Reverts changes to component application and adds further client migration handling hookup

Signed-off-by: kberg-amzn <karlberg@amazon.com>

Code/Framework/AzCore/AzCore/Component/ComponentApplication.cpp

@@ -121,9 +121,9 @@ namespace AZ
         return environment ? environment->Get() : nullptr;
     }
 
-    ComponentApplication::EventLoggerDeleter::EventLoggerDeleter() noexcept= default;
+    ComponentApplication::EventLoggerDeleter::EventLoggerDeleter() noexcept = default;
     ComponentApplication::EventLoggerDeleter::EventLoggerDeleter(bool skipDelete) noexcept
-        : m_skipDelete{skipDelete}
+        : m_skipDelete{ skipDelete }
     {}
     void ComponentApplication::EventLoggerDeleter::operator()(AZ::Debug::LocalFileEventLogger* ptr)
     {
@@ -332,27 +332,27 @@ namespace AZ
                     ->Value("Stack trace always", Debug::AllocationRecords::RECORD_FULL);
                 ec->Class<Descriptor>("System memory settings", "Settings for managing application memory usage")
                     ->ClassElement(Edit::ClassElements::EditorData, "")
-                        ->Attribute(Edit::Attributes::AutoExpand, true)
+                    ->Attribute(Edit::Attributes::AutoExpand, true)
                     ->DataElement(Edit::UIHandlers::CheckBox, &Descriptor::m_grabAllMemory, "Allocate all memory at startup", "Allocate all system memory at startup if enabled, or allocate as needed if disabled")
                     ->DataElement(Edit::UIHandlers::CheckBox, &Descriptor::m_allocationRecords, "Record allocations", "Collect information on each allocation made for debugging purposes (ignored in Release builds)")
                     ->DataElement(Edit::UIHandlers::CheckBox, &Descriptor::m_allocationRecordsSaveNames, "Record allocations with name saving", "Saves names/filenames information on each allocation made, useful for tracking down leaks in dynamic modules (ignored in Release builds)")
                     ->DataElement(Edit::UIHandlers::CheckBox, &Descriptor::m_allocationRecordsAttemptDecodeImmediately, "Record allocations and attempt immediate decode", "Decode callstacks for each allocation when they occur, used for tracking allocations that fail decoding. Very expensive. (ignored in Release builds)")
                     ->DataElement(Edit::UIHandlers::ComboBox, &Descriptor::m_recordingMode, "Stack recording mode", "Stack record mode. (Ignored in final builds)")
                     ->DataElement(Edit::UIHandlers::SpinBox, &Descriptor::m_stackRecordLevels, "Stack entries to record", "Number of stack levels to record for each allocation (ignored in Release builds)")
-                        ->Attribute(Edit::Attributes::Step, 1)
-                        ->Attribute(Edit::Attributes::Max, 1024)
+                    ->Attribute(Edit::Attributes::Step, 1)
+                    ->Attribute(Edit::Attributes::Max, 1024)
                     ->DataElement(Edit::UIHandlers::CheckBox, &Descriptor::m_autoIntegrityCheck, "Validate allocations", "Check allocations for integrity on each allocation/free (ignored in Release builds)")
                     ->DataElement(Edit::UIHandlers::CheckBox, &Descriptor::m_markUnallocatedMemory, "Mark freed memory", "Set memory to 0xcd when a block is freed for debugging (ignored in Release builds)")
                     ->DataElement(Edit::UIHandlers::CheckBox, &Descriptor::m_doNotUsePools, "Don't pool allocations", "Pipe pool allocations in system/tree heap (ignored in Release builds)")
                     ->DataElement(Edit::UIHandlers::SpinBox, &Descriptor::m_pageSize, "Page size", "Memory page size in bytes (must be OS page size aligned)")
-                        ->Attribute(Edit::Attributes::Step, 1024)
+                    ->Attribute(Edit::Attributes::Step, 1024)
                     ->DataElement(Edit::UIHandlers::SpinBox, &Descriptor::m_poolPageSize, "Pool page size", "Memory pool page size in bytes (must be a multiple of page size)")
-                        ->Attribute(Edit::Attributes::Max, &Descriptor::m_pageSize)
-                        ->Attribute(Edit::Attributes::Step, 1024)
+                    ->Attribute(Edit::Attributes::Max, &Descriptor::m_pageSize)
+                    ->Attribute(Edit::Attributes::Step, 1024)
                     ->DataElement(Edit::UIHandlers::SpinBox, &Descriptor::m_memoryBlockAlignment, "Block alignment", "Memory block alignment in bytes (must be multiple of the page size)")
-                        ->Attribute(Edit::Attributes::Step, &Descriptor::m_pageSize)
+                    ->Attribute(Edit::Attributes::Step, &Descriptor::m_pageSize)
                     ->DataElement(Edit::UIHandlers::SpinBox, &Descriptor::m_memoryBlocksByteSize, "Block size", "Memory block size in bytes (must be multiple of the page size)")
-                        ->Attribute(Edit::Attributes::Step, &Descriptor::m_pageSize)
+                    ->Attribute(Edit::Attributes::Step, &Descriptor::m_pageSize)
                     ->DataElement(Edit::UIHandlers::SpinBox, &Descriptor::m_reservedOS, "OS reserved memory", "System memory reserved for OS (used only when 'Allocate all memory at startup' is true)")
                     ->DataElement(Edit::UIHandlers::SpinBox, &Descriptor::m_reservedDebug, "Memory reserved for debugger", "System memory reserved for Debug allocator, like memory tracking (used only when 'Allocate all memory at startup' is true)")
                     ->DataElement(Edit::UIHandlers::CheckBox, &Descriptor::m_enableDrilling, "Enable Driller", "Enable Drilling support for the application (ignored in Release builds)")
@@ -419,11 +419,11 @@ namespace AZ
         }
         else
         {
-             azstrcpy(m_commandLineBuffer, AZ_ARRAY_SIZE(m_commandLineBuffer), "no_argv_supplied");
+            azstrcpy(m_commandLineBuffer, AZ_ARRAY_SIZE(m_commandLineBuffer), "no_argv_supplied");
             // use a "valid" value here.  This is because Qt and potentially other third party libraries require
             // that ArgC be 'at least 1' and that (*argV)[0] be a valid pointer to a real null terminated string.
-             m_argC = 1;
-             m_argV = &m_commandLineBufferAddress;
+            m_argC = 1;
+            m_argV = &m_commandLineBufferAddress;
         }
 
         // Create the Event logger if it doesn't exist, otherwise reuse the one registered
@@ -557,8 +557,8 @@ namespace AZ
 
     void ReportBadEngineRoot()
     {
-        AZStd::string errorMessage = {"Unable to determine a valid path to the engine.\n"
-                                      "Check parameters such as --project-path and --engine-path and make sure they are valid.\n"};
+        AZStd::string errorMessage = { "Unable to determine a valid path to the engine.\n"
+                                      "Check parameters such as --project-path and --engine-path and make sure they are valid.\n" };
         if (auto registry = AZ::SettingsRegistry::Get(); registry != nullptr)
         {
             AZ::SettingsRegistryInterface::FixedValueString filePathErrorStr;
@@ -614,7 +614,6 @@ namespace AZ
         AZ_Assert(m_systemEntity, "SystemEntity failed to initialize!");
 
         AddRequiredSystemComponents(m_systemEntity.get());
-        //m_currentTime = GetElapsedTimeUs();
         m_isStarted = true;
         return m_systemEntity.get();
     }
@@ -1372,38 +1371,44 @@ namespace AZ
 
     void ComponentApplication::Tick(float deltaOverride /*= -1.f*/)
     {
-        AZ_PROFILE_SCOPE(System, "Component application simulation tick");
-        AZStd::chrono::system_clock::time_point now = AZStd::chrono::system_clock::now();
-        m_deltaTime = 0.0f;
-        if (now >= m_currentTime)
         {
-            AZStd::chrono::duration<float> delta = now - m_currentTime;
-            m_deltaTime = deltaOverride >= 0.f ? deltaOverride : delta.count();
-        }
-        {
-            AZ_PROFILE_SCOPE(AzCore, "ComponentApplication::Tick:ExecuteQueuedEvents");
-            TickBus::ExecuteQueuedEvents();
-        }
-        m_currentTime = now;
-        {
-            AZ_PROFILE_SCOPE(AzCore, "ComponentApplication::Tick:OnTick");
-            EBUS_EVENT(TickBus, OnTick, m_deltaTime, ScriptTimePoint(now));
-        }
+            AZ_PROFILE_SCOPE(System, "Component application simulation tick");
 
-        // If tick rate limiting is on, ensure (1 / g_simulation_tick_rate) ms has elapsed since the last frame,
-        // sleeping if there's still time remaining.
-        if (g_simulation_tick_rate > 0.f)
-        {
-            now = AZStd::chrono::system_clock::now();
+            AZStd::chrono::system_clock::time_point now = AZStd::chrono::system_clock::now();
 
-            // Work in microsecond durations here as that's the native measurement time for time_point
-            constexpr float microsecondsPerSecond = 1000.f * 1000.f;
-            const AZStd::chrono::microseconds timeBudgetPerTick(static_cast<int>(microsecondsPerSecond / g_simulation_tick_rate));
-            AZStd::chrono::microseconds timeUntilNextTick = m_currentTime + timeBudgetPerTick - now;
+            m_deltaTime = 0.0f;
 
-            if (timeUntilNextTick.count() > 0)
+            if (now >= m_currentTime)
             {
-                AZStd::this_thread::sleep_for(timeUntilNextTick);
+                AZStd::chrono::duration<float> delta = now - m_currentTime;
+                m_deltaTime = deltaOverride >= 0.f ? deltaOverride : delta.count();
+            }
+
+            {
+                AZ_PROFILE_SCOPE(AzCore, "ComponentApplication::Tick:ExecuteQueuedEvents");
+                TickBus::ExecuteQueuedEvents();
+            }
+            m_currentTime = now;
+            {
+                AZ_PROFILE_SCOPE(AzCore, "ComponentApplication::Tick:OnTick");
+                EBUS_EVENT(TickBus, OnTick, m_deltaTime, ScriptTimePoint(now));
+            }
+
+            // If tick rate limiting is on, ensure (1 / g_simulation_tick_rate) ms has elapsed since the last frame,
+            // sleeping if there's still time remaining.
+            if (g_simulation_tick_rate > 0.f)
+            {
+                now = AZStd::chrono::system_clock::now();
+
+                // Work in microsecond durations here as that's the native measurement time for time_point
+                constexpr float microsecondsPerSecond = 1000.f * 1000.f;
+                const AZStd::chrono::microseconds timeBudgetPerTick(static_cast<int>(microsecondsPerSecond / g_simulation_tick_rate));
+                AZStd::chrono::microseconds timeUntilNextTick = m_currentTime + timeBudgetPerTick - now;
+
+                if (timeUntilNextTick.count() > 0)
+                {
+                    AZStd::this_thread::sleep_for(timeUntilNextTick);
+                }
             }
         }
     }
@@ -1555,5 +1560,4 @@ namespace AZ
             AZ::SettingsRegistryScriptUtils::ReflectSettingsRegistryToBehaviorContext(*behaviorContext);
         }
     }
-
 } // namespace AZ

Code/Framework/AzCore/AzCore/Component/ComponentApplication.h

@@ -5,13 +5,13 @@
  * SPDX-License-Identifier: Apache-2.0 OR MIT
  *
  */
+
 #pragma once
 
 #include <AzCore/Component/ComponentApplicationBus.h>
 #include <AzCore/Component/Component.h>
 #include <AzCore/Component/Entity.h>
 #include <AzCore/Component/TickBus.h>
-#include <AzCore/Time/ITime.h>
 #include <AzCore/Memory/AllocationRecords.h>
 #include <AzCore/Debug/BudgetTracker.h>
 #include <AzCore/Memory/OSAllocator.h>
@@ -377,14 +377,14 @@ namespace AZ
         EntityRemovedEvent                          m_entityRemovedEvent;
         EntityAddedEvent                            m_entityActivatedEvent;
         EntityRemovedEvent                          m_entityDeactivatedEvent;
-        AZ::IConsole*                               m_console{};
+        AZ::IConsole* m_console{};
         Descriptor                                  m_descriptor;
         bool                                        m_isStarted{ false };
         bool                                        m_isSystemAllocatorOwner{ false };
         bool                                        m_isOSAllocatorOwner{ false };
         bool                                        m_ownsConsole{};
-        void*                                       m_fixedMemoryBlock{ nullptr }; //!< Pointer to the memory block allocator, so we can free it OnDestroy.
-        IAllocatorAllocate*                         m_osAllocator{ nullptr };
+        void* m_fixedMemoryBlock{ nullptr }; //!< Pointer to the memory block allocator, so we can free it OnDestroy.
+        IAllocatorAllocate* m_osAllocator{ nullptr };
         EntitySetType                               m_entities;
         AZ::IO::FixedMaxPath                        m_exeDirectory;
         AZ::IO::FixedMaxPath                        m_engineRoot;
@@ -405,11 +405,11 @@ namespace AZ
         // we create a buffer that can be written to (up to AZ_MAX_PATH_LEN) and then
         // pack it with a single param.
         char                                        m_commandLineBuffer[AZ_MAX_PATH_LEN];
-        char*                                       m_commandLineBufferAddress{ m_commandLineBuffer };
+        char* m_commandLineBufferAddress{ m_commandLineBuffer };
 
         StartupParameters                           m_startupParameters;
 
-        char**                                      m_argV{ nullptr };
+        char** m_argV{ nullptr };
         int                                         m_argC{ 0 };
         AZ::CommandLine                             m_commandLine; // < Stores parsed command line supplied to the constructor
 

Gems/Multiplayer/Code/Include/Multiplayer/IMultiplayer.h

@@ -45,6 +45,7 @@ namespace Multiplayer
     using ClientMigrationStartEvent = AZ::Event<ClientInputId>;
     using ClientMigrationEndEvent = AZ::Event<>;
     using ClientDisconnectedEvent = AZ::Event<>;
+    using NotifyClientMigrationEvent = AZ::Event<HostId, uint64_t, ClientInputId>;
     using ConnectionAcquiredEvent = AZ::Event<MultiplayerAgentDatum>;
     using SessionInitEvent = AZ::Event<AzNetworking::INetworkInterface*>;
     using SessionShutdownEvent = AZ::Event<AzNetworking::INetworkInterface*>;
@@ -80,34 +81,38 @@ namespace Multiplayer
         //! @param state The state of this connection
         virtual void InitializeMultiplayer(MultiplayerAgentType state) = 0;
 
-        //! Starts hosting a server
+        //! Starts hosting a server.
         //! @param port The port to listen for connection on
         //! @param isDedicated Whether the server is dedicated or client hosted
         //! @return if the application successfully started hosting
         virtual bool StartHosting(uint16_t port, bool isDedicated = true) = 0;
 
-        //! Connects to the specified IP as a Client
+        //! Connects to the specified IP as a Client.
         //! @param remoteAddress The domain or IP to connect to
         //! @param port The port to connect to
         //! @result if a connection was successfully created
         virtual bool Connect(AZStd::string remoteAddress, uint16_t port) = 0;
 
-        // Disconnects all multiplayer connections, stops listening on the server and invokes handlers appropriate to network context
+        // Disconnects all multiplayer connections, stops listening on the server and invokes handlers appropriate to network context.
         //! @param reason The reason for terminating connections
         virtual void Terminate(AzNetworking::DisconnectReason reason) = 0;
 
-        //! Adds a ClientMigrationStartEvent Handler which is invoked at the start of a client migration
+        //! Adds a ClientMigrationStartEvent Handler which is invoked at the start of a client migration.
         //! @param handler The ClientMigrationStartEvent Handler to add
         virtual void AddClientMigrationStartEventHandler(ClientMigrationStartEvent::Handler& handler) = 0;
 
-        //! Adds a ClientMigrationEndEvent Handler which is invoked when a client completes migration
+        //! Adds a ClientMigrationEndEvent Handler which is invoked when a client completes migration.
         //! @param handler The ClientMigrationEndEvent Handler to add
         virtual void AddClientMigrationEndEventHandler(ClientMigrationEndEvent::Handler& handler) = 0;
 
-        //! Adds a ClientDisconnectedEvent Handler which is invoked on the client when a disconnection occurs
+        //! Adds a ClientDisconnectedEvent Handler which is invoked on the client when a disconnection occurs.
         //! @param handler The ClientDisconnectedEvent Handler to add
         virtual void AddClientDisconnectedHandler(ClientDisconnectedEvent::Handler& handler) = 0;
 
+        //! Adds a NotifyClientMigrationEvent Handler which is invoked when a client migrates from one host to another.
+        //! @param handler The NotifyClientMigrationEvent Handler to add
+        virtual void AddNotifyClientMigrationHandler(NotifyClientMigrationEvent::Handler& handler) = 0;
+
         //! Adds a ConnectionAcquiredEvent Handler which is invoked when a new endpoint connects to the session.
         //! @param handler The ConnectionAcquiredEvent Handler to add
         virtual void AddConnectionAcquiredHandler(ConnectionAcquiredEvent::Handler& handler) = 0;
@@ -120,7 +125,13 @@ namespace Multiplayer
         //! @param handler The SessionShutdownEvent handler to add
         virtual void AddSessionShutdownHandler(SessionShutdownEvent::Handler& handler) = 0;
 
-        //! Sends a packet telling if entity update messages can be sent
+        //! Signals a NotifyClientMigrationEvent with the provided parameters.
+        //! @param hostId            the host id of the host the client is migrating to
+        //! @param userIdentifier    the user identifier the client will provide the new host to validate identity
+        //! @param lastClientInputId the last processed clientInputId by the current host
+        virtual void SendNotifyClientMigrationEvent(HostId hostId, uint64_t userIdentifier, ClientInputId lastClientInputId);
+
+        //! Sends a packet telling if entity update messages can be sent.
         //! @param readyForEntityUpdates Ready for entity updates or not
         virtual void SendReadyForEntityUpdates(bool readyForEntityUpdates) = 0;
 
@@ -132,7 +143,7 @@ namespace Multiplayer
         //! @return the current server time in milliseconds
         virtual AZ::TimeMs GetCurrentHostTimeMs() const = 0;
 
-        //! Returns the current blend factor for client side interpolation
+        //! Returns the current blend factor for client side interpolation.
         //! This value is only relevant on the client and is used to smooth between host frames
         //! @return the current blend factor
         virtual float GetCurrentBlendFactor() const = 0;

Gems/Multiplayer/Code/Source/AutoGen/AutoComponent_Header.jinja

@@ -403,6 +403,8 @@ namespace {{ Component.attrib['Namespace'] }}
         : public Multiplayer::MultiplayerController
     {
     public:
+        using ComponentType = {{ ComponentName }};
+
         {{ ControllerBaseName }}({{ ComponentName }}& owner);
         ~{{ ControllerBaseName }}() override = default;
 

Gems/Multiplayer/Code/Source/AutoGen/Multiplayer.AutoPackets.xml

@@ -40,8 +40,8 @@
     </Packet>
 
     <Packet Name="ClientMigration" Desc="Tell a client to migrate to a new server">
-        <Member Type="uint64_t" Name="temporaryUserIdentifier" Init="0" />
-        <Member Type="AzNetworking::IpAddress" Name="remoteServerAddress" Init="AzNetworking::IpAddress()" />
-        <Member Type="AZ::TimeMs" Name="lastInputGameTimeMs" Init="AZ::TimeMs{ 0 }" />
+		<Member Type="AzNetworking::IpAddress" Name="remoteServerAddress" Init="AzNetworking::IpAddress()" />
+		<Member Type="uint64_t" Name="temporaryUserIdentifier" Init="0" />
+		<Member Type="Multiplayer::ClientInputId" Name="lastClientInputId" Init="Multiplayer::ClientInputId{ 0 }" />
     </Packet>
 </PacketGroup>

Gems/Multiplayer/Code/Source/ConnectionData/ServerToClientConnectionData.cpp

@@ -7,7 +7,10 @@
  */
 
 #include <Source/ConnectionData/ServerToClientConnectionData.h>
+#include <Source/AutoGen/Multiplayer.AutoPackets.h>
+#include <Multiplayer/Components/LocalPredictionPlayerInputComponent.h>
 #include <Multiplayer/IMultiplayer.h>
+#include <AzNetworking/Utilities/EncryptionCommon.h>
 
 namespace Multiplayer
 {
@@ -95,36 +98,31 @@ namespace Multiplayer
         [[maybe_unused]] AzNetworking::ConnectionId connectionId
     )
     {
-        //Multiplayer::ServerAddrInfo serverAddr;
-        //if (gNovaGame->GetMultiplayerworkAgent().GetServerToServerNetwork().GetServerAddrInfoFromConnectionId(newConnectionId, serverAddr) == false)
-        //{
-        //    AZLOG_WARN("MigrateClient::Failed to find servershard address, userID:%d", static_cast<uint32_t>(GetUserId()));
-        //    return;
-        //}
-        //
-        //Multiplayer::GameTimePoint migratedClientGameTimePoint;
-        //
-        //if (m_ControlledEntity != nullptr)
-        //{
-        //    if (const PlayerNetworkInputComponent::Authority* pComponent = Multiplayer::FindController<PlayerNetworkInputComponent::Authority>(m_ControlledEntity))
-        //    {
-        //        migratedClientGameTimePoint = pComponent->GetLastInputId().GetServerGameTimePoint();
-        //    }
-        //}
-        //
-        // generate crypto-rand user identifier, send to both server and client so they can negotiate the autonomous entity to assume predictive control over after migration
-        //const uint64_t randomUserIdentifier = 0;
-        //
-        //// Tell the server a new client is about to join
-        //MultiplayerPackets::NotifyClientMigration notifyClientMigration(randomUserIdentifier);
-        //gNovaGame->GetMultiplayerworkAgent().GetServerToServerNetwork().SendReliablePacket(newConnectionId, notifyClientMigration);
-        //
-        //// Tell the client who to join
-        //MultiplayerPackets::ClientMigration clientMigration(randomUserIdentifier, serverAddr, migratedClientGameTimePoint);
-        //GetConnection()->SendReliablePacket(clientMigration);
-        //
-        //m_controlledEntity = nullptr;
-        //m_canSendUpdates = false;
+        AzNetworking::IpAddress serverAddress;
+        // serverAddress = GetHost(remoteHostId).GetAddress();
+
+        ClientInputId migratedClientInputId = ClientInputId{ 0 };
+        if (m_controlledEntity != nullptr)
+        {
+            auto controller = m_controlledEntity.FindController<LocalPredictionPlayerInputComponentController>();
+            if (controller != nullptr)
+            {
+                migratedClientInputId = controller->GetLastInputId();
+            }
+        }
+
+        // Generate crypto-rand user identifier, send to both server and client so they can negotiate the autonomous entity to assume predictive control over after migration
+        const uint64_t randomUserIdentifier = AzNetworking::CryptoRand64();
+
+        // Tell the new host that a client is about to (re)join
+        GetMultiplayer()->SendNotifyClientMigrationEvent(remoteHostId, randomUserIdentifier, migratedClientInputId);
+
+        // Tell the client who to join
+        MultiplayerPackets::ClientMigration clientMigration(serverAddress, randomUserIdentifier, migratedClientInputId);
+        GetConnection()->SendReliablePacket(clientMigration);
+
+        m_controlledEntity = NetworkEntityHandle();
+        m_canSendUpdates = false;
     }
 
     void ServerToClientConnectionData::OnGameplayStarted()

Gems/Multiplayer/Code/Source/MultiplayerSystemComponent.cpp

@@ -617,7 +617,7 @@ namespace Multiplayer
         auto visitor = [](IConnection& connection) { connection.Disconnect(DisconnectReason::ClientMigrated, TerminationEndpoint::Local); };
         m_networkInterface->GetConnectionSet().VisitConnections(visitor);
         AZLOG_INFO("Migrating to new server shard");
-        //m_clientMigrateStartEvent(packet.GetLastInputGameTimeMs());
+        m_clientMigrationStartEvent.Signal(ClientInputId{ 0 });
         m_networkInterface->Connect(packet.GetRemoteServerAddress());
         return true;
     }
@@ -795,6 +795,11 @@ namespace Multiplayer
         handler.Connect(m_clientDisconnectedEvent);
     }
 
+    void MultiplayerSystemComponent::AddNotifyClientMigrationHandler(NotifyClientMigrationEvent::Handler& handler)
+    {
+        handler.Connect(m_notifyClientMigrationEvent);
+    }
+
     void MultiplayerSystemComponent::AddConnectionAcquiredHandler(ConnectionAcquiredEvent::Handler& handler)
     {
         handler.Connect(m_connectionAcquiredEvent);
@@ -810,6 +815,11 @@ namespace Multiplayer
         handler.Connect(m_shutdownEvent);
     }
 
+    void MultiplayerSystemComponent::SendNotifyClientMigrationEvent(HostId hostId, uint64_t userIdentifier, ClientInputId lastClientInputId)
+    {
+        m_notifyClientMigrationEvent.Signal(hostId, userIdentifier, lastClientInputId);
+    }
+
     void MultiplayerSystemComponent::SendReadyForEntityUpdates(bool readyForEntityUpdates)
     {
         IConnectionSet& connectionSet = m_networkInterface->GetConnectionSet();

Gems/Multiplayer/Code/Source/MultiplayerSystemComponent.h

@@ -111,9 +111,11 @@ namespace Multiplayer
         void AddClientMigrationStartEventHandler(ClientMigrationStartEvent::Handler& handler) override;
         void AddClientMigrationEndEventHandler(ClientMigrationEndEvent::Handler& handler) override;
         void AddClientDisconnectedHandler(ClientDisconnectedEvent::Handler& handler) override;
+        void AddNotifyClientMigrationHandler(NotifyClientMigrationEvent::Handler& handler) override;
         void AddConnectionAcquiredHandler(ConnectionAcquiredEvent::Handler& handler) override;
         void AddSessionInitHandler(SessionInitEvent::Handler& handler) override;
         void AddSessionShutdownHandler(SessionShutdownEvent::Handler& handler) override;
+        void SendNotifyClientMigrationEvent(HostId hostId, uint64_t userIdentifier, ClientInputId lastClientInputId) override;
         void SendReadyForEntityUpdates(bool readyForEntityUpdates) override;
         AZ::TimeMs GetCurrentHostTimeMs() const override;
         float GetCurrentBlendFactor() const override;
@@ -154,6 +156,7 @@ namespace Multiplayer
         ClientDisconnectedEvent m_clientDisconnectedEvent;
         ClientMigrationStartEvent m_clientMigrationStartEvent;
         ClientMigrationEndEvent m_clientMigrationEndEvent;
+        NotifyClientMigrationEvent m_notifyClientMigrationEvent;
 
         AZStd::queue<AZStd::string> m_pendingConnectionTickets;