Changeset 12060 for source/ariba/overlay/modules

Timestamp:

Jun 19, 2013, 11:05:49 AM (12 years ago)

Author:

hock@…

Message:

Reintegrate branch: 20130111-hock-message_classes

improvements:

• new message classes (reboost, zero-copy)
• "fast path" for direct links (skip overlay layer)
• link-properties accessible from the application
• SystemQueue can call boost::bind functions
• protlib compatibility removed (32bit overhead saved in every message)
• addressing2
• AddressDiscovery discoveres only addresses on which we're actually listening
• ariba serialization usage reduced (sill used in OverlayMsg)
• Node::connect, easier and cleaner interface to start-up ariba from the application
• ariba configs via JSON, XML, etc (boost::property_tree)
• keep-alive overhead greatly reduced
• (relayed) overlay links can actually be closed now
• lost messages are detected in most cases
• notification to the application when link is transformed into direct-link
• overlay routing: send message to second best hop if it would be dropped otherwise
• SequenceNumbers (only mechanisms, so for: upward compatibility)
• various small fixes

regressions:

• bluetooth is not yet working again
• bootstrap modules deactivated
• liblog4xx is not working (use cout-logging)

This patch brings great performance and stability improvements at cost of backward compatibility.
Also bluetooth and the bootstrap modules have not been ported to the new interfaces, yet.

Location:

source/ariba/overlay/modules

Files:

• OverlayFactory.cpp (modified) (2 diffs)
• OverlayInterface.cpp (modified) (2 diffs)
• OverlayInterface.h (modified) (2 diffs)
• OverlayStructureEvents.h (modified) (2 diffs)
• chord/Chord.cpp (modified) (11 diffs)
• chord/Chord.h (modified) (4 diffs)
• chord/detail/chord_routing_table.hpp (modified) (3 diffs)
• chord/messages/CMakeLists.txt (modified) (1 diff)
• chord/messages/Discovery.h (modified) (1 diff)
• onehop/CMakeLists.txt (modified) (1 diff)

source/ariba/overlay/modules/OverlayFactory.cpp

@@ -41 +41 @@
 // structured overlays
 #include "chord/Chord.h"
-#include "onehop/OneHop.h"
+//#include "onehop/OneHop.h"  //DEPRECATED
 
 namespace ariba {
@@ -57 +57 @@
                         return new Chord( baseoverlay, nodeid, routeReceiver, param );
 
-                case OverlayParameterSet::OverlayStructureOneHop:
-                        return new OneHop( baseoverlay, nodeid, routeReceiver, param );
+//              case OverlayParameterSet::OverlayStructureOneHop:
+//                      return new OneHop( baseoverlay, nodeid, routeReceiver, param );
 
                 default:
+                    // NEVER return "NULL"
+                    assert(false);
+                    throw 42;
                         return NULL;
         }
 
+        // NEVER return "NULL"
+        assert(false);
+        throw 42;
         return NULL;
 }

source/ariba/overlay/modules/OverlayInterface.cpp

@@ -68 +68 @@
 
 void OverlayInterface::onLinkFail(const LinkID& lnk, const NodeID& remote) {
+    onLinkDown(lnk, remote);
 }
 
@@ -79 +80 @@
 }
 
-void OverlayInterface::onMessage(const DataMessage& msg, const NodeID& remote,
+void OverlayInterface::onMessage(OverlayMsg* msg,
+        reboost::shared_buffer_t sub_msg,
+        const NodeID& remote,
                 const LinkID& lnk) {
 }

source/ariba/overlay/modules/OverlayInterface.h

@@ -145 +145 @@
          */
         virtual const LinkID& getNextLinkId( const NodeID& id ) const = 0;
-        
+
+    /**
+     * Returns link ids of possible next hops a route message could take,
+     * sorted by "quality" (e.g. overlay-distance).
+     *
+     * The »num« parameter can be used to specify the desired number of elements 
+     * in the returned vector. This is intendet for optimizations. The
+     * implementation may choose to return a different number of elements than
+     * requested.
+     * 
+     * NOTE: The returned vector may contain »unspecified« links. These refer to 
+     * to the own node. (e.g. If there's no closer node, the top element in the 
+     * returned vector is unsoecified.)
+     * 
+     * @param id The destination node id
+     * @param num The desired number of elements in the returned vector.
+     *            (0 means »not specified/max)«
+     * @return A sorted vector of link ids to possible next hops.
+     */
+    virtual std::vector<const LinkID*> getSortedLinkIdsTowardsNode(
+        const NodeID& id, int num = 0 ) const = 0;
+
         /**
          * Returns the NodeID of the next hop a route message would take.
@@ -176 +197 @@
 
         /// @see CommunicationListener
-        virtual void onMessage(const DataMessage& msg, const NodeID& remote,
+        virtual void onMessage(OverlayMsg* msg,
+                reboost::shared_buffer_t sub_msg,
+                const NodeID& remote,
                         const LinkID& lnk = LinkID::UNSPECIFIED);
 

source/ariba/overlay/modules/OverlayStructureEvents.h

@@ -41 +41 @@
 
 #include "ariba/utility/types/NodeID.h"
-#include "ariba/utility/messages.h"
+#include "ariba/utility/types/LinkID.h"
+#include "ariba/utility/messages/Message.h"
 
 using ariba::utility::NodeID;
+using ariba::utility::LinkID;
 using ariba::utility::Message;
 
@@ -50 +52 @@
 
 class OverlayInterface;
-class OneHop;
+//class OneHop;
 
 class OverlayStructureEvents {
         friend class ariba::overlay::OverlayInterface;
-        friend class ariba::overlay::OneHop;
+//      friend class ariba::overlay::OneHop;
 
 public:

source/ariba/overlay/modules/chord/Chord.cpp

@@ -43 +43 @@
 #include "detail/chord_routing_table.hpp"
 
-#include "messages/Discovery.h"
+//#include "messages/Discovery.h"  // XXX DEPRECATED
 
 namespace ariba {
@@ -55 +55 @@
 typedef chord_routing_table::item route_item;
 
+using ariba::transport::system_priority;
+
 use_logging_cpp( Chord );
+
+
+////// Messages
+struct DiscoveryMessage
+{
+    /**
+     * DiscoveryMessage
+     * - type
+     * - data
+     * - Endpoint
+     */
+
+    // type enum
+    enum type_ {
+        invalid = 0,
+        normal = 1,
+        successor = 2,
+        predecessor = 3
+    };
+
+    
+    // data
+    uint8_t type;
+    uint8_t ttl;
+    EndpointDescriptor endpoint;
+
+    // serialize
+    reboost::message_t serialize()
+    {
+        // serialize endpoint
+        reboost::message_t msg = endpoint.serialize();
+        
+        // serialize type and ttl
+        uint8_t* buff1 = msg.push_front(2*sizeof(uint8_t)).mutable_data();
+        buff1[0] = type;
+        buff1[1] = ttl;
+        
+        return msg;
+    }
+    
+    //deserialize
+    reboost::shared_buffer_t deserialize(reboost::shared_buffer_t buff)
+    {
+        // deserialize type and ttl
+        const uint8_t* bytes = buff.data();
+        type = bytes[0];
+        ttl = bytes[1];
+        
+        // deserialize endpoint
+        return endpoint.deserialize(buff(2*sizeof(uint8_t)));
+    }
+};
+
 
 Chord::Chord(BaseOverlay& _baseoverlay, const NodeID& _nodeid,
@@ -102 +157 @@
 
 /// helper: sends a message using the "base overlay"
-seqnum_t Chord::send( OverlayMsg* msg, const LinkID& link ) {
-        if (link.isUnspecified()) return 0;
-        return baseoverlay.send_link( msg, link );
+void Chord::send( OverlayMsg* msg, const LinkID& link ) {
+        if (link.isUnspecified())
+        return;
+    
+        baseoverlay.send_link( msg, link, system_priority::OVERLAY );
+}
+
+void Chord::send_node( OverlayMsg* message, const NodeID& remote )
+{
+    try
+    {
+        baseoverlay.send( message, remote, system_priority::OVERLAY );
+    }
+    catch ( message_not_sent& e )
+    {
+        logging_warn("Chord: Could not send message to " << remote
+                << ": " << e.what());
+    }
 }
 
@@ -116 +186 @@
         OverlayMsg msg( typeDiscovery );
         msg.setRegisterRelay(true);
-        Discovery dmsg( Discovery::normal, (uint8_t)ttl, baseoverlay.getEndpointDescriptor() );
-        msg.encapsulate(&dmsg);
+        
+        // create DiscoveryMessage
+        DiscoveryMessage dmsg;
+        dmsg.type = DiscoveryMessage::normal;
+        dmsg.ttl = ttl;
+        dmsg.endpoint = baseoverlay.getEndpointDescriptor();
+
+        msg.set_payload_message(dmsg.serialize());
 
         // send to node
-        baseoverlay.send_node( &msg, remote );
+    try
+    {
+        baseoverlay.send_node( &msg, remote, system_priority::OVERLAY );
+    }
+    catch ( message_not_sent& e )
+    {
+        logging_warn("Chord: Could not send message to " << remote
+                << ": " << e.what());
+    }
 }
 
 void Chord::discover_neighbors( const LinkID& link ) {
         uint8_t ttl = 1;
+        
+    // FIXME try-catch for the send operations
+    
+    // create DiscoveryMessage
+    DiscoveryMessage dmsg;
+    dmsg.ttl = ttl;
+    dmsg.endpoint = baseoverlay.getEndpointDescriptor();
         {
                 // send predecessor discovery
                 OverlayMsg msg( typeDiscovery );
                 msg.setRegisterRelay(true);
-                Discovery dmsg( Discovery::predecessor, ttl,
-                        baseoverlay.getEndpointDescriptor() );
-                msg.encapsulate(&dmsg);
+
+                // set type
+            dmsg.type = DiscoveryMessage::predecessor;
+
+            // send
+            msg.set_payload_message(dmsg.serialize());
                 send(&msg, link);
         }
@@ -137 +231 @@
                 // send successor discovery
                 OverlayMsg msg( typeDiscovery );
-                msg.setSourceEndpoint( baseoverlay.getEndpointDescriptor() );
+//              msg.setSourceEndpoint( baseoverlay.getEndpointDescriptor() );  // XXX this was redundand, wasn't it?
                 msg.setRegisterRelay(true);
-                Discovery dmsg( Discovery::successor, ttl,
-                        baseoverlay.getEndpointDescriptor() );
-                msg.encapsulate(&dmsg);
+
+                // set type
+        dmsg.type = DiscoveryMessage::successor;
+
+        // send
+        msg.set_payload_message(dmsg.serialize());
                 send(&msg, link);
         }
@@ -163 +260 @@
 
         // timer for stabilization management
-        Timer::setInterval(1000);
+//      Timer::setInterval(1000);  // TODO find an appropriate interval!
+        Timer::setInterval(10000);  // XXX testing...
         Timer::start();
 }
@@ -200 +298 @@
         return item->info;
 }
+
+std::vector<const LinkID*> Chord::getSortedLinkIdsTowardsNode(
+    const NodeID& id, int num ) const
+{
+    std::vector<const LinkID*> ret;
+    
+    switch ( num )
+    {
+        // special case: just call »getNextLinkId«
+        case 1:
+        {
+            ret.push_back(&getNextLinkId(id));
+            
+            break;
+        }
+        
+        // * calculate top 2 *
+        case 0:
+        case 2:
+        {
+            std::vector<const route_item*> items = table->get_next_2_hops(id);
+            
+            ret.reserve(items.size());
+            
+            BOOST_FOREACH( const route_item* item, items )
+            {
+                ret.push_back(&item->info);
+            }
+            
+            break;
+        }
+        
+        // NOTE: implement real sorting, if needed (and handle "case 0" properly, then)
+        default:
+        {
+            throw std::runtime_error("Not implemented. (Chord::getSortedLinkIdsTowardsNode with num != 2)");
+            
+            break;
+        }
+    }
+    
+    return ret;
+}
+
 
 /// @see OverlayInterface.h
@@ -253 +395 @@
         if (remote==nodeid) {
                 logging_warn("dropping link that has been established to myself (nodes have same nodeid?)");
+                logging_warn("NodeID: " << remote);
                 baseoverlay.dropLink(lnk);
                 return;
@@ -290 +433 @@
 /// @see CommunicationListener.h or @see OverlayInterface.h
 void Chord::onLinkDown(const LinkID& lnk, const NodeID& remote) {
-        logging_debug("link_down: link=" << lnk.toString() << " remote=" <<
+    // XXX logging_debug
+        logging_info("link_down (Chord): link=" << lnk.toString() << " remote=" <<
                         remote.toString() );
 
@@ -303 +447 @@
 /// @see CommunicationListener.h
 /// @see OverlayInterface.h
-void Chord::onMessage(const DataMessage& msg, const NodeID& remote,
+void Chord::onMessage(OverlayMsg* msg,
+        reboost::shared_buffer_t sub_msg,
+        const NodeID& remote,
                 const LinkID& link) {
 
-        // decode message
-        OverlayMsg* m = dynamic_cast<OverlayMsg*>(msg.getMessage());
-        if (m == NULL) return;
-
         // handle messages
-        switch ((signalMessageTypes)m->getType()) {
+        switch ((signalMessageTypes) msg->getType()) {
 
         // discovery request
-        case typeDiscovery: {
-                // decapsulate message
-                Discovery* dmsg = m->decapsulate<Discovery> ();
+        case typeDiscovery:
+        {
+                // deserialize discovery message
+                DiscoveryMessage dmsg;
+                dmsg.deserialize(sub_msg);
+                
                 logging_debug("Received discovery message with"
-                            << " src=" << m->getSourceNode().toString()
-                                << " dst=" << m->getDestinationNode().toString()
-                                << " ttl=" << (int)dmsg->getTTL()
-                                << " type=" << (int)dmsg->getType()
+                            << " src=" << msg->getSourceNode().toString()
+                                << " dst=" << msg->getDestinationNode().toString()
+                                << " ttl=" << (int)dmsg.ttl
+                                << " type=" << (int)dmsg.type
                 );
 
@@ -327 +472 @@
                 bool found = false;
                 BOOST_FOREACH( NodeID& value, discovery )
-                        if (value == m->getSourceNode()) {
+                        if (value == msg->getSourceNode()) {
                                 found = true;
                                 break;
                         }
-                if (!found) discovery.push_back(m->getSourceNode());
+                if (!found) discovery.push_back(msg->getSourceNode());
 
                 // check if source node can be added to routing table and setup link
-                if (m->getSourceNode() != nodeid)
-                        setup( dmsg->getEndpoint(), m->getSourceNode() );
+                if (msg->getSourceNode() != nodeid)
+                        setup( dmsg.endpoint, msg->getSourceNode() );
 
                 // process discovery message -------------------------- switch start --
-                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()) ) {
-                                logging_debug("Discovery split:");
-                                if (!table->get_successor()->isUnspecified()) {
-                                        OverlayMsg omsg(*m);
-                                        dmsg->setType(Discovery::successor);
-                                        omsg.encapsulate(dmsg);
-                                        logging_debug("* Routing to successor "
-                                                        << table->get_successor()->toString() );
-                                        baseoverlay.send( &omsg, *table->get_successor() );
-                                }
-
-                                // send predecessor message
-                                if (!table->get_predesessor()->isUnspecified()) {
-                                        OverlayMsg omsg(*m);
-                                        dmsg->setType(Discovery::predecessor);
-                                        omsg.encapsulate(dmsg);
-                                        logging_debug("* Routing to predecessor "
-                                                        << table->get_predesessor()->toString() );
-                                        baseoverlay.send( &omsg, *table->get_predesessor() );
-                                }
-                        }
-                        // no-> route message
-                        else {
-                                baseoverlay.route( m );
-                        }
-                        break;
-                }
-
-                // successor mode: follow the successor until TTL is zero
-                case Discovery::successor:
-                case Discovery::predecessor: {
-                        // reached destination? no->forward!
-                        if (m->getDestinationNode() != nodeid) {
-                                OverlayMsg omsg(*m);
-                                omsg.encapsulate(dmsg);
-                                omsg.setService(OverlayInterface::OVERLAY_SERVICE_ID);
-                                baseoverlay.route( &omsg );
-                                break;
-                        }
-
-                        // 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);
-                        omsg.setService(OverlayInterface::OVERLAY_SERVICE_ID);
-                        baseoverlay.send(&omsg, omsg.getDestinationNode());
-                        break;
-                }
-                case Discovery::invalid:
-                        break;
-
-                default:
-                        break;
-                }
-                // process discovery message ---------------------------- switch end --
-
-                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;
-        }}
+                switch ( dmsg.type )
+                {
+            // normal: route discovery message like every other message
+            case DiscoveryMessage::normal:
+            {
+                // closest node? yes-> split to follow successor and predecessor
+                if ( table->is_closest_to(msg->getDestinationNode()) )
+                {
+                    logging_debug("Discovery split:");
+                    if (!table->get_successor()->isUnspecified())
+                    {
+                        OverlayMsg omsg(*msg);
+                        
+                        dmsg.type = DiscoveryMessage::successor;
+                        omsg.set_payload_message(dmsg.serialize());
+
+                        logging_debug("* Routing to successor "
+                                << table->get_successor()->toString() );
+                        send_node( &omsg, *table->get_successor() );
+                    }
+    
+                    // send predecessor message
+                    if (!table->get_predesessor()->isUnspecified())
+                    {
+                        OverlayMsg omsg(*msg);
+                        
+                        dmsg.type = DiscoveryMessage::predecessor;
+                        omsg.set_payload_message(dmsg.serialize());
+
+                        logging_debug("* Routing to predecessor "
+                                << table->get_predesessor()->toString() );
+                        send_node( &omsg, *table->get_predesessor() );
+                    }
+                }
+                // no-> route message
+                else
+                {
+                    baseoverlay.route( msg );
+                }
+                break;
+            }
+    
+            // successor mode: follow the successor until TTL is zero
+            case DiscoveryMessage::successor:
+            case DiscoveryMessage::predecessor:
+            {
+                // reached destination? no->forward!
+                if (msg->getDestinationNode() != nodeid)
+                {
+                    OverlayMsg omsg(*msg);
+                    omsg.setService(OverlayInterface::OVERLAY_SERVICE_ID);
+                    
+                    omsg.set_payload_message(dmsg.serialize());
+                    
+                    baseoverlay.route( &omsg );
+                    break;
+                }
+    
+                // time to live ended? yes-> stop routing
+                if (dmsg.ttl == 0 || dmsg.ttl > 10) break;
+    
+                // decrease time-to-live
+                dmsg.ttl--;
+    
+                const route_item* item = NULL;
+                if (dmsg.type == DiscoveryMessage::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(*msg);
+                omsg.setService(OverlayInterface::OVERLAY_SERVICE_ID);
+                omsg.setDestinationNode(item->id);
+                
+                omsg.set_payload_message(dmsg.serialize());
+                
+                send_node( &omsg, omsg.getDestinationNode() );
+                break;
+            }
+            case DiscoveryMessage::invalid:
+                break;
+    
+            default:
+                break;
+            }
+            // process discovery message ---------------------------- switch end --
+    
+            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;
+        }
+        }
 }
 

source/ariba/overlay/modules/chord/Chord.h

@@ -45 +45 @@
 #include "../OverlayInterface.h"
 #include <vector>
+#include <stdexcept>
 
 class chord_routing_table;
@@ -87 +88 @@
                 const NodeID& node = NodeID::UNSPECIFIED );
 
-        // helper: sends a message using the "base overlay"
-        seqnum_t send( OverlayMsg* msg, const LinkID& link );
+        // helper: sends a message over a link using the "base overlay"
+        void send( OverlayMsg* msg, const LinkID& link );
 
+        // helper: sends a message to a node using the "base overlay"
+        void send_node( OverlayMsg* message, const NodeID& remote );
+                
         // stabilization: sends a discovery message to the specified neighborhood
         void send_discovery_to( const NodeID& destination, int ttl = 3 );
@@ -105 +109 @@
         virtual const LinkID& getNextLinkId( const NodeID& id ) const;
         
+    /// @see OverlayInterface.h
+    /// NOTE: This implementation excepts num == 2
+    virtual std::vector<const LinkID*> getSortedLinkIdsTowardsNode(
+        const NodeID& id, int num = 0 ) const;
+
         /// @see OverlayInterface.h
         virtual const NodeID& getNextNodeId( const NodeID& id ) const;
@@ -138 +147 @@
 
         /// @see CommunicationListener.h or @see OverlayInterface.h
-        virtual void onMessage(const DataMessage& msg, const NodeID& remote,
+        virtual void onMessage(OverlayMsg* msg,
+                reboost::shared_buffer_t sub_msg,
+                const NodeID& remote,
                         const LinkID& lnk = LinkID::UNSPECIFIED);
 

source/ariba/overlay/modules/chord/detail/chord_routing_table.hpp

@@ -96 +96 @@
         // the own node id
         nodeid_t id;
+    
+    // the own node id as routing item
+    item own_id_item;
 
         // successor and predecessor tables
@@ -168 +171 @@
         /// constructs the reactive chord routing table
         explicit chord_routing_table( const nodeid_t& id, int redundancy = 4 ) :
-                id(id), succ( redundancy, succ_compare_type(this->id), *this ),
-                pred( redundancy, pred_compare_type(this->id), *this ) {
+                id(id),
+                succ( redundancy, succ_compare_type(this->id), *this ),
+                pred( redundancy, pred_compare_type(this->id), *this )
+    {
+        // init reflexive item
+        own_id_item.id = id;
+        own_id_item.ref_count = 1;
 
                 // create finger tables
@@ -273 +281 @@
                         }
                 }
+
                 if (best_item != NULL && distance(value, id)<distance(value, best_item->id))
                         return NULL;
                 return best_item;
         }
+        
+        std::vector<const item*> get_next_2_hops( const nodeid_t& value)
+    {
+        ring_distance distance;
+        item* best_item = &own_id_item;
+        item* second_best_item = NULL;
+        
+        // find best and second best item
+        for (size_t i=0; i<table.size(); i++)
+        {
+            item* curr = &table[i];
+
+            // not not include orphans into routing!
+            if (curr->ref_count==0) continue;
+
+            // check if we found a better item
+            // is best item
+            if ( distance(value, curr->id) < distance(value, best_item->id) )
+            {
+                second_best_item = best_item;
+                best_item = curr;
+            }
+            // is second best item
+            else
+            {
+                if ( second_best_item == NULL )
+                {
+                    second_best_item = curr;
+                    continue;
+                }
+                
+                if ( distance(value, curr->id) < distance(value, second_best_item->id) )
+                {
+                    second_best_item = curr;
+                }
+            }
+        }
+
+        // prepare return vector
+        std::vector<const item*> ret;
+        if ( best_item != NULL )
+        {
+            ret.push_back(best_item);
+        }
+        if ( second_best_item != NULL )
+        {
+            ret.push_back(second_best_item);
+        }
+        
+        return ret;
+    }
 
         const nodeid_t* get_successor() {
-                if (succ.size()==NULL) return NULL;
+                if (succ.size()==0) return NULL;
                 return &succ.front();
         }
 
         const nodeid_t* get_predesessor() {
-                if (pred.size()==NULL) return NULL;
+                if (pred.size()==0) return NULL;
                 return &pred.front();
         }

source/ariba/overlay/modules/chord/messages/CMakeLists.txt

@@ -37 +37 @@
 # [License]
 
-add_headers(Discovery.h)
+#add_headers(Discovery.h)
 
-add_sources(Discovery.cpp)
+#add_sources(Discovery.cpp)

source/ariba/overlay/modules/chord/messages/Discovery.h

@@ -59 +59 @@
 using_serialization;
 
+// XXX This whole message is DEPRECATED
 class Discovery : public Message {
         VSERIALIZEABLE;

source/ariba/overlay/modules/onehop/CMakeLists.txt

@@ -37 +37 @@
 # [License]
 
-add_headers(OneHop.h)
 
-add_sources(OneHop.cpp)
+## DEPRECATED
+#add_headers(OneHop.h)
 
-add_subdir_sources(messages)
+#add_sources(OneHop.cpp)
+
+#add_subdir_sources(messages)