[idd] transport: coordinate recovery requests

idd/LGIdd/transport/CRecoveryHub.h

@@ -0,0 +1,140 @@
+/**
+ * Looking Glass
+ * Copyright © 2017-2026 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#pragma once
+
+#include "CSRWLock.h"
+#include "transport/ITransport.h"
+
+class CRecoveryHub
+{
+public:
+  struct Delivery
+  {
+    SourceKey     source;
+    uint64_t      session = 0;
+    uint32_t      serial  = 0;
+    bool          active  = false;
+    RecoveryState state   = RecoveryState::FAILED;
+    uint32_t      error   = 0;
+  };
+
+private:
+  static constexpr unsigned MAX_EPOCHS   = TRANSPORT_MAX_INSTANCES;
+  // Reserve two independent request correlations per configured instance.
+  static constexpr unsigned MAX_REQUESTS = TRANSPORT_MAX_INSTANCES * 2;
+  static constexpr uint64_t HELPER_TIMEOUT_MS = 20000;
+
+  enum class SlotState
+  {
+    FREE,
+    WAITING,
+    READY,
+  };
+
+  enum class OperationPhase
+  {
+    NONE,
+    IN_FLIGHT,
+    LATCHED,
+  };
+
+  struct Epoch
+  {
+    BackendId backend = 0;
+    uint32_t  epoch   = 0;
+    bool      synced  = false;
+  };
+
+  struct Request
+  {
+    SourceKey source;
+    uint64_t  session  = 0;
+    uint64_t  operation = 0;
+    uint64_t  sequence = 0;
+    uint32_t  serial   = 0;
+    uint32_t  error    = 0;
+    bool      active   = false;
+    SlotState state    = SlotState::FREE;
+    RecoveryState result = RecoveryState::FAILED;
+  };
+
+  struct Operation
+  {
+    OperationPhase phase = OperationPhase::NONE;
+    RecoveryAction action;
+    uint64_t        id = 0;
+  };
+
+  mutable CSRWLock m_lock;
+  Epoch            m_epochs[MAX_EPOCHS];
+  Request          m_requests[MAX_REQUESTS];
+  Operation        m_operation;
+  RecoveryState    m_known = RecoveryState::FAILED;
+  uint64_t         m_session         = 0;
+  uint64_t         m_nextOperation = 1;
+  uint64_t         m_nextRoute     = 1;
+  uint64_t         m_nextSequence  = 1;
+  uint32_t         m_nextSerial    = 2;
+  bool             m_knownValid    = false;
+  bool             m_monitorReady  = false;
+
+  static bool SameSource(const SourceKey& left, const SourceKey& right);
+  static bool SameEpoch(
+    const SourceKey& source, BackendId backend, uint32_t epoch);
+  static bool SameRequest(const Request& request, const SourceKey& source,
+    uint64_t session, uint32_t serial, bool active);
+  static bool SuccessMatches(RecoveryState state, bool active);
+
+  bool EpochAttachedLocked(const SourceKey& source) const;
+  unsigned FindSourceLocked(const SourceKey& source) const;
+  unsigned FindFreeLocked() const;
+  bool ActionMatchesLocked(const RecoveryAction& action) const;
+  uint64_t NextNonzero(uint64_t& value);
+  uint32_t NextSerial();
+  void ClearRequestLocked(Request& request);
+  void SetWaitingLocked(Request& request, const SourceKey& source,
+    uint64_t session, uint32_t serial, bool active, uint64_t operation);
+  void SetReadyLocked(
+    Request& request, RecoveryState state, uint32_t error);
+  void FinishWaitersLocked(RecoveryState state, uint32_t error);
+
+public:
+  CRecoveryHub();
+
+  bool Attach(BackendId backend, uint32_t epoch, bool& syncNow);
+  void Remove(BackendId backend, uint32_t epoch);
+
+  RecoveryAdmission Submit(const SourceKey& source, uint64_t session,
+    uint32_t serial, bool active, uint64_t now,
+    RecoveryAction& action, bool& dispatch);
+  bool DispatchFailed(const RecoveryAction& action, uint32_t error);
+  bool Complete(const RecoveryAction& action,
+    RecoveryState state, uint32_t error);
+  bool Tick(uint64_t now);
+
+  bool TakeDelivery(
+    BackendId backend, uint32_t epoch, Delivery& delivery);
+  bool HasDelivery(BackendId backend, uint32_t epoch) const;
+
+  bool MarkMonitorReady();
+  bool ClaimSync(BackendId backend, uint32_t epoch);
+  bool MonitorReady() const;
+};