lookup");
268 findNode(id_to_look, true);
271 /** @brief Handles the answer to an incoming "find_node" task */
272 void Node::handleFindNode(Message* msg)
274 routingTableUpdate(msg->sender_id_);
275 XBT_VERB("Received a FIND_NODE from %s (%s), he's trying to find %08x", msg->answer_to_->getCname(),
276 msg->issuer_host_name_, msg->destination_id_);
277 // Building the answer to the request
279 new Message(id_, msg->destination_id_, findClosest(msg->destination_id_),
280 simgrid::s4u::Mailbox::byName(std::to_string(id_)), simgrid::s4u::Host::current()->getCname());
281 // Sending the answer
282 msg->answer_to_->put_init(answer, 1)->detach(kademlia::destroy);
285 /**@brief Returns an identifier which is in a specific bucket of a routing table
286 * @param id id of the routing table owner
287 * @param prefix id of the bucket where we want that identifier to be
289 unsigned int get_id_in_prefix(unsigned int id, unsigned int prefix)
294 return (1U << ((unsigned int)(prefix - 1))) ^ id;
298 /** @brief Returns the prefix of an identifier.
299 * The prefix is the id of the bucket in which the remote identifier xor our identifier should be stored.
300 * @param id : big unsigned int id to test
301 * @param nb_bits : key size
303 unsigned int get_node_prefix(unsigned int id, unsigned int nb_bits)
305 unsigned int size = sizeof(unsigned int) * 8;
306 for (unsigned int j = 0; j < size; j++) {
307 if (((id >> (size - 1 - j)) & 0x1) != 0) {
308 return nb_bits - (j);