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diff --git a/src/ceph/src/rgw/rgw_period_history.h b/src/ceph/src/rgw/rgw_period_history.h
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+++ b/src/ceph/src/rgw/rgw_period_history.h
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+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#ifndef RGW_PERIOD_HISTORY_H
+#define RGW_PERIOD_HISTORY_H
+
+#include <deque>
+#include <mutex>
+#include <system_error>
+#include <boost/intrusive/avl_set.hpp>
+#include "include/assert.h"
+#include "include/types.h"
+
+namespace bi = boost::intrusive;
+
+class RGWPeriod;
+
+/**
+ * RGWPeriodHistory tracks the relative history of all inserted periods,
+ * coordinates the pulling of missing intermediate periods, and provides a
+ * Cursor object for traversing through the connected history.
+ */
+class RGWPeriodHistory final {
+ private:
+  /// an ordered history of consecutive periods
+  class History;
+
+  // comparisons for avl_set ordering
+  friend bool operator<(const History& lhs, const History& rhs);
+  friend struct NewestEpochLess;
+
+  class Impl;
+  std::unique_ptr<Impl> impl;
+
+ public:
+  /**
+   * Puller is a synchronous interface for pulling periods from the master
+   * zone. The abstraction exists mainly to support unit testing.
+   */
+  class Puller {
+   public:
+    virtual ~Puller() = default;
+
+    virtual int pull(const std::string& period_id, RGWPeriod& period) = 0;
+  };
+
+  RGWPeriodHistory(CephContext* cct, Puller* puller,
+                   const RGWPeriod& current_period);
+  ~RGWPeriodHistory();
+
+  /**
+   * Cursor tracks a position in the period history and allows forward and
+   * backward traversal. Only periods that are fully connected to the
+   * current_period are reachable via a Cursor, because other histories are
+   * temporary and can be merged away. Cursors to periods in disjoint
+   * histories, as provided by insert() or lookup(), are therefore invalid and
+   * their operator bool() will return false.
+   */
+  class Cursor final {
+   public:
+    Cursor() = default;
+    explicit Cursor(int error) : error(error) {}
+
+    int get_error() const { return error; }
+
+    /// return false for a default-constructed or error Cursor
+    operator bool() const { return history != nullptr; }
+
+    epoch_t get_epoch() const { return epoch; }
+    const RGWPeriod& get_period() const;
+
+    bool has_prev() const;
+    bool has_next() const;
+
+    void prev() { epoch--; }
+    void next() { epoch++; }
+
+    friend bool operator==(const Cursor& lhs, const Cursor& rhs);
+    friend bool operator!=(const Cursor& lhs, const Cursor& rhs);
+
+   private:
+    // private constructors for RGWPeriodHistory
+    friend class RGWPeriodHistory::Impl;
+
+    Cursor(const History* history, std::mutex* mutex, epoch_t epoch)
+      : history(history), mutex(mutex), epoch(epoch) {}
+
+    int error{0};
+    const History* history{nullptr};
+    std::mutex* mutex{nullptr};
+    epoch_t epoch{0}; //< realm epoch of cursor position
+  };
+
+  /// return a cursor to the current period
+  Cursor get_current() const;
+
+  /// build up a connected period history that covers the span between
+  /// current_period and the given period, reading predecessor periods or
+  /// fetching them from the master as necessary. returns a cursor at the
+  /// given period that can be used to traverse the current_history
+  Cursor attach(RGWPeriod&& period);
+
+  /// insert the given period into an existing history, or create a new
+  /// unconnected history. similar to attach(), but it doesn't try to fetch
+  /// missing periods. returns a cursor to the inserted period iff it's in
+  /// the current_history
+  Cursor insert(RGWPeriod&& period);
+
+  /// search for a period by realm epoch, returning a valid Cursor iff it's in
+  /// the current_history
+  Cursor lookup(epoch_t realm_epoch);
+};
+
+#endif // RGW_PERIOD_HISTORY_H