Merge remote-tracking branch 'sophiax851/fix/rotation-missing-node' into ximinez/online-delete-gaps2

* sophiax851/fix/rotation-missing-node:
  fix: Copy archive reads forward during rotation to prevent node loss

include/xrpl/nodestore/DatabaseRotating.h

@@ -41,6 +41,18 @@ public:
         std::unique_ptr<NodeStore::Backend>&& newBackend,
         std::function<void(std::string const& writableName, std::string const& archiveName)> const&
             f) = 0;
+
+    /** Marks an online-delete rotation as in progress (or completed).
+
+        While in flight, a read served by the archive backend is copied
+        forward into the writable backend even for ordinary
+        (duplicate == false) fetches: the archive is about to be deleted,
+        and a node body canonicalized into caches during the rotation
+        window would otherwise survive only in RAM once the archive is
+        dropped.
+    */
+    virtual void
+    setRotationInFlight(bool inFlight) = 0;
 };
 
 }  // namespace xrpl::NodeStore

include/xrpl/nodestore/detail/DatabaseRotatingImp.h

@@ -9,6 +9,7 @@
 #include <xrpl/nodestore/NodeObject.h>
 #include <xrpl/nodestore/Scheduler.h>
 
+#include <atomic>
 #include <cstdint>
 #include <functional>
 #include <memory>
@@ -69,11 +70,22 @@ public:
     void
     sweep() override;
 
+    void
+    setRotationInFlight(bool inFlight) override;
+
 private:
     std::shared_ptr<Backend> writableBackend_;
     std::shared_ptr<Backend> archiveBackend_;
     mutable std::mutex mutex_;
 
+    // True between SHAMapStore starting the cache-freshen phase and the
+    // completion of rotate(). While true, archive hits on ordinary
+    // (duplicate == false) fetches are copied forward into the writable
+    // backend; copyForwardCount_ tallies them per rotation for the
+    // summary line logged at swap.
+    std::atomic<bool> rotationInFlight_{false};
+    std::atomic<std::uint64_t> copyForwardCount_{0};
+
     std::shared_ptr<NodeObject>
     fetchNodeObject(uint256 const& hash, std::uint32_t, FetchReport& fetchReport, bool duplicate)
         override;