source: source/ariba/overlay/modules/chord/Chord.cpp@ 5872

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// [License]

#include "ariba/overlay/BaseOverlay.h"
#include "ariba/overlay/messages/OverlayMsg.h"

#include "Chord.h"
#include "detail/chord_routing_table.hpp"

#include "messages/Discovery.h"

namespace ariba {
namespace overlay {

enum signalMessageTypes {
        typeDiscovery = OverlayMsg::typeSignalingStart + 0x01,
        typeLeave = OverlayMsg::typeSignalingStart + 0x02,
};

typedef chord_routing_table::item route_item;

use_logging_cpp( Chord );

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

        // create routing table
        this->table = new chord_routing_table(_nodeid, 4);
        orphan_removal_counter = 0;
        discovery_count = 0;
        stabilize_counter = 0;
        stabilize_finger = 0;
}

Chord::~Chord() {

        // delete routing table
        delete table;
}

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

        // check if we already have a connection
        for (int i=0; i<table->size(); i++)
                if ((*table)[i]->ref_count > 0 && (*table)[i]->id == remote && !((*table)[i]->info.isUnspecified()))
                        return LinkID::UNSPECIFIED;

        // check if we are already trying to establish a link
        for (size_t i=0; i<pending.size(); i++)
                if ( pending[i] == remote ) {
                        logging_debug("Already trying to establish a link to node "
                                << remote.toString() );
                        return LinkID::UNSPECIFIED;
                }

        // adding node to list of pending connections
        pending.push_back( remote );

        logging_info("Request to setup link to " << endpoint.toString() );

        // establish link via base overlay
        return baseoverlay.establishLink( endpoint, remote,
                        OverlayInterface::OVERLAY_SERVICE_ID );
}

/// helper: sends a message using the "base overlay"
seqnum_t Chord::send( OverlayMsg* msg, const LinkID& link ) {
        if (link.isUnspecified()) return 0;
        msg->setRelayed(true);
        return baseoverlay.send_link( msg, link );
}

/// sends a discovery message
void Chord::send_discovery_to(const NodeID& remote, int ttl) {
        LinkID link = getNextLinkId(remote);
        if ( remote == nodeid || link.isUnspecified()) return;
        if ( table->size() == 0 ) return;

        OverlayMsg msg( typeDiscovery );
        msg.setRelayed(true);
        Discovery dmsg( Discovery::normal, (uint8_t)2, baseoverlay.getEndpointDescriptor() );
        msg.encapsulate(&dmsg);

        // send to node
        baseoverlay.send_node( &msg, remote );
}

void Chord::discover_neighbors( const LinkID& link ) {
        uint8_t ttl = 2;
        {
                // send predecessor discovery
                OverlayMsg msg( typeDiscovery );
                msg.setRelayed(true);
                Discovery dmsg( Discovery::predecessor, ttl,
                        baseoverlay.getEndpointDescriptor() );
                msg.encapsulate(&dmsg);
                send(&msg, link);
        }
        {
                // send successor discovery
                OverlayMsg msg( typeDiscovery );
                msg.setSourceEndpoint( baseoverlay.getEndpointDescriptor() );
                msg.setRelayed(true);
                Discovery dmsg( Discovery::successor, ttl,
                        baseoverlay.getEndpointDescriptor() );
                msg.encapsulate(&dmsg);
                send(&msg, link);
        }
}


void Chord::createOverlay() {
}

void Chord::deleteOverlay() {

}

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

        // initiator? no->setup first link
        if (!boot.isUnspecified())
                bootstrapLinks.push_back( setup(boot) );

        // timer for stabilization management
        Timer::setInterval(1000);
        Timer::start();
}

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

/// @see OverlayInterface.h
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);
}

/// @see OverlayInterface.h
const LinkID& Chord::getNextLinkId( const NodeID& id ) const {
        // get next hop
        const route_item* item = table->get_next_hop(id);

        // returns a unspecified id when this is itself
        if (item == NULL || item->id == nodeid)
                return LinkID::UNSPECIFIED;

        /// return routing info
        return item->info;
}

OverlayInterface::NodeList Chord::getKnownNodes(bool deep) const {
        OverlayInterface::NodeList nodelist;

        if( deep ){
                // all nodes that I know, fingers, succ/pred
                for (size_t i = 0; i < table->size(); i++){
                        if ((*table)[i]->ref_count != 0
                                        && !(*table)[i]->info.isUnspecified())
                                nodelist.push_back((*table)[i]->id);
                }
        } else {
                // only succ and pred
                if( table->get_predesessor() != NULL ){
                        nodelist.push_back( *(table->get_predesessor()) );
                }
                if( table->get_successor() != NULL ){
                        OverlayInterface::NodeList::iterator i =
                                std::find( nodelist.begin(), nodelist.end(), *(table->get_successor()) );
                        if( i == nodelist.end() )
                                nodelist.push_back( *(table->get_successor()) );
                }
        }

        return nodelist;
}

/// @see CommunicationListener.h
/// @see OverlayInterface.h
void Chord::onLinkUp(const LinkID& lnk, const NodeID& remote) {
        logging_info("link_up: link=" << lnk.toString() << " remote=" <<
                        remote.toString() );
        for (vector<NodeID>::iterator i=pending.begin(); i!=pending.end(); i++)
                if (*i == remote) {
                        pending.erase(i);
                        break;
                }
/*
        // check if we already have a connection, yes-> do not handle duplicate!
        for (int i=0; i<table->size(); i++)
                if ((*table)[i]->id == remote && !((*table)[i]->info.isUnspecified()) && (*table)[i]->info != lnk) {

                        return;
                }
*/
        if (remote==nodeid) {
                baseoverlay.dropLink(lnk);
                return;
        }

        route_item* item = table->insert(remote);

        // item added to routing table?
        if (item != NULL) { // yes-> add to routing table
                logging_info("new routing neighbor: " << remote.toString()
                                << " with link " << lnk.toString());
                // replace with new link
                if (!item->info.isUnspecified() || item->info!=lnk)
                        baseoverlay.dropLink(item->info);
                item->info = lnk;
                // discover neighbors of new overlay neighbor
                discover_neighbors( lnk );
                showLinks();
        } else { // no-> add orphan entry to routing table
                logging_info("new orphan: " << remote.toString()
                                << " with link " << lnk.toString());
                table->insert_orphan(remote)->info = lnk;
        }

        // erase bootstrap link
        vector<LinkID>::iterator it = std::find(bootstrapLinks.begin(), bootstrapLinks.end(), lnk);
        if( it != bootstrapLinks.end() ) bootstrapLinks.erase( it );
}

/// @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
        route_item* item = table->get(remote);
        if (item!=NULL && item->info==lnk) {
                item->info = LinkID::UNSPECIFIED;
                table->remove(remote);
        }
}

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

        // decode message
        OverlayMsg* m = dynamic_cast<OverlayMsg*>(msg.getMessage());
        if (m == NULL) return;

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

        // discovery request
        case typeDiscovery: {
                // decapsulate message
                Discovery* dmsg = m->decapsulate<Discovery> ();
                logging_debug("Received discovery message with"
                            << " src=" << m->getSourceNode().toString()
                                << " dst=" << m->getDestinationNode().toString()
                                << " ttl=" << (int)dmsg->getTTL()
                                << " type=" << (int)dmsg->getType()
                );

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

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

                // 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->getDestinationNode()) ) {

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

                                // send predecessor message
                                if (table->get_predesessor() != NULL) {
                                        OverlayMsg omsg(*m);
                                        dmsg->setType(Discovery::predecessor);
                                        omsg.encapsulate(dmsg);
                                        route_item* pred_item = table->get(
                                                        *table->get_predesessor());
                                        logging_debug("Discovery split: routing discovery message to predecessor "
                                                        << pred_item->id.toString() );
                                        send( &omsg, pred_item->info);
                                }
                        }
                        // no-> route message
                        else {
                                baseoverlay.send( m, m->getDestinationNode() );
                        }
                        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 || dmsg->getTTL() > 10) break;

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

                        const route_item* item = NULL;
                        if (dmsg->getType() == Discovery::successor &&
                                        table->get_successor() != NULL) {
                                item = table->get(*table->get_successor());
                        } else {
                                if (table->get_predesessor()!=NULL)
                                        item = table->get(*table->get_predesessor());
                        }
                        if (item == NULL) break;
                        logging_debug("routing discovery message to succ/pred "
                                << item->id.toString() );
                        OverlayMsg omsg(*m);
                        omsg.encapsulate(dmsg);
                        omsg.setDestinationNode(item->id);
                        baseoverlay.send(&omsg, omsg.getDestinationNode());
                        break;
                }}
                delete dmsg;
                break;
        }

        // leave
        case typeLeave: {
                if (link!=LinkID::UNSPECIFIED) {
                        route_item* item = table->get(remote);
                        if (item!=NULL) item->info = LinkID::UNSPECIFIED;
                        table->remove(remote);
                        baseoverlay.dropLink(link);
                }
                break;
        }}
}

void Chord::eventFunction() {
        stabilize_counter++;
        if (stabilize_counter < 0 || stabilize_counter == 4) {

                // reset counter
                stabilize_counter = 0;

                // clear pending connections
                pending.clear();

                // get number of real neighbors
                size_t numNeighbors = 0;
                for (size_t i = 0; i < table->size(); i++) {
                        route_item* it = (*table)[i];
                        if (it->ref_count != 0 && !it->info.isUnspecified()) numNeighbors++;
                }
                logging_info("Running stabilization: #links="
                                << table->size() << " #neighbors=" << numNeighbors );

                // sending discovery
                logging_debug("Sending discovery message to my neighbors and fingers");
                stabilize_finger = ((stabilize_finger+1) % table->get_finger_table_size() );
                const NodeID disc1 = nodeid;
                const NodeID disc2 = table->get_finger_table(stabilize_finger).get_compare().get_center();
                send_discovery_to(disc1);
                if (disc1 != disc2)
                        send_discovery_to(disc2);

                for (int i=0; i<table->size(); i++) {
                        LinkID id = (*table)[i]->info;
                        if (!id.isUnspecified()) discover_neighbors(id);
                }

                // remove orphan links
                orphan_removal_counter++;
                if (orphan_removal_counter <0 || orphan_removal_counter >= 2) {
                        logging_info("Running orphan removal");
                        orphan_removal_counter = 0;
                        for (size_t i = 0; i < table->size(); i++) {
                                route_item* it = (*table)[i];
                                if (it->ref_count == 0 && !it->info.isUnspecified()) {
                                        logging_info("Dropping orphaned link " << it->info.toString() << " to " << it->id.toString());
                                        table->insert(it->id);
                                        if (it->ref_count==0) {
                                                LinkID id = it->info;
                                                it->info = LinkID::UNSPECIFIED;
                                                baseoverlay.dropLink(id);
                                        }
                                }
                        }
                }
        }
}

void Chord::showLinks() {
        logging_info("--- chord routing information ----------------------------------");
        logging_info("predecessor: " << (table->get_predesessor()==NULL? "<none>" :
                table->get_predesessor()->toString()) );
        logging_info("node_id    : " << nodeid.toString() );
        logging_info("successor  : " << (table->get_successor()==NULL? "<none>" :
                table->get_successor()->toString()));
        logging_info("----------------------------------------------------------------");
}

}} // namespace ariba, overlay