21 files changed, 484 insertions, 305 deletions
diff --git a/cpp/demo/IceGrid/replication/config.node1 b/cpp/demo/IceGrid/replication/config.node1
index 42c70b30bca..007b3e1081c 100644
--- a/cpp/demo/IceGrid/replication/config.node1
+++ b/cpp/demo/IceGrid/replication/config.node1
@@ -4,6 +4,14 @@
 Ice.Default.Locator=ReplicationDemoIceGrid/Locator:default -h localhost -p 12000 -t 10000:default -h localhost -p 12001 -t 10000:default -h localhost -p 12002 -t 10000
 
 #
+# To use the IceGrid discovery plugin comment out the default locator
+# property above and un-comment the two properties below. The discovery
+# plugin uses multicast to discover IceGrid.
+#
+#Ice.Plugin.IceGridDiscovery=IceGrid:createIceGridDiscovery
+#IceGrid.InstanceName=ReplicationDemoIceGrid
+
+#
 # IceGrid node configuration.
 #
 IceGrid.Node.Name=node1
diff --git a/cpp/demo/IceGrid/replication/config.node2 b/cpp/demo/IceGrid/replication/config.node2
index a8def29fc15..b787aa62edb 100644
--- a/cpp/demo/IceGrid/replication/config.node2
+++ b/cpp/demo/IceGrid/replication/config.node2
@@ -4,6 +4,14 @@
 Ice.Default.Locator=ReplicationDemoIceGrid/Locator:default -h localhost -p 12000 -t 10000:default -h localhost -p 12001 -t 10000:default -h localhost -p 12002 -t 10000
 
 #
+# To use the IceGrid discovery plugin comment out the default locator
+# property above and un-comment the two properties below. The discovery
+# plugin uses multicast to discover IceGrid.
+#
+#Ice.Plugin.IceGridDiscovery=IceGrid:createIceGridDiscovery
+#IceGrid.InstanceName=ReplicationDemoIceGrid
+
+#
 # IceGrid node configuration.
 #
 IceGrid.Node.Name=node2
diff --git a/cpp/demo/IceGrid/replication/config.replica1 b/cpp/demo/IceGrid/replication/config.replica1
index 7d3d886061f..e23bd32f2a5 100644
--- a/cpp/demo/IceGrid/replication/config.replica1
+++ b/cpp/demo/IceGrid/replication/config.replica1
@@ -4,6 +4,14 @@
 Ice.Default.Locator=ReplicationDemoIceGrid/Locator:default -h localhost -p 12000 -t 10000:default -h localhost -p 12002 -t 10000
 
 #
+# To use the IceGrid discovery plugin comment out the default locator
+# property above and un-comment the two properties below. The discovery
+# plugin uses multicast to discover IceGrid.
+#
+#Ice.Plugin.IceGridDiscovery=IceGrid:createIceGridDiscovery
+#IceGrid.InstanceName=ReplicationDemoIceGrid
+
+#
 # IceGrid registry configuration.
 #
 IceGrid.Registry.Client.Endpoints=default -h localhost -p 12001 -t 10000
diff --git a/cpp/demo/IceGrid/replication/config.replica2 b/cpp/demo/IceGrid/replication/config.replica2
index 11c1f03dd48..e122e707a47 100644
--- a/cpp/demo/IceGrid/replication/config.replica2
+++ b/cpp/demo/IceGrid/replication/config.replica2
@@ -4,6 +4,14 @@
 Ice.Default.Locator=ReplicationDemoIceGrid/Locator:default -h localhost -p 12000 -t 10000:default -h localhost -p 12001 -t 10000
 
 #
+# To use the IceGrid discovery plugin comment out the default locator
+# property above and un-comment the two properties below. The discovery
+# plugin uses multicast to discover IceGrid.
+#
+#Ice.Plugin.IceGridDiscovery=IceGrid:createIceGridDiscovery
+#IceGrid.InstanceName=ReplicationDemoIceGrid
+
+#
 # IceGrid registry configuration.
 #
 IceGrid.Registry.Client.Endpoints=default -h localhost -p 12002 -t 10000
diff --git a/cpp/demo/IceGrid/replication/expect.py b/cpp/demo/IceGrid/replication/expect.py
index ed1f93c1b5e..d28f664c6d1 100755
--- a/cpp/demo/IceGrid/replication/expect.py
+++ b/cpp/demo/IceGrid/replication/expect.py
@@ -35,72 +35,88 @@ if Util.defaultHost:
 else:
     args = ''
 
-sys.stdout.write("starting icegridnodes... ")
-sys.stdout.flush()
-master = Util.spawn(Util.getIceGridRegistry() + ' --Ice.Config=config.master --Ice.PrintAdapterReady --Ice.StdErr= --Ice.StdOut=')
-master.expect('IceGrid.Registry.Internal ready\nIceGrid.Registry.Server ready\nIceGrid.Registry.Client ready')
-replica1 = Util.spawn(Util.getIceGridRegistry() + ' --Ice.Config=config.replica1 --Ice.PrintAdapterReady --Ice.StdErr= --Ice.StdOut=')
-replica1.expect('IceGrid.Registry.Server ready\nIceGrid.Registry.Client ready')
-replica2 = Util.spawn(Util.getIceGridRegistry() + ' --Ice.Config=config.replica2 --Ice.PrintAdapterReady --Ice.StdErr= --Ice.StdOut=')
-replica2.expect('IceGrid.Registry.Server ready\nIceGrid.Registry.Client ready')
-node1 = Util.spawn(Util.getIceGridNode() + ' --Ice.Config=config.node1 --Ice.PrintAdapterReady --Ice.StdErr= --Ice.StdOut= %s' % (args))
-node1.expect('IceGrid.Node ready')
-node2 = Util.spawn(Util.getIceGridNode() + ' --Ice.Config=config.node2 --Ice.PrintAdapterReady --Ice.StdErr= --Ice.StdOut= %s' % (args))
-node2.expect('IceGrid.Node ready')
-print("ok")
+def runDemo(properties, clientProperties):
 
-sys.stdout.write("deploying application... ")
-sys.stdout.flush()
-admin = Util.spawn(Util.getIceGridAdmin() + ' --Ice.Config=config.client')
-admin.expect('>>>')
-admin.sendline("application add \'application.xml\'")
-admin.expect('>>>')
-print("ok")
+    sys.stdout.write("starting icegridnodes... ")
+    sys.stdout.flush()
+    master = Util.spawn(Util.getIceGridRegistry() + properties + ' --Ice.Config=config.master ')
+    master.expect('IceGrid.Registry.Internal ready\nIceGrid.Registry.Server ready\nIceGrid.Registry.Client ready')
+    replica1 = Util.spawn(Util.getIceGridRegistry() + properties + ' --Ice.Config=config.replica1')
+    replica1.expect('IceGrid.Registry.Server ready\nIceGrid.Registry.Client ready')
+    replica2 = Util.spawn(Util.getIceGridRegistry() + properties + ' --Ice.Config=config.replica2')
+    replica2.expect('IceGrid.Registry.Server ready\nIceGrid.Registry.Client ready')
+    node1 = Util.spawn(Util.getIceGridNode() + properties + ' --Ice.Config=config.node1 %s' % (args))
+    node1.expect('IceGrid.Node ready')
+    node2 = Util.spawn(Util.getIceGridNode() + properties + ' --Ice.Config=config.node2 %s' % (args))
+    node2.expect('IceGrid.Node ready')
+    print("ok")
 
-def runtest():
-    client = Util.spawn('./client')
-    client.expect('iterations:')
-    client.sendline('5')
-    client.expect('\(in ms\):')
-    client.sendline('0')
-    for i in range(1, 5):
-        client.expect("Hello World!")
-    client.sendline('x')
-    client.sendline('x')
+    sys.stdout.write("deploying application... ")
+    sys.stdout.flush()
+    admin = Util.spawn(Util.getIceGridAdmin() + ' --Ice.Config=config.client')
+    admin.expect('>>>')
+    admin.sendline("application add \'application.xml\'")
+    admin.expect('>>>')
+    print("ok")
 
-    client.waitTestSuccess(timeout=1)
+    def runtest():
+        client = Util.spawn('./client ' + clientProperties)
+        client.expect('iterations:')
+        client.sendline('5')
+        client.expect('\(in ms\):')
+        client.sendline('0')
+        for i in range(1, 5):
+            client.expect("Hello World!")
+        client.sendline('x')
+        client.sendline('x')
 
-sys.stdout.write("testing client... ")
-sys.stdout.flush()
-runtest()
-print("ok")
+        client.waitTestSuccess(timeout=1)
 
-sys.stdout.write("testing replication... ")
-sys.stdout.flush()
-admin.sendline('registry shutdown Replica1')
-admin.expect('>>>')
-replica1.waitTestSuccess()
-runtest()
-admin.sendline('registry shutdown Replica2')
-admin.expect('>>>')
-replica2.waitTestSuccess()
-runtest()
-print("ok")
+    sys.stdout.write("testing client... ")
+    sys.stdout.flush()
+    runtest()
+    print("ok")
 
-sys.stdout.write("completing shutdown... ")
-sys.stdout.flush()
-admin.sendline('node shutdown node1')
-admin.expect('>>>')
-node1.waitTestSuccess(timeout=120)
+    sys.stdout.write("testing replication... ")
+    sys.stdout.flush()
+    admin.sendline('registry shutdown Replica1')
+    admin.expect('>>>')
+    replica1.waitTestSuccess()
+    runtest()
+    admin.sendline('registry shutdown Replica2')
+    admin.expect('>>>')
+    replica2.waitTestSuccess()
+    runtest()
+    print("ok")
 
-admin.sendline('node shutdown node2')
-admin.expect('>>>')
-node2.waitTestSuccess(timeout=120)
+    sys.stdout.write("completing shutdown... ")
+    sys.stdout.flush()
+    admin.sendline('node shutdown node1')
+    admin.expect('>>>')
+    node1.waitTestSuccess(timeout=120)
 
-admin.sendline('registry shutdown Master')
-admin.expect('>>>')
-master.waitTestSuccess()
+    admin.sendline('node shutdown node2')
+    admin.expect('>>>')
+    node2.waitTestSuccess(timeout=120)
 
-admin.sendline('exit')
-admin.waitTestSuccess(timeout=120)
-print("ok")
+    admin.sendline("application remove Simple")
+    admin.expect('>>>')
+
+    admin.sendline('registry shutdown Master')
+    admin.expect('>>>')
+    master.waitTestSuccess()
+
+    admin.sendline('exit')
+    admin.waitTestSuccess(timeout=120)
+    print("ok")
+
+print("running with Ice.Default.Locator set")
+properties = ' --Ice.PrintAdapterReady --Ice.StdErr= --Ice.StdOut='
+runDemo(properties, '')
+
+print("running with IceGridDiscovery")
+discovery = ' --Ice.Plugin.IceGridDiscovery=IceGrid:createIceGridDiscovery' + \
+            ' --IceGridDiscovery.InstanceName=ReplicationDemoIceGrid' + \
+            ' --Ice.Default.Locator='
+properties = ' --Ice.PrintAdapterReady --Ice.StdErr= --Ice.StdOut= --Ice.Default.Locator='
+runDemo(properties + discovery, discovery)
diff --git a/cpp/src/Ice/LocatorInfo.cpp b/cpp/src/Ice/LocatorInfo.cpp
index dfdadb06c86..e668dc3a248 100644
--- a/cpp/src/Ice/LocatorInfo.cpp
+++ b/cpp/src/Ice/LocatorInfo.cpp
@@ -540,7 +540,11 @@ IceInternal::LocatorInfo::getLocatorRegistry()
     // Do not make locator calls from within sync.
     //
     LocatorRegistryPrx locatorRegistry = _locator->getRegistry();
-    
+    if(!locatorRegistry)
+    {
+        return 0;
+    }
+
     {
         IceUtil::Mutex::Lock sync(*this);
 
diff --git a/cpp/src/IceGrid/IceGridNode.cpp b/cpp/src/IceGrid/IceGridNode.cpp
index 183de011e10..089f2d49c26 100644
--- a/cpp/src/IceGrid/IceGridNode.cpp
+++ b/cpp/src/IceGrid/IceGridNode.cpp
@@ -331,6 +331,8 @@ NodeService::startImpl(int argc, char* argv[], int& status)
             return false;
         }
 
+        communicator()->setDefaultLocator(_registry->getLocator());
+        
         //
         // Set the default locator property to point to the collocated
         // locator (this property is passed by the activator to each
@@ -339,16 +341,10 @@ NodeService::startImpl(int argc, char* argv[], int& status)
         //
         if(properties->getProperty("Ice.Default.Locator").empty())
         {
-            Identity locatorId;
-            locatorId.category = properties->getPropertyWithDefault("IceGrid.InstanceName", "IceGrid");
-            locatorId.name = "Locator";
-            string endpoints = properties->getProperty("IceGrid.Registry.Client.Endpoints");
-            string locPrx = "\"" + communicator()->identityToString(locatorId) + "\" :" + endpoints;
-            communicator()->setDefaultLocator(Ice::LocatorPrx::uncheckedCast(communicator()->stringToProxy(locPrx)));
-            properties->setProperty("Ice.Default.Locator", locPrx);
+            properties->setProperty("Ice.Default.Locator", communicator()->getDefaultLocator()->ice_toString());
         }
     }
-    else if(properties->getProperty("Ice.Default.Locator").empty())
+    else if(!communicator()->getDefaultLocator())
     {
         error("property `Ice.Default.Locator' is not set");
         return false;
@@ -485,9 +481,21 @@ NodeService::startImpl(int argc, char* argv[], int& status)
     //
     // The IceGrid instance name.
     //
-    const string instanceName = communicator()->getDefaultLocator()->ice_getIdentity().category;
+    string instanceName = properties->getProperty("IceGrid.InstanceName");
+    if(instanceName.empty())
+    {
+        instanceName = properties->getProperty("IceGridDiscovery.InstanceName");
+    }
+    if(instanceName.empty())
+    {
+        instanceName = communicator()->getDefaultLocator()->ice_getIdentity().category;
+    }
+    if(instanceName.empty())
+    {
+        instanceName = "IceGrid";
+    }
 
-    _sessions.reset(new NodeSessionManager(communicator()));
+    _sessions.reset(new NodeSessionManager(communicator(), instanceName));
 
     //
     // Create the server factory. The server factory creates persistent objects
@@ -496,7 +504,7 @@ NodeService::startImpl(int argc, char* argv[], int& status)
     //
     Identity id = communicator()->stringToIdentity(instanceName + "/Node-" + name);
     NodePrx nodeProxy = NodePrx::uncheckedCast(_adapter->createProxy(id));
-    _node = new NodeI(_adapter, *_sessions, _activator, _timer, traceLevels, nodeProxy, name, mapper);
+    _node = new NodeI(_adapter, *_sessions, _activator, _timer, traceLevels, nodeProxy, name, mapper, instanceName);
     _adapter->add(_node, nodeProxy->ice_getIdentity());
 
     _adapter->addServantLocator(new DefaultServantLocator(new NodeServerAdminRouter(_node)), 
@@ -516,7 +524,7 @@ NodeService::startImpl(int argc, char* argv[], int& status)
         {
             communicator()->getDefaultLocator()->ice_timeout(1000)->ice_ping();
         }
-        catch(const Ice::LocalException& ex)
+        catch(const Ice::Exception& ex)
         {
             Warning out(communicator()->getLogger());
             out << "couldn't reach the IceGrid registry (this is expected ";
diff --git a/cpp/src/IceGrid/NodeI.cpp b/cpp/src/IceGrid/NodeI.cpp
index 5e3fdacf906..97c4c077b7e 100644
--- a/cpp/src/IceGrid/NodeI.cpp
+++ b/cpp/src/IceGrid/NodeI.cpp
@@ -299,7 +299,8 @@ NodeI::NodeI(const Ice::ObjectAdapterPtr& adapter,
              const TraceLevelsPtr& traceLevels,
              const NodePrx& proxy,
              const string& name,
-             const UserAccountMapperPrx& mapper) :
+             const UserAccountMapperPrx& mapper,
+             const string& instanceName) :
     _communicator(adapter->getCommunicator()),
     _adapter(adapter),
     _sessions(sessions),
@@ -311,6 +312,7 @@ NodeI::NodeI(const Ice::ObjectAdapterPtr& adapter,
     _redirectErrToOut(false),
     _allowEndpointsOverride(false),
     _waitTime(0),
+    _instanceName(instanceName),
     _userAccountMapper(mapper),
     _platform("IceGrid.Node", _communicator, _traceLevels),
     _fileCache(new FileCache(_communicator)),
@@ -322,7 +324,6 @@ NodeI::NodeI(const Ice::ObjectAdapterPtr& adapter,
     const_cast<string&>(_dataDir) = _platform.getDataDir();
     const_cast<string&>(_serversDir) = _dataDir + "/servers";
     const_cast<string&>(_tmpDir) = _dataDir + "/tmp";
-    const_cast<string&>(_instanceName) = _communicator->getDefaultLocator()->ice_getIdentity().category;
     const_cast<Ice::Int&>(_waitTime) = props->getPropertyAsIntWithDefault("IceGrid.Node.WaitTime", 60);
     const_cast<string&>(_outputDir) = props->getProperty("IceGrid.Node.Output");
     const_cast<bool&>(_redirectErrToOut) = props->getPropertyAsInt("IceGrid.Node.RedirectErrToOut") > 0;
@@ -903,6 +904,12 @@ NodeI::getPropertiesOverride() const
     return _propertiesOverride;
 }
 
+const string&
+NodeI::getInstanceName() const
+{
+    return _instanceName;
+}
+
 string
 NodeI::getOutputDir() const
 {
diff --git a/cpp/src/IceGrid/NodeI.h b/cpp/src/IceGrid/NodeI.h
index f212a71b4c6..b438af7ffef 100644
--- a/cpp/src/IceGrid/NodeI.h
+++ b/cpp/src/IceGrid/NodeI.h
@@ -63,7 +63,7 @@ public:
     typedef IceUtil::Handle<Update> UpdatePtr;
 
     NodeI(const Ice::ObjectAdapterPtr&, NodeSessionManager&, const ActivatorPtr&, const IceUtil::TimerPtr&, 
-          const TraceLevelsPtr&, const NodePrx&, const std::string&, const UserAccountMapperPrx&);
+          const TraceLevelsPtr&, const NodePrx&, const std::string&, const UserAccountMapperPrx&, const std::string&);
     virtual ~NodeI();
 
     virtual void loadServer_async(const AMD_Node_loadServerPtr&, 
@@ -119,6 +119,7 @@ public:
     FileCachePtr getFileCache() const;
     NodePrx getProxy() const;
     const PropertyDescriptorSeq& getPropertiesOverride() const;
+    const std::string& getInstanceName() const;
 
     std::string getOutputDir() const;
     bool getRedirectErrToOut() const;
diff --git a/cpp/src/IceGrid/NodeSessionManager.cpp b/cpp/src/IceGrid/NodeSessionManager.cpp
index 5a71048a511..5d361f5ce7e 100644
--- a/cpp/src/IceGrid/NodeSessionManager.cpp
+++ b/cpp/src/IceGrid/NodeSessionManager.cpp
@@ -16,14 +16,12 @@
 using namespace std;
 using namespace IceGrid;
 
-NodeSessionKeepAliveThread::NodeSessionKeepAliveThread(const InternalRegistryPrx& registry,
+NodeSessionKeepAliveThread::NodeSessionKeepAliveThread(const InternalRegistryPrx& registry, 
                                                        const NodeIPtr& node,
-                                                       const vector<QueryPrx>& queryObjects) : 
-    SessionKeepAliveThread<NodeSessionPrx>(registry, node->getTraceLevels()->logger),
-    _node(node),
-    _queryObjects(queryObjects)
+                                                       NodeSessionManager& manager) : 
+    SessionKeepAliveThread<NodeSessionPrx>(registry, node->getTraceLevels()->logger), _node(node), _manager(manager)
 {
-    assert(registry && node && !_queryObjects.empty());
+    assert(registry && node);
     string name = registry->ice_getIdentity().name;
     const string prefix("InternalRegistry-");
     string::size_type pos = name.find(prefix);
@@ -66,7 +64,8 @@ NodeSessionKeepAliveThread::createSession(InternalRegistryPrx& registry, IceUtil
         if(!session)
         {
             vector<Ice::AsyncResultPtr> results;
-            for(vector<QueryPrx>::const_iterator q = _queryObjects.begin(); q != _queryObjects.end(); ++q)
+            vector<QueryPrx> queryObjects = _manager.getQueryObjects();
+            for(vector<QueryPrx>::const_iterator q = queryObjects.begin(); q != queryObjects.end(); ++q)
             {
                 results.push_back((*q)->begin_findObjectById(registry->ice_getIdentity()));
             }
@@ -227,8 +226,8 @@ NodeSessionKeepAliveThread::keepAlive(const NodeSessionPrx& session)
     }
 }
 
-NodeSessionManager::NodeSessionManager(const Ice::CommunicatorPtr& communicator) : 
-    SessionManager(communicator),
+NodeSessionManager::NodeSessionManager(const Ice::CommunicatorPtr& communicator, const string& instanceName) : 
+    SessionManager(communicator, instanceName),
     _destroyed(false),
     _activated(false)
 {
@@ -251,7 +250,8 @@ NodeSessionManager::create(const NodeIPtr& node)
     // with replicas (see createdSession below) and this must be done 
     // before the node is activated.
     //
-    _thread->tryCreateSession(true, IceUtil::Time::seconds(3));
+    _thread->tryCreateSession();
+    _thread->waitTryCreateSession(IceUtil::Time::seconds(3));
 }
 
 void
@@ -273,6 +273,7 @@ NodeSessionManager::create(const InternalRegistryPrx& replica)
     if(thread)
     {
         thread->tryCreateSession();
+        thread->waitTryCreateSession();
     }
 }
 
@@ -370,7 +371,7 @@ NodeSessionManager::replicaInit(const InternalRegistryPrxSeq& replicas)
     for(InternalRegistryPrxSeq::const_iterator p = replicas.begin(); p != replicas.end(); ++p)
     {
         _replicas.insert((*p)->ice_getIdentity());
-        addReplicaSession(*p)->tryCreateSession(false);
+        addReplicaSession(*p)->tryCreateSession();
     }
 }
 
@@ -383,7 +384,7 @@ NodeSessionManager::replicaAdded(const InternalRegistryPrx& replica)
         return;
     }
     _replicas.insert(replica->ice_getIdentity());
-    addReplicaSession(replica)->tryCreateSession(false);
+    addReplicaSession(replica)->tryCreateSession();
 }
 
 void
@@ -408,7 +409,6 @@ NodeSessionKeepAliveThreadPtr
 NodeSessionManager::addReplicaSession(const InternalRegistryPrx& replica)
 {
     assert(!_destroyed);
-
     NodeSessionMap::const_iterator p = _sessions.find(replica->ice_getIdentity());
     NodeSessionKeepAliveThreadPtr thread;
     if(p != _sessions.end())
@@ -418,7 +418,7 @@ NodeSessionManager::addReplicaSession(const InternalRegistryPrx& replica)
     }
     else
     {
-        thread = new NodeSessionKeepAliveThread(replica, _node, _queryObjects);
+        thread = new NodeSessionKeepAliveThread(replica, _node, *this);
         _sessions.insert(make_pair(replica->ice_getIdentity(), thread));
         thread->start();
     }
@@ -535,7 +535,7 @@ NodeSessionManager::createdSession(const NodeSessionPrx& session)
     {
         vector<Ice::AsyncResultPtr> results1;
         vector<Ice::AsyncResultPtr> results2;
-        vector<QueryPrx> queryObjects = findAllQueryObjects();
+        vector<QueryPrx> queryObjects = findAllQueryObjects(false);
 
         //
         // Below we try to retrieve internal registry proxies either
@@ -576,7 +576,7 @@ NodeSessionManager::createdSession(const NodeSessionPrx& session)
             }
             catch(const Ice::LocalException&)
             {
-                // IGNORE
+                // Ignore.
             }
         }
         for(vector<Ice::AsyncResultPtr>::const_iterator p = results2.begin(); p != results2.end(); ++p)
@@ -609,7 +609,7 @@ NodeSessionManager::createdSession(const NodeSessionPrx& session)
             }
             catch(const Ice::LocalException&)
             {
-                // IGNORE
+                // Ignore
             }
         }
 
@@ -639,9 +639,17 @@ NodeSessionManager::createdSession(const NodeSessionPrx& session)
                 if((*p)->ice_getIdentity() != _master->ice_getIdentity())
                 {
                     _replicas.insert((*p)->ice_getIdentity());
-                    NodeSessionKeepAliveThreadPtr session = addReplicaSession(*p);
-                    session->tryCreateSession(false);
-                    sessions.push_back(session);
+
+                    if(_sessions.find((*p)->ice_getIdentity()) == _sessions.end())
+                    {
+                        NodeSessionKeepAliveThreadPtr session = addReplicaSession(*p);
+                        session->tryCreateSession();
+                        sessions.push_back(session);
+                    }
+                    else
+                    {
+                        addReplicaSession(*p); // Update the session
+                    }
                 }
             }
         }
@@ -664,7 +672,7 @@ NodeSessionManager::createdSession(const NodeSessionPrx& session)
         {
             break;
         }
-        (*p)->tryCreateSession(true, timeout);
+        (*p)->waitTryCreateSession(timeout);
     }
 }
 
diff --git a/cpp/src/IceGrid/NodeSessionManager.h b/cpp/src/IceGrid/NodeSessionManager.h
index 7abe10554cf..bd8552ddb8e 100644
--- a/cpp/src/IceGrid/NodeSessionManager.h
+++ b/cpp/src/IceGrid/NodeSessionManager.h
@@ -25,11 +25,13 @@ namespace IceGrid
 class NodeI;
 typedef IceUtil::Handle<NodeI> NodeIPtr;
 
+class NodeSessionManager;
+
 class NodeSessionKeepAliveThread : public SessionKeepAliveThread<NodeSessionPrx>
 {
 public:
 
-    NodeSessionKeepAliveThread(const InternalRegistryPrx&, const NodeIPtr&, const std::vector<QueryPrx>&);
+    NodeSessionKeepAliveThread(const InternalRegistryPrx&, const NodeIPtr&, NodeSessionManager&);
 
     virtual NodeSessionPrx createSession(InternalRegistryPrx&, IceUtil::Time&);
     virtual void destroySession(const NodeSessionPrx&);
@@ -43,7 +45,7 @@ protected:
 
     const NodeIPtr _node;
     const std::string _name;
-    const std::vector<QueryPrx> _queryObjects;
+    NodeSessionManager& _manager;
 };
 typedef IceUtil::Handle<NodeSessionKeepAliveThread> NodeSessionKeepAliveThreadPtr;
 
@@ -51,7 +53,7 @@ class NodeSessionManager : public SessionManager
 {
 public:
 
-    NodeSessionManager(const Ice::CommunicatorPtr&);
+    NodeSessionManager(const Ice::CommunicatorPtr&, const std::string&);
     
     void create(const NodeIPtr&);
     void create(const InternalRegistryPrx&);
@@ -65,6 +67,7 @@ public:
     void replicaRemoved(const InternalRegistryPrx&);
 
     NodeSessionPrx getMasterNodeSession() const { return _thread->getSession(); }
+    std::vector<IceGrid::QueryPrx> getQueryObjects() { return findAllQueryObjects(true); }
 
 private:
 
@@ -84,9 +87,7 @@ private:
     {
     public:
 
-        Thread(NodeSessionManager& manager) : 
-            NodeSessionKeepAliveThread(manager._master, manager._node, manager._queryObjects),
-            _manager(manager)
+        Thread(NodeSessionManager& manager) : NodeSessionKeepAliveThread(manager._master, manager._node, manager)
         {
         }
 
@@ -113,10 +114,6 @@ private:
             _manager.reapReplicas();
             return alive;
         }
-
-    private:
-        
-        NodeSessionManager& _manager;
     };
     typedef IceUtil::Handle<Thread> ThreadPtr;
     friend class Thread;
diff --git a/cpp/src/IceGrid/RegistryI.cpp b/cpp/src/IceGrid/RegistryI.cpp
index 8ab2ed0bd92..071942cd8f5 100644
--- a/cpp/src/IceGrid/RegistryI.cpp
+++ b/cpp/src/IceGrid/RegistryI.cpp
@@ -205,7 +205,6 @@ RegistryI::RegistryI(const CommunicatorPtr& communicator,
     _nowarn(nowarn),
     _readonly(readonly),
     _initFromReplica(initFromReplica),
-    _session(communicator),
     _platform("IceGrid.Registry", communicator, traceLevels)
 {
 }
@@ -337,36 +336,38 @@ RegistryI::startImpl()
 
     properties->setProperty("Ice.ACM.Server.Close", "3"); // Close on invocation and idle.
     
-    if(!_master && properties->getProperty("Ice.Default.Locator").empty() && 
-       properties->getProperty("Ice.Default.Locator").empty())
+    if(!_master && !_communicator->getDefaultLocator())
     {
         Error out(_communicator->getLogger());
         out << "property `Ice.Default.Locator' is not set";
         return false;
     }
+    else if(_master)
+    {
+        _communicator->setDefaultLocator(0); // Clear the default locator in case it's set.
+    }
 
     //
     // Get the instance name
     //
-    if(_master)
+    _instanceName = properties->getProperty("IceGrid.InstanceName");    
+    if(_instanceName.empty())
     {
-        _instanceName = properties->getProperty("IceGrid.InstanceName");    
-        if(_instanceName.empty())
-        {
-            if(_communicator->getDefaultLocator())
-            {
-                _instanceName = _communicator->getDefaultLocator()->ice_getIdentity().category;
-            }
-            else
-            {
-                _instanceName = "IceGrid";
-            }
-        }
+        _instanceName = properties->getProperty("IceGridDiscovery.InstanceName");
     }
-    else
+    if(_instanceName.empty() && _communicator->getDefaultLocator())
     {
         _instanceName = _communicator->getDefaultLocator()->ice_getIdentity().category;
     }
+    if(_instanceName.empty())
+    {
+        _instanceName = "IceGrid";
+    }
+
+    //
+    // Create the replica session manager
+    //
+    _session.reset(new ReplicaSessionManager(_communicator, _instanceName));
 
     //
     // Create the registry database.
@@ -485,7 +486,7 @@ RegistryI::startImpl()
         if(!proxy)
         {
             id.name = "InternalRegistry-" + (_initFromReplica.empty() ? "Master" : _initFromReplica);
-            proxy = _session.findInternalRegistryForReplica(id);
+            proxy = _session->findInternalRegistryForReplica(id);
         }
 
         if(!proxy)
@@ -550,8 +551,8 @@ RegistryI::startImpl()
     else
     {
         InternalReplicaInfoPtr info = _platform.getInternalReplicaInfo();
-        _session.create(_replicaName, info, _database, _wellKnownObjects, internalRegistry);
-        registerNodes(internalRegistry, _session.getNodes(nodes));
+        _session->create(_replicaName, info, _database, _wellKnownObjects, internalRegistry);
+        registerNodes(internalRegistry, _session->getNodes(nodes));
     }
 
     _serverAdapter = _communicator->createObjectAdapter("IceGrid.Registry.Server");
@@ -600,7 +601,7 @@ RegistryI::startImpl()
     }
     else
     {
-        _session.registerAllWellKnownObjects();
+        _session->registerAllWellKnownObjects();
     }
 
     //
@@ -685,7 +686,7 @@ RegistryI::setupLocatorRegistry()
     Identity locatorRegId;
     locatorRegId.category = _instanceName;
     locatorRegId.name = "LocatorRegistry-" + _replicaName;
-    ObjectPrx obj = _serverAdapter->add(new LocatorRegistryI(_database, dynReg, _master, _session), locatorRegId);
+    ObjectPrx obj = _serverAdapter->add(new LocatorRegistryI(_database, dynReg, _master, *_session), locatorRegId);
     return LocatorRegistryPrx::uncheckedCast(obj);
 }
 
@@ -738,7 +739,7 @@ RegistryI::setupInternalRegistry()
     internalRegistryId.category = _instanceName;
     internalRegistryId.name = "InternalRegistry-" + _replicaName;
     assert(_reaper);
-    ObjectPtr internalRegistry = new InternalRegistryI(this, _database, _reaper, _wellKnownObjects, _session);
+    ObjectPtr internalRegistry = new InternalRegistryI(this, _database, _reaper, _wellKnownObjects, *_session);
     Ice::ObjectPrx proxy = _registryAdapter->add(internalRegistry, internalRegistryId);
     _wellKnownObjects->add(proxy, InternalRegistry::ice_staticId());
 
@@ -903,8 +904,11 @@ RegistryI::setupAdminSessionFactory(const Ice::ObjectPtr& router, const IceGrid:
 void
 RegistryI::stop()
 {
-    _session.destroy();
-    
+    if(_session.get())
+    {
+        _session->destroy();
+    }
+
     //
     // We destroy the topics before to shutdown the communicator to
     // ensure that there will be no more invocations on IceStorm once
@@ -1233,6 +1237,12 @@ RegistryI::createAdminCallbackProxy(const Identity& id) const
     return _serverAdapter->createProxy(id);
 }
 
+Ice::LocatorPrx 
+RegistryI::getLocator()
+{
+    return _wellKnownObjects->getLocator();
+}
+
 Glacier2::PermissionsVerifierPrx
 RegistryI::getPermissionsVerifier(const IceGrid::LocatorPrx& locator,
                                   const string& verifierProperty,
diff --git a/cpp/src/IceGrid/RegistryI.h b/cpp/src/IceGrid/RegistryI.h
index 75da1fa1259..e4a303e533b 100644
--- a/cpp/src/IceGrid/RegistryI.h
+++ b/cpp/src/IceGrid/RegistryI.h
@@ -79,6 +79,8 @@ public:
 
     const Ice::ObjectAdapterPtr& getRegistryAdapter() { return _registryAdapter; }
 
+    Ice::LocatorPrx getLocator();
+
 private:
 
     Ice::LocatorRegistryPrx setupLocatorRegistry(); 
@@ -117,7 +119,7 @@ private:
     IceUtil::TimerPtr _timer;
     SessionServantManagerPtr _servantManager;
     int _sessionTimeout;
-    ReplicaSessionManager _session;
+    IceUtil::UniquePtr<ReplicaSessionManager> _session;
     mutable PlatformInfo _platform;
         
     Glacier2::PermissionsVerifierPrx _nullPermissionsVerifier;
diff --git a/cpp/src/IceGrid/ReplicaSessionManager.cpp b/cpp/src/IceGrid/ReplicaSessionManager.cpp
index b053b21a988..fbce90c0816 100644
--- a/cpp/src/IceGrid/ReplicaSessionManager.cpp
+++ b/cpp/src/IceGrid/ReplicaSessionManager.cpp
@@ -282,7 +282,8 @@ private:
 
 };
 
-ReplicaSessionManager::ReplicaSessionManager(const Ice::CommunicatorPtr& communicator) : SessionManager(communicator) 
+ReplicaSessionManager::ReplicaSessionManager(const Ice::CommunicatorPtr& communicator, const string& instanceName) :
+    SessionManager(communicator, instanceName) 
 {
 }
 
@@ -309,6 +310,7 @@ ReplicaSessionManager::create(const string& name,
     }    
 
     _thread->tryCreateSession();
+    _thread->waitTryCreateSession();
 }
 
 void
@@ -330,6 +332,7 @@ ReplicaSessionManager::create(const InternalRegistryPrx& replica)
 
     _thread->setRegistry(replica);
     _thread->tryCreateSession();
+    _thread->waitTryCreateSession();
 }
 
 NodePrxSeq
@@ -412,7 +415,7 @@ IceGrid::InternalRegistryPrx
 ReplicaSessionManager::findInternalRegistryForReplica(const Ice::Identity& id)
 {
     vector<Ice::AsyncResultPtr> results;
-    vector<QueryPrx> queryObjects = findAllQueryObjects();
+    vector<QueryPrx> queryObjects = findAllQueryObjects(true);
     for(vector<QueryPrx>::const_iterator q = queryObjects.begin(); q != queryObjects.end(); ++q)
     {
         results.push_back((*q)->begin_findObjectById(id));
@@ -489,7 +492,7 @@ ReplicaSessionManager::createSession(InternalRegistryPrx& registry, IceUtil::Tim
         if(!session)
         {
             vector<Ice::AsyncResultPtr> results;
-            vector<QueryPrx> queryObjects = findAllQueryObjects();
+            vector<QueryPrx> queryObjects = findAllQueryObjects(false);
             for(vector<QueryPrx>::const_iterator q = queryObjects.begin(); q != queryObjects.end(); ++q)
             {
                 results.push_back((*q)->begin_findObjectById(registry->ice_getIdentity()));
diff --git a/cpp/src/IceGrid/ReplicaSessionManager.h b/cpp/src/IceGrid/ReplicaSessionManager.h
index 8e5c7308dce..31a9de77ae2 100644
--- a/cpp/src/IceGrid/ReplicaSessionManager.h
+++ b/cpp/src/IceGrid/ReplicaSessionManager.h
@@ -69,7 +69,7 @@ public:
     };
     typedef IceUtil::Handle<Thread> ThreadPtr;
 
-    ReplicaSessionManager(const Ice::CommunicatorPtr&);
+    ReplicaSessionManager(const Ice::CommunicatorPtr&, const std::string&);
     void create(const std::string&, const InternalReplicaInfoPtr&, const DatabasePtr&, 
                 const WellKnownObjectsManagerPtr&, const InternalRegistryPrx&);
     void create(const InternalRegistryPrx&);
diff --git a/cpp/src/IceGrid/ServerI.cpp b/cpp/src/IceGrid/ServerI.cpp
index 33df2ed49e1..0234020b553 100644
--- a/cpp/src/IceGrid/ServerI.cpp
+++ b/cpp/src/IceGrid/ServerI.cpp
@@ -3174,9 +3174,20 @@ ServerI::getProperties(const InternalServerDescriptorPtr& desc)
         {
             if(getProperty(p->second, "Ice.Default.Locator").empty())
             {
-                p->second.push_back(
-                    createProperty("Ice.Default.Locator",
-                                   _node->getCommunicator()->getProperties()->getProperty("Ice.Default.Locator")));
+                Ice::PropertiesPtr properties = _node->getCommunicator()->getProperties();
+
+                string locator = properties->getProperty("Ice.Default.Locator");
+                if(!locator.empty())
+                {
+                    p->second.push_back(createProperty("Ice.Default.Locator", locator));
+                }
+
+                string discoveryPlugin = properties->getProperty("Ice.Plugin.IceGridDiscovery");
+                if(!discoveryPlugin.empty())
+                {
+                    p->second.push_back(createProperty("Ice.Plugin.IceGridDiscovery", discoveryPlugin));
+                    p->second.push_back(createProperty("IceGridDiscovery.InstanceName", _node->getInstanceName()));
+                }
             }
             
             if(!overrides.empty())
diff --git a/cpp/src/IceGrid/SessionManager.cpp b/cpp/src/IceGrid/SessionManager.cpp
index 826195ed4ac..dcc4d500c2f 100644
--- a/cpp/src/IceGrid/SessionManager.cpp
+++ b/cpp/src/IceGrid/SessionManager.cpp
@@ -13,26 +13,14 @@
 using namespace std;
 using namespace IceGrid;
 
-SessionManager::SessionManager(const Ice::CommunicatorPtr& communicator) : _communicator(communicator)
+SessionManager::SessionManager(const Ice::CommunicatorPtr& communicator, const string& instanceName) :
+    _communicator(communicator), _instanceName(instanceName)
 {
-    if(communicator->getDefaultLocator())
+    Ice::LocatorPrx prx = communicator->getDefaultLocator();
+    if(prx)
     {
-        Ice::ObjectPrx prx = communicator->getDefaultLocator();
-
-        //
-        // Derive the query objects from the locator proxy endpoints.
-        //
-        Ice::EndpointSeq endpoints = prx->ice_getEndpoints();
-        Ice::Identity id = prx->ice_getIdentity();
-        id.name = "Query";
-        QueryPrx query = QueryPrx::uncheckedCast(prx->ice_identity(id));
-        for(Ice::EndpointSeq::const_iterator p = endpoints.begin(); p != endpoints.end(); ++p)
-        {
-            Ice::EndpointSeq singleEndpoint;
-            singleEndpoint.push_back(*p);
-            _queryObjects.push_back(QueryPrx::uncheckedCast(query->ice_endpoints(singleEndpoint)));
-        }
-
+        Ice::Identity id;
+        id.category = instanceName;
         id.name = "InternalRegistry-Master";
         _master = InternalRegistryPrx::uncheckedCast(prx->ice_identity(id)->ice_endpoints(Ice::EndpointSeq()));
     }
@@ -43,20 +31,68 @@ SessionManager::~SessionManager()
 }
 
 vector<QueryPrx>
-SessionManager::findAllQueryObjects()
+SessionManager::findAllQueryObjects(bool cached)
 {
-    vector<QueryPrx> queryObjects = _queryObjects;
-    for(vector<QueryPrx>::const_iterator q = _queryObjects.begin(); q != _queryObjects.end(); ++q)
+    vector<QueryPrx> queryObjects;
     {
-        Ice::ConnectionPtr connection = (*q)->ice_getCachedConnection();
-        if(connection)
+        Lock sync(*this);
+        if(cached && !_queryObjects.empty())
         {
-            try
+            return _queryObjects;
+        }
+        queryObjects = _queryObjects;
+    }
+
+    if(!cached)
+    {
+        for(vector<QueryPrx>::const_iterator q = queryObjects.begin(); q != queryObjects.end(); ++q)
+        {
+            Ice::ConnectionPtr connection = (*q)->ice_getCachedConnection();
+            if(connection)
+            {
+                try
+                {
+                    connection->close(false);
+                }
+                catch(const Ice::LocalException&)
+                {
+                }
+            }
+        }
+        queryObjects.clear();
+    }
+
+    if(queryObjects.empty())
+    {
+        Ice::LocatorPrx locator = _communicator->getDefaultLocator();
+        if(locator)
+        {
+            Ice::Identity id;
+            id.category = _instanceName;
+            id.name = "Query";
+            QueryPrx query = QueryPrx::uncheckedCast(locator->ice_identity(id));
+            Ice::EndpointSeq endpoints = query->ice_getEndpoints();
+            if(endpoints.empty())
             {
-                connection->close(false);
+                try
+                {
+                    Ice::ObjectPrx r = locator->findObjectById(id);
+                    if(r)
+                    {
+                        endpoints = r->ice_getEndpoints();
+                    }
+                }
+                catch(const Ice::Exception&)
+                {
+                        // Ignore.
+                }
             }
-            catch(const Ice::LocalException&)
+            
+            for(Ice::EndpointSeq::const_iterator p = endpoints.begin(); p != endpoints.end(); ++p)
             {
+                Ice::EndpointSeq singleEndpoint;
+                singleEndpoint.push_back(*p);
+                queryObjects.push_back(QueryPrx::uncheckedCast(query->ice_endpoints(singleEndpoint)));
             }
         }
     }
@@ -103,5 +139,8 @@ SessionManager::findAllQueryObjects()
         }
     }
     while(proxies.size() != previousSize);
-    return queryObjects;
+    
+    Lock sync(*this);
+    _queryObjects.swap(queryObjects);
+    return _queryObjects;
 }
diff --git a/cpp/src/IceGrid/SessionManager.h b/cpp/src/IceGrid/SessionManager.h
index e1d3d6e90de..2ff28178032 100644
--- a/cpp/src/IceGrid/SessionManager.h
+++ b/cpp/src/IceGrid/SessionManager.h
@@ -192,8 +192,8 @@ public:
         return _state != Destroyed;
     }
 
-    virtual void
-    tryCreateSession(bool waitForTry = true, const IceUtil::Time& timeout = IceUtil::Time())
+    void
+    tryCreateSession()
     {
         {
             Lock sync(*this);
@@ -212,23 +212,24 @@ public:
             }
             notifyAll();
         }
+    }
 
-        if(waitForTry)
+    void
+    waitTryCreateSession(const IceUtil::Time& timeout = IceUtil::Time())
+    {
+        Lock sync(*this);
+        // Wait until the action is executed and the state changes.
+        while(_nextAction == Connect || _nextAction == KeepAlive || _state == InProgress)
         {
-            Lock sync(*this);
-            // Wait until the action is executed and the state changes.
-            while(_nextAction == Connect || _nextAction == KeepAlive || _state == InProgress)
+            if(timeout == IceUtil::Time())
             {
-                if(timeout == IceUtil::Time())
-                {
-                    wait();
-                }
-                else
+                wait();
+            }
+            else
+            {
+                if(!timedWait(timeout))
                 {
-                    if(!timedWait(timeout))
-                    {
-                        break;
-                    }
+                    break;
                 }
             }
         }
@@ -320,16 +321,17 @@ class SessionManager : public IceUtil::Monitor<IceUtil::Mutex>
 {
 public:
 
-    SessionManager(const Ice::CommunicatorPtr&);
+    SessionManager(const Ice::CommunicatorPtr&, const std::string&);
     virtual ~SessionManager();
 
     virtual bool isDestroyed() = 0;
 
 protected:
 
-    std::vector<IceGrid::QueryPrx> findAllQueryObjects();
+    std::vector<IceGrid::QueryPrx> findAllQueryObjects(bool);
 
     Ice::CommunicatorPtr _communicator;
+    std::string _instanceName;
     InternalRegistryPrx _master;
     std::vector<IceGrid::QueryPrx> _queryObjects;
 };
diff --git a/cpp/src/IceGridLib/DiscoveryPluginI.cpp b/cpp/src/IceGridLib/DiscoveryPluginI.cpp
index 02b9327da37..521bda66f22 100644
--- a/cpp/src/IceGridLib/DiscoveryPluginI.cpp
+++ b/cpp/src/IceGridLib/DiscoveryPluginI.cpp
@@ -29,34 +29,47 @@ class Request : public IceUtil::Shared
 {
 public:
 
-    Request(LocatorI* locator) : _locator(locator)
+    Request(LocatorI* locator, 
+            const string& operation,
+            ::Ice::OperationMode mode, 
+            const pair<const Ice::Byte*, const Ice::Byte*>& inParams, 
+            const ::Ice::Context& ctx,
+            const Ice::AMD_Object_ice_invokePtr& amdCB) :
+        _locator(locator), 
+        _operation(operation),
+        _mode(mode),
+        _context(ctx),
+        _inParams(inParams.first, inParams.second),
+        _amdCB(amdCB)
     {
     }
 
-    virtual void invoke(const Ice::LocatorPrx&) = 0;
-    virtual void response(const Ice::ObjectPrx&) = 0;
+    void invoke(const Ice::LocatorPrx&);
+    void response(const bool, const pair<const Ice::Byte*, const Ice::Byte*>&);
+    void exception(const Ice::Exception&);
 
 protected:
 
     LocatorI* _locator;
+    const string _operation;
+    const Ice::OperationMode _mode;
+    const Ice::Context _context;
+    const Ice::ByteSeq _inParams;
+    const Ice::AMD_Object_ice_invokePtr _amdCB;
+
     Ice::LocatorPrx _locatorPrx;
 };
 typedef IceUtil::Handle<Request> RequestPtr;
 
-class LocatorI : public Ice::Locator, private IceUtil::TimerTask, private IceUtil::Monitor<IceUtil::Mutex>
+class LocatorI : public Ice::BlobjectArrayAsync, private IceUtil::TimerTask, private IceUtil::Monitor<IceUtil::Mutex>
 {
 public:
 
-    LocatorI(const LookupPrx&, const Ice::PropertiesPtr&);
+    LocatorI(const LookupPrx&, const Ice::PropertiesPtr&, const string&, const LocatorPrx&);
     void setLookupReply(const LookupReplyPrx&);
 
-    virtual void findObjectById_async(const Ice::AMD_Locator_findObjectByIdPtr&, const Ice::Identity&,
-                                      const Ice::Current&) const;
-
-    virtual void findAdapterById_async(const Ice::AMD_Locator_findAdapterByIdPtr&, const string&,
-                                       const Ice::Current&) const;
-
-    virtual Ice::LocatorRegistryPrx getRegistry(const Ice::Current&) const;
+    virtual void ice_invoke_async(const Ice::AMD_Object_ice_invokePtr&, const pair<const Ice::Byte*, const Ice::Byte*>&,
+                                  const Ice::Current&);
 
     void foundLocator(const LocatorPrx&);
     void invoke(const Ice::LocatorPrx&, const RequestPtr&);
@@ -64,18 +77,20 @@ public:
 private:
 
     virtual void runTimerTask();
-    void queueRequest(const RequestPtr&);
 
     const LookupPrx _lookup;
     const IceUtil::Time _timeout;
     const int _retryCount;
+    const IceUtil::Time _retryDelay;
     const IceUtil::TimerPtr _timer;
 
     string _instanceName;
     bool _warned;
     LookupReplyPrx _lookupReply;
     Ice::LocatorPrx _locator;
+    IceGrid::LocatorPrx _voidLocator;
 
+    IceUtil::Time _nextRetry;
     int _pendingRetryCount;
     vector<RequestPtr> _pendingRequests;
 };
@@ -96,52 +111,46 @@ private:
     const LocatorIPtr _locator;
 };
 
-class ObjectRequest : public Request
+//
+// The void locator implementation below is used when no locator is found.
+//
+class VoidLocatorI : public IceGrid::Locator
 {
 public:
-
-    ObjectRequest(LocatorI* locator, const Ice::Identity& id, const Ice::AMD_Locator_findObjectByIdPtr& amdCB) :
-        Request(locator), _id(id), _amdCB(amdCB)
+    
+    virtual void 
+    findObjectById_async(const Ice::AMD_Locator_findObjectByIdPtr& amdCB, 
+                         const Ice::Identity&, 
+                         const Ice::Current&) const
     {
+        amdCB->ice_response(0);
     }
 
-    virtual void invoke(const Ice::LocatorPrx&);
-    virtual void response(const Ice::ObjectPrx&);
-
-    void
-    exception(const Ice::Exception&)
+    virtual void 
+    findAdapterById_async(const Ice::AMD_Locator_findAdapterByIdPtr& amdCB,
+                          const string&, 
+                          const Ice::Current&) const
     {
-        _locator->invoke(_locatorPrx, this); // Retry with new locator proxy
+        amdCB->ice_response(0);
     }
 
-private:
-
-    const Ice::Identity _id;
-    Ice::AMD_Locator_findObjectByIdPtr _amdCB;
-};
-
-class AdapterRequest : public Request
-{
-public:
-
-    AdapterRequest(LocatorI* locator, const string& adapterId, const Ice::AMD_Locator_findAdapterByIdPtr& amdCB) :
-        Request(locator), _adapterId(adapterId), _amdCB(amdCB)
+    virtual Ice::LocatorRegistryPrx 
+    getRegistry(const Ice::Current&) const
     {
+        return 0;
     }
 
-    virtual void invoke(const Ice::LocatorPrx&);
-    virtual void response(const Ice::ObjectPrx&);
-
-    void
-    exception(const Ice::Exception&)
+    virtual IceGrid::RegistryPrx 
+    getLocalRegistry(const Ice::Current&) const
     {
-        _locator->invoke(_locatorPrx, this); // Retry with new locator proxy.
+        return 0;
     }
 
-private:
-
-    const string _adapterId;
-    const Ice::AMD_Locator_findAdapterByIdPtr _amdCB;
+    virtual IceGrid::QueryPrx 
+    getLocalQuery(const Ice::Current&) const
+    {
+        return 0;
+    }
 };
 
 }
@@ -231,8 +240,14 @@ DiscoveryPluginI::initialize()
         throw Ice::PluginInitializationException(__FILE__, __LINE__, os.str());
     }
 
-    LocatorIPtr locator = new LocatorI(LookupPrx::uncheckedCast(lookupPrx), properties);
-    _communicator->setDefaultLocator(Ice::LocatorPrx::uncheckedCast(_locatorAdapter->addWithUUID(locator)));
+    LocatorPrx voidLocator = LocatorPrx::uncheckedCast(_locatorAdapter->addWithUUID(new VoidLocatorI()));
+
+    string instanceName = properties->getProperty("IceGridDiscovery.InstanceName");
+    Ice::Identity id;
+    id.name = "Locator";
+    id.category = !instanceName.empty() ? instanceName : IceUtil::generateUUID();
+    LocatorIPtr locator = new LocatorI(LookupPrx::uncheckedCast(lookupPrx), properties, instanceName, voidLocator);
+    _communicator->setDefaultLocator(Ice::LocatorPrx::uncheckedCast(_locatorAdapter->add(locator, id)));
 
     Ice::ObjectPrx lookupReply = _replyAdapter->addWithUUID(new LookupReplyI(locator))->ice_datagram();
     locator->setLookupReply(LookupReplyPrx::uncheckedCast(lookupReply));
@@ -249,43 +264,38 @@ DiscoveryPluginI::destroy()
 }
 
 void
-AdapterRequest::invoke(const Ice::LocatorPrx& l)
+Request::invoke(const Ice::LocatorPrx& l)
 {
     _locatorPrx = l;
-    l->begin_findAdapterById(_adapterId, Ice::newCallback_Locator_findAdapterById(this,
-                                                                                  &AdapterRequest::response,
-                                                                                  &AdapterRequest::exception));
-}
-
-void
-AdapterRequest::response(const Ice::ObjectPrx& prx)
-{
-    _amdCB->ice_response(prx);
+    l->begin_ice_invoke(_operation, _mode, _inParams, _context,
+                        Ice::newCallback_Object_ice_invoke(this, &Request::response, &Request::exception));
 }
 
 void
-ObjectRequest::invoke(const Ice::LocatorPrx& l)
+Request::response(bool ok, const pair<const Ice::Byte*, const Ice::Byte*>& outParams)
 {
-    _locatorPrx = l;
-    l->begin_findObjectById(_id, Ice::newCallback_Locator_findObjectById(this,
-                                                                         &ObjectRequest::response,
-                                                                         &ObjectRequest::exception));
+    _amdCB->ice_response(ok, outParams);
 }
 
 void
-ObjectRequest::response(const Ice::ObjectPrx& prx)
+Request::exception(const Ice::Exception& ex)
 {
-    _amdCB->ice_response(prx);
+    _locator->invoke(_locatorPrx, this); // Retry with new locator proxy
 }
 
-LocatorI::LocatorI(const LookupPrx& lookup, const Ice::PropertiesPtr& properties) :
+LocatorI::LocatorI(const LookupPrx& lookup, 
+                   const Ice::PropertiesPtr& props, 
+                   const string& instanceName,
+                   const IceGrid::LocatorPrx& voidLocator) :
     _lookup(lookup),
-    _timeout(IceUtil::Time::milliSeconds(properties->getPropertyAsIntWithDefault("IceGridDiscovery.Timeout", 300))),
-    _retryCount(properties->getPropertyAsIntWithDefault("IceGridDiscovery.RetryCount", 3)),
+    _timeout(IceUtil::Time::milliSeconds(props->getPropertyAsIntWithDefault("IceGridDiscovery.Timeout", 300))),
+    _retryCount(props->getPropertyAsIntWithDefault("IceGridDiscovery.RetryCount", 3)),
+    _retryDelay(IceUtil::Time::milliSeconds(props->getPropertyAsIntWithDefault("IceGridDiscovery.RetryDelay", 2000))),
     _timer(IceInternal::getInstanceTimer(lookup->ice_getCommunicator())),
-    _instanceName(properties->getProperty("IceGridDiscovery.InstanceName")),
+    _instanceName(instanceName),
     _warned(false),
     _locator(lookup->ice_getCommunicator()->getDefaultLocator()),
+    _voidLocator(voidLocator),
     _pendingRetryCount(0)
 {
 }
@@ -297,45 +307,18 @@ LocatorI::setLookupReply(const LookupReplyPrx& lookupReply)
 }
 
 void
-LocatorI::findObjectById_async(const Ice::AMD_Locator_findObjectByIdPtr& amdCB,
-                               const Ice::Identity& id,
-                               const Ice::Current&) const
+LocatorI::ice_invoke_async(const Ice::AMD_Object_ice_invokePtr& amdCB, 
+                           const pair<const Ice::Byte*, const Ice::Byte*>& inParams,
+                           const Ice::Current& current)
 {
-    const_cast<LocatorI*>(this)->invoke(0, new ObjectRequest(const_cast<LocatorI*>(this), id, amdCB));
-}
-
-void
-LocatorI::findAdapterById_async(const Ice::AMD_Locator_findAdapterByIdPtr& amdCB,
-                                const string& adapterId,
-                                const Ice::Current&) const
-{
-    const_cast<LocatorI*>(this)->invoke(0, new AdapterRequest(const_cast<LocatorI*>(this), adapterId, amdCB));
-}
-
-Ice::LocatorRegistryPrx
-LocatorI::getRegistry(const Ice::Current&) const
-{
-    Ice::LocatorPrx locator;
-    {
-        Lock sync(*this);
-        if(!_locator)
-        {
-            const_cast<LocatorI*>(this)->queueRequest(0); // Search for locator if not already doing so.
-            while(_pendingRetryCount > 0)
-            {
-                wait();
-            }
-        }
-        locator = _locator;
-    }
-    return locator ? locator->getRegistry() : Ice::LocatorRegistryPrx();
+    invoke(0, new Request(this, current.operation, current.mode, inParams, current.ctx, amdCB));
 }
 
 void
 LocatorI::foundLocator(const LocatorPrx& locator)
 {
     Lock sync(*this);
-    if(!locator)
+    if(!locator || (!_instanceName.empty() && locator->ice_getIdentity().category != _instanceName))
     {
         return;
     }
@@ -401,7 +384,7 @@ LocatorI::foundLocator(const LocatorPrx& locator)
         _locator = locator;
         if(_instanceName.empty())
         {
-            _instanceName = _locator->ice_getIdentity().category;
+            _instanceName = _locator->ice_getIdentity().category; // Stick to the first discovered locator.
         }
     }
 
@@ -413,7 +396,6 @@ LocatorI::foundLocator(const LocatorPrx& locator)
         (*p)->invoke(_locator);
     }
     _pendingRequests.clear();
-    notifyAll();
 }
 
 void
@@ -424,10 +406,22 @@ LocatorI::invoke(const Ice::LocatorPrx& locator, const RequestPtr& request)
     {
         request->invoke(_locator);
     }
+    else if(IceUtil::Time::now() < _nextRetry)
+    {
+        request->invoke(_voidLocator); // Don't retry to find a locator before the retry delay expires
+    }
     else
     {
         _locator = 0;
-        queueRequest(request);
+
+        _pendingRequests.push_back(request);
+
+        if(_pendingRetryCount == 0) // No request in progress
+        {
+            _pendingRetryCount = _retryCount;
+            _lookup->begin_findLocator(_instanceName, _lookupReply); // Send multicast request.
+            _timer->schedule(this, _timeout);
+        }
     }
 }
 
@@ -445,26 +439,10 @@ LocatorI::runTimerTask()
         assert(!_pendingRequests.empty());
         for(vector<RequestPtr>::const_iterator p = _pendingRequests.begin(); p != _pendingRequests.end(); ++p)
         {
-            (*p)->response(0);
+            (*p)->invoke(_voidLocator); // Send pending requests on void locator.
         }
         _pendingRequests.clear();
-        notifyAll();
-    }
-}
-
-void
-LocatorI::queueRequest(const RequestPtr& request)
-{
-    if(request)
-    {
-        _pendingRequests.push_back(request);
-    }
-
-    if(_pendingRetryCount == 0) // No request in progress
-    {
-        _pendingRetryCount = _retryCount;
-        _lookup->begin_findLocator(_instanceName, _lookupReply); // Send multicast request.
-        _timer->schedule(this, _timeout);
+        _nextRetry = IceUtil::Time::now() + _retryDelay; // Only retry when the retry delay expires
     }
 }
 
diff --git a/cpp/test/IceGrid/simple/AllTests.cpp b/cpp/test/IceGrid/simple/AllTests.cpp
index 5ee95f3dad4..184e18adac7 100644
--- a/cpp/test/IceGrid/simple/AllTests.cpp
+++ b/cpp/test/IceGrid/simple/AllTests.cpp
@@ -50,14 +50,72 @@ allTests(const Ice::CommunicatorPtr& communicator)
 
     cout << "testing discovery... " << flush;
     {
+        // Add test well-known object
+        IceGrid::RegistryPrx registry = IceGrid::RegistryPrx::checkedCast(
+            communicator->stringToProxy(communicator->getDefaultLocator()->ice_getIdentity().category + "/Registry"));
+        test(registry);
+
+        IceGrid::AdminSessionPrx session = registry->createAdminSession("foo", "bar");
+        session->getAdmin()->addObjectWithType(base, "::Test");
+        session->destroy();
+
+        //
+        // Ensure the IceGrid discovery locator can discover the
+        // registries and make sure locator requests are forwarded.
+        //
         Ice::InitializationData initData;
         initData.properties = communicator->getProperties()->clone();
         initData.properties->setProperty("Ice.Default.Locator", "");
         initData.properties->setProperty("Ice.Plugin.IceGridDiscovery", "IceGrid:createIceGridDiscovery");
+        initData.properties->setProperty("AdapterForDiscoveryTest.AdapterId", "discoveryAdapter");
+        initData.properties->setProperty("AdapterForDiscoveryTest.Endpoints", "default");
 
         Ice::CommunicatorPtr com = Ice::initialize(initData);
         test(com->getDefaultLocator());
         com->stringToProxy("test @ TestAdapter")->ice_ping();
+        com->stringToProxy("test")->ice_ping();
+
+        test(com->getDefaultLocator()->getRegistry());
+        test(IceGrid::LocatorPrx::uncheckedCast(com->getDefaultLocator())->getLocalRegistry());
+        test(IceGrid::LocatorPrx::uncheckedCast(com->getDefaultLocator())->getLocalQuery());
+
+        Ice::ObjectAdapterPtr adapter = com->createObjectAdapter("AdapterForDiscoveryTest");
+        adapter->activate();
+        adapter->deactivate();
+
+        com->destroy();
+
+        //
+        // Now, ensure that the IceGrid discovery locator correctly
+        // handles failure to find a locator.
+        // 
+        initData.properties->setProperty("IceGridDiscovery.InstanceName", "unknown");
+        initData.properties->setProperty("IceGridDiscovery.RetryCount", "1");
+        initData.properties->setProperty("IceGridDiscovery.Timeout", "100");
+        com = Ice::initialize(initData);
+        test(com->getDefaultLocator());
+        try
+        {
+            com->stringToProxy("test @ TestAdapter")->ice_ping();
+        }
+        catch(const Ice::NoEndpointException&)
+        {
+        }
+        try
+        {
+            com->stringToProxy("test")->ice_ping();
+        }
+        catch(const Ice::NoEndpointException&)
+        {
+        }
+        test(!com->getDefaultLocator()->getRegistry());
+        test(!IceGrid::LocatorPrx::uncheckedCast(com->getDefaultLocator())->getLocalRegistry());
+        test(!IceGrid::LocatorPrx::uncheckedCast(com->getDefaultLocator())->getLocalQuery());
+
+        adapter = com->createObjectAdapter("AdapterForDiscoveryTest");
+        adapter->activate();
+        adapter->deactivate();
+
         com->destroy();
     }
     cout << "ok" << endl;
diff --git a/cpp/test/IceGrid/simple/run.py b/cpp/test/IceGrid/simple/run.py
index 80f594895d9..14478af1931 100755
--- a/cpp/test/IceGrid/simple/run.py
+++ b/cpp/test/IceGrid/simple/run.py
@@ -20,6 +20,9 @@ if len(path) == 0:
 sys.path.append(os.path.join(path[0], "scripts"))
 import TestUtil, IceGridAdmin
 
+# Test IceGrid discovery with multiple replicas
+IceGridAdmin.nreplicas=2
+
 #
 # Test client/server without on demand activation.
 #