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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab ft=cpp
#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/ceph_assert.h"
#include "include/types.h"
#include "common/async/yield_context.h"
#include "common/dout.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 DoutPrefixProvider *dpp, const std::string& period_id, RGWPeriod& period,
optional_yield y) = 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(const DoutPrefixProvider *dpp, RGWPeriod&& period, optional_yield y);
/// 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
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