source: source/ariba/overlay/modules/chord/Chord.cpp @ 3690

// [License]
// The Ariba-Underlay Copyright
//
// Copyright (c) 2008-2009, Institute of Telematics, UniversitÀt Karlsruhe (TH)
//
// Institute of Telematics
// UniversitÀt Karlsruhe (TH)
// Zirkel 2, 76128 Karlsruhe
// Germany
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE INSTITUTE OF TELEMATICS ``AS IS'' AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE ARIBA PROJECT OR
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// The views and conclusions contained in the software and documentation
// are those of the authors and should not be interpreted as representing
// official policies, either expressed or implied, of the Institute of
// Telematics.
// [License]

#include "ariba/overlay/BaseOverlay.h"

#include "Chord.h"
#include "messages/ChordMessage.h"
#include "messages/Discovery.h"

#include "detail/chord_routing_table.hpp"

namespace ariba {
namespace overlay {

typedef chord_routing_table::item route_item;
use_logging_cpp( Chord )
;

Chord::Chord(BaseOverlay& _baseoverlay, const NodeID& _nodeid,
                OverlayStructureEvents* _eventsReceiver) :
        OverlayInterface(_baseoverlay, _nodeid, _eventsReceiver) {

        // create routing table
        this->table = new chord_routing_table(_nodeid, 2);
        orphan_removal_counter = 0;
        stabilize_counter = 0;
        stabilize_finger = 0;
        bootstrapLink = LinkID::UNSPECIFIED;
}

Chord::~Chord() {

        // delete routing table
        delete table;
}

// helper: sets up a link using the base overlay
LinkID Chord::setup(const EndpointDescriptor& endp) {

        logging_debug("request to setup link to " << endp.toString() );
        // establish link via base overlay
        return baseoverlay.establishLink(endp, OverlayInterface::OVERLAY_SERVICE_ID);
}

// helper: sends a message using the "base overlay"
seqnum_t Chord::send(Message* msg, const LinkID& link) {
        return baseoverlay.sendMessage(msg, link);
}

void Chord::send_discovery_to(const NodeID& destination, int ttl) {
        logging_debug("Initiating discovery of " << destination.toString() );
        Message msg;
        ChordMessage cmsg(ChordMessage::discovery, nodeid, destination);
        Discovery dmsg;
        dmsg.setSourceEndpoint(&baseoverlay.getEndpointDescriptor());
        dmsg.setFollowType(Discovery::normal);
        dmsg.setTTL((uint8_t) ttl);
        cmsg.encapsulate(&dmsg);
        msg.encapsulate(&cmsg);
        logging_debug("" << (int)cmsg.getType());
        this->onMessage(&msg, NodeID::UNSPECIFIED, LinkID::UNSPECIFIED);
}

void Chord::createOverlay() {
}

void Chord::deleteOverlay() {

}

void Chord::joinOverlay(const EndpointDescriptor& boot) {
        logging_info( "joining Chord overlay structure through end-point " <<
                        (boot == EndpointDescriptor::UNSPECIFIED ?
                                        "local" : boot.toString()) );

        // initiator? no->setup first link
        if (!(boot == EndpointDescriptor::UNSPECIFIED)) bootstrapLink = setup(boot);

        // timer for stabilization management
        Timer::setInterval(2500);
        Timer::start();
}

void Chord::leaveOverlay() {
        Timer::stop();
        for (size_t i = 0; i < table->size(); i++) {
                route_item* it = (*table)[i];
                ChordMessage msg(ChordMessage::leave, nodeid, it->id);
                send(&msg,it->info);
        }
}

const EndpointDescriptor& Chord::resolveNode(const NodeID& node) {
        const route_item* item = table->get(node);
        if (item == NULL || item->info.isUnspecified()) return EndpointDescriptor::UNSPECIFIED;
        return baseoverlay.getEndpointDescriptor(item->info);
}

void Chord::routeMessage(const NodeID& destnode, Message* msg) {
        // get next hop
        const route_item* item = table->get_next_hop(destnode);

        // message for this node? yes-> delegate to base overlay
        if (item->id == nodeid) baseoverlay.incomingRouteMessage(msg);
        else { // no-> send to next hop
                ChordMessage cmsg(ChordMessage::route, nodeid, destnode);
                cmsg.encapsulate(msg);
                send(&cmsg, item->info);
        }
}

OverlayInterface::NodeList Chord::getKnownNodes() const {
        OverlayInterface::NodeList nodelist;
        for (size_t i = 0; i < table->size(); i++)
                if ((*table)[i]->ref_count != 0) nodelist.push_back((*table)[i]->id);
        return nodelist;
}

/// @see CommunicationListener.h
/// @see OverlayInterface.h
void Chord::onLinkUp(const LinkID& lnk, const NodeID& remote) {
        logging_debug("link_up: link=" << lnk.toString() << " remote=" <<
                        remote.toString() );
        route_item* item = table->insert(remote);

        if (!bootstrapLink.isUnspecified() && lnk == bootstrapLink) {
                send_discovery_to(nodeid);
                bootstrapLink = LinkID::UNSPECIFIED;
        }

        // item added to routing table?
        if (item != NULL) { // yes-> add to routing table
                logging_debug("new routing neighbor: " << remote.toString() );
                item->info = lnk;
        } else { // no-> add orphan entry to routing table
                logging_debug("new orphan: " << remote.toString() );
                table->insert_orphan(remote)->info = lnk;
        }
}

/// @see CommunicationListener.h or @see OverlayInterface.h
void Chord::onLinkDown(const LinkID& lnk, const NodeID& remote) {
        logging_debug("link_down: link=" << lnk.toString() << " remote=" <<
                        remote.toString() );

        // remove link from routing table
        table->remove(remote);
}

/// @see CommunicationListener.h
/// @see OverlayInterface.h
void Chord::onMessage(const DataMessage& msg, const NodeID& remote,
                const LinkID& link) {

        // decode message
        typedef ChordMessage M;
        M* m = msg.getMessage()->convert<ChordMessage> ();
        if (m == NULL) return;

        logging_debug("onMessage: type=" << (int)m->getType() );

        // handle messages
        switch (m->getType()) {

        // invalid message
        case M::invalid:
                break;

                // route message with payload
        case M::route: {
                // find next hop
                const route_item* item = table->get_next_hop(m->getDestination());

                // next hop == myself?
                if (m->getDestination() == nodeid) { // yes-> route to base overlay
                        logging_debug("send message to baseoverlay");
                        baseoverlay.incomingRouteMessage(m);
                }
                // no-> route to next hop
                else {
                        logging_debug("route chord message to " << item->id.toString() );
                        send(m, item->info);
                }
                break;
        }

                // discovery request
        case M::discovery: {
                // decapsulate message
                Discovery* dmsg = m->decapsulate<Discovery> ();
                logging_debug("received discovery message with"
                                << " dest=" << m->getDestination().toString()
                                << " ttl=" << (int)dmsg->getTTL()
                                << " type=" << (int)dmsg->getFollowType()
                );

                // check if source node can be added to routing table and setup link
                if (m->getSource() != nodeid && table->is_insertable(m->getSource())) setup(
                                *dmsg->getSourceEndpoint());

                // delegate discovery message
                switch (dmsg->getFollowType()) {

                // normal: route discovery message like every other message
                case Discovery::normal:
                        // closest node? yes-> split to follow successor and predecessor
                        if (table->is_closest_to(m->getDestination())) {

                                if (table->get_successor() != NULL) {
                                        // send successor message
                                        ChordMessage cmsg_s(*m);
                                        Discovery dmsg_s(*dmsg);
                                        dmsg_s.setFollowType(Discovery::successor);
                                        cmsg_s.encapsulate(&dmsg_s);
                                        route_item* succ_item = table->get(*table->get_successor());
                                        logging_debug("split: routing discovery message to successor "
                                                        << succ_item->id.toString() );
                                        send(&cmsg_s, succ_item->info);
                                }

                                // send predecessor message
                                if (table->get_predesessor() != NULL) {
                                        ChordMessage cmsg_p(*m);
                                        Discovery dmsg_p(*dmsg);
                                        dmsg_p.setFollowType(Discovery::predecessor);
                                        cmsg_p.encapsulate(&dmsg_p);
                                        route_item* pred_item = table->get(
                                                        *table->get_predesessor());
                                        logging_debug("split: routing discovery message to predecessor "
                                                        << pred_item->id.toString() );
                                        send(&cmsg_p, pred_item->info);
                                }
                        }
                        // no-> route message
                        else {
                                // find next hop
                                const route_item* item = table->get_next_hop(
                                                m->getDestination());
                                if (item->id == nodeid) break;
                                logging_debug("routing discovery message to " <<
                                                item->id.toString() );
                                send(m, item->info);
                        }
                        break;

                        // successor mode: follow the successor until TTL is zero
                case Discovery::successor:
                case Discovery::predecessor: {
                        // time to live ended? yes-> stop routing
                        if (dmsg->getTTL() == 0) break;

                        // decrease time-to-live
                        dmsg->setTTL(dmsg->getTTL() - 1);

                        const route_item* item;
                        if (dmsg->getFollowType() == Discovery::successor) item
                                        = table->get(*table->get_successor());
                        else item = table->get(*table->get_predesessor());
                        logging_debug("routing discovery message to succ/pred "
                                        << item->id.toString() );
                        ChordMessage cmsg(*m);
                        cmsg.encapsulate(dmsg);
                        send(&cmsg, item->info);
                        break;
                }
                }
                break;
        }

                // leave
        case M::leave: {
                baseoverlay.dropLink(link);
                break;
        }
        }
}

void Chord::eventFunction() {
        stabilize_counter++;
        if (stabilize_counter == 3) {
                stabilize_counter = 0;
                stabilize_finger = ((stabilize_finger+1) % table->get_finger_table_size() );
                logging_debug("sending discovery message to my neighbors");
                send_discovery_to(nodeid);
                send_discovery_to(
                        table->get_finger_table(stabilize_finger).get_compare().get_center()
                );
                orphan_removal_counter++;
                if (orphan_removal_counter == 2) {
                        orphan_removal_counter = 0;
                        for (size_t i = 0; i < table->size(); i++) {
                                route_item* it = (*table)[i];
                                if (it->ref_count == 0) {
                                        baseoverlay.dropLink(it->info);
                                        logging_debug("dropping orphaned link " << it->info.toString() << " to " << it->id.toString());
                                }
                        }
                }
        }
        logging_debug("--- chord routing information ----------------------------------");
        logging_debug("predecessor: " << (table->get_predesessor()==NULL? "<none>" : table->get_predesessor()->toString()) );
        logging_debug("node_id    : " << nodeid.toString() );
        logging_debug("successor  : " << (table->get_successor()==NULL? "<none>" : table->get_successor()->toString()));
        logging_debug("----------------------------------------------------------------");
}

}
} // namespace ariba, overlay