X-Git-Url: https://gerrit.opnfv.org/gerrit/gitweb?a=blobdiff_plain;f=src%2Fceph%2Fsrc%2Frgw%2Frgw_period_history.cc;fp=src%2Fceph%2Fsrc%2Frgw%2Frgw_period_history.cc;h=895700f6897bc17244558d8f3035e00ca74bb3f9;hb=812ff6ca9fcd3e629e49d4328905f33eee8ca3f5;hp=0000000000000000000000000000000000000000;hpb=15280273faafb77777eab341909a3f495cf248d9;p=stor4nfv.git

diff --git a/src/ceph/src/rgw/rgw_period_history.cc b/src/ceph/src/rgw/rgw_period_history.cc
new file mode 100644
index 0000000..895700f
--- /dev/null
+++ b/src/ceph/src/rgw/rgw_period_history.cc
@@ -0,0 +1,351 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#include "rgw_period_history.h"
+#include "rgw_rados.h"
+
+#include "include/assert.h"
+
+#define dout_subsys ceph_subsys_rgw
+
+#undef dout_prefix
+#define dout_prefix (*_dout << "rgw period history: ")
+
+/// an ordered history of consecutive periods
+class RGWPeriodHistory::History : public bi::avl_set_base_hook<> {
+ public:
+  std::deque<RGWPeriod> periods;
+
+  epoch_t get_oldest_epoch() const {
+    return periods.front().get_realm_epoch();
+  }
+  epoch_t get_newest_epoch() const {
+    return periods.back().get_realm_epoch();
+  }
+  bool contains(epoch_t epoch) const {
+    return get_oldest_epoch() <= epoch && epoch <= get_newest_epoch();
+  }
+  RGWPeriod& get(epoch_t epoch) {
+    return periods[epoch - get_oldest_epoch()];
+  }
+  const RGWPeriod& get(epoch_t epoch) const {
+    return periods[epoch - get_oldest_epoch()];
+  }
+  const std::string& get_predecessor_id() const {
+    return periods.front().get_predecessor();
+  }
+};
+
+/// value comparison for avl_set
+bool operator<(const RGWPeriodHistory::History& lhs,
+               const RGWPeriodHistory::History& rhs)
+{
+  return lhs.get_newest_epoch() < rhs.get_newest_epoch();
+}
+
+/// key-value comparison for avl_set
+struct NewestEpochLess {
+  bool operator()(const RGWPeriodHistory::History& value, epoch_t key) const {
+    return value.get_newest_epoch() < key;
+  }
+};
+
+
+using Cursor = RGWPeriodHistory::Cursor;
+
+const RGWPeriod& Cursor::get_period() const
+{
+  std::lock_guard<std::mutex> lock(*mutex);
+  return history->get(epoch);
+}
+bool Cursor::has_prev() const
+{
+  std::lock_guard<std::mutex> lock(*mutex);
+  return epoch > history->get_oldest_epoch();
+}
+bool Cursor::has_next() const
+{
+  std::lock_guard<std::mutex> lock(*mutex);
+  return epoch < history->get_newest_epoch();
+}
+
+bool operator==(const Cursor& lhs, const Cursor& rhs)
+{
+  return lhs.history == rhs.history && lhs.epoch == rhs.epoch;
+}
+
+bool operator!=(const Cursor& lhs, const Cursor& rhs)
+{
+  return !(lhs == rhs);
+}
+
+class RGWPeriodHistory::Impl final {
+ public:
+  Impl(CephContext* cct, Puller* puller, const RGWPeriod& current_period);
+  ~Impl();
+
+  Cursor get_current() const { return current_cursor; }
+  Cursor attach(RGWPeriod&& period);
+  Cursor insert(RGWPeriod&& period);
+  Cursor lookup(epoch_t realm_epoch);
+
+ private:
+  /// an intrusive set of histories, ordered by their newest epoch. although
+  /// the newest epoch of each history is mutable, the ordering cannot change
+  /// because we prevent the histories from overlapping
+  using Set = bi::avl_set<RGWPeriodHistory::History>;
+
+  /// insert the given period into the period history, creating new unconnected
+  /// histories or merging existing histories as necessary. expects the caller
+  /// to hold a lock on mutex. returns a valid cursor regardless of whether it
+  /// ends up in current_history, though cursors in other histories are only
+  /// valid within the context of the lock
+  Cursor insert_locked(RGWPeriod&& period);
+
+  /// merge the periods from the src history onto the end of the dst history,
+  /// and return an iterator to the merged history
+  Set::iterator merge(Set::iterator dst, Set::iterator src);
+
+  /// construct a Cursor object using Cursor's private constuctor
+  Cursor make_cursor(Set::const_iterator history, epoch_t epoch);
+
+  CephContext *const cct;
+  Puller *const puller; //< interface for pulling missing periods
+  Cursor current_cursor; //< Cursor to realm's current period
+
+  mutable std::mutex mutex; //< protects the histories
+
+  /// set of disjoint histories that are missing intermediate periods needed to
+  /// connect them together
+  Set histories;
+
+  /// iterator to the history that contains the realm's current period
+  Set::const_iterator current_history;
+};
+
+RGWPeriodHistory::Impl::Impl(CephContext* cct, Puller* puller,
+                             const RGWPeriod& current_period)
+  : cct(cct), puller(puller)
+{
+  if (!current_period.get_id().empty()) {
+    // copy the current period into a new history
+    auto history = new History;
+    history->periods.push_back(current_period);
+
+    // insert as our current history
+    current_history = histories.insert(*history).first;
+
+    // get a cursor to the current period
+    current_cursor = make_cursor(current_history, current_period.get_realm_epoch());
+  }
+}
+
+RGWPeriodHistory::Impl::~Impl()
+{
+  // clear the histories and delete each entry
+  histories.clear_and_dispose(std::default_delete<History>{});
+}
+
+Cursor RGWPeriodHistory::Impl::attach(RGWPeriod&& period)
+{
+  if (current_history == histories.end()) {
+    return Cursor{-EINVAL};
+  }
+
+  const auto epoch = period.get_realm_epoch();
+
+  std::string predecessor_id;
+  for (;;) {
+    {
+      // hold the lock over insert, and while accessing the unsafe cursor
+      std::lock_guard<std::mutex> lock(mutex);
+
+      auto cursor = insert_locked(std::move(period));
+      if (!cursor) {
+        return cursor;
+      }
+      if (current_history->contains(epoch)) {
+        break; // the history is complete
+      }
+
+      // take the predecessor id of the most recent history
+      if (cursor.get_epoch() > current_cursor.get_epoch()) {
+        predecessor_id = cursor.history->get_predecessor_id();
+      } else {
+        predecessor_id = current_history->get_predecessor_id();
+      }
+    }
+
+    if (predecessor_id.empty()) {
+      lderr(cct) << "reached a period with an empty predecessor id" << dendl;
+      return Cursor{-EINVAL};
+    }
+
+    // pull the period outside of the lock
+    int r = puller->pull(predecessor_id, period);
+    if (r < 0) {
+      return Cursor{r};
+    }
+  }
+
+  // return a cursor to the requested period
+  return make_cursor(current_history, epoch);
+}
+
+Cursor RGWPeriodHistory::Impl::insert(RGWPeriod&& period)
+{
+  if (current_history == histories.end()) {
+    return Cursor{-EINVAL};
+  }
+
+  std::lock_guard<std::mutex> lock(mutex);
+
+  auto cursor = insert_locked(std::move(period));
+
+  if (cursor.get_error()) {
+    return cursor;
+  }
+  // we can only provide cursors that are safe to use outside of the mutex if
+  // they're within the current_history, because other histories can disappear
+  // in a merge. see merge() for the special handling of current_history
+  if (cursor.history == &*current_history) {
+    return cursor;
+  }
+  return Cursor{};
+}
+
+Cursor RGWPeriodHistory::Impl::lookup(epoch_t realm_epoch)
+{
+  if (current_history != histories.end() &&
+      current_history->contains(realm_epoch)) {
+    return make_cursor(current_history, realm_epoch);
+  }
+  return Cursor{};
+}
+
+Cursor RGWPeriodHistory::Impl::insert_locked(RGWPeriod&& period)
+{
+  auto epoch = period.get_realm_epoch();
+
+  // find the first history whose newest epoch comes at or after this period
+  auto i = histories.lower_bound(epoch, NewestEpochLess{});
+
+  if (i == histories.end()) {
+    // epoch is past the end of our newest history
+    auto last = --Set::iterator{i}; // last = i - 1
+
+    if (epoch == last->get_newest_epoch() + 1) {
+      // insert at the back of the last history
+      last->periods.emplace_back(std::move(period));
+      return make_cursor(last, epoch);
+    }
+
+    // create a new history for this period
+    auto history = new History;
+    history->periods.emplace_back(std::move(period));
+    histories.insert(last, *history);
+
+    i = Set::s_iterator_to(*history);
+    return make_cursor(i, epoch);
+  }
+
+  if (i->contains(epoch)) {
+    // already resident in this history
+    auto& existing = i->get(epoch);
+    // verify that the period ids match; otherwise we've forked the history
+    if (period.get_id() != existing.get_id()) {
+      lderr(cct) << "Got two different periods, " << period.get_id()
+          << " and " << existing.get_id() << ", with the same realm epoch "
+          << epoch << "! This indicates a fork in the period history." << dendl;
+      return Cursor{-EEXIST};
+    }
+    // update the existing period if we got a newer period epoch
+    if (period.get_epoch() > existing.get_epoch()) {
+      existing = std::move(period);
+    }
+    return make_cursor(i, epoch);
+  }
+
+  if (epoch + 1 == i->get_oldest_epoch()) {
+    // insert at the front of this history
+    i->periods.emplace_front(std::move(period));
+
+    // try to merge with the previous history
+    if (i != histories.begin()) {
+      auto prev = --Set::iterator{i};
+      if (epoch == prev->get_newest_epoch() + 1) {
+        i = merge(prev, i);
+      }
+    }
+    return make_cursor(i, epoch);
+  }
+
+  if (i != histories.begin()) {
+    auto prev = --Set::iterator{i};
+    if (epoch == prev->get_newest_epoch() + 1) {
+      // insert at the back of the previous history
+      prev->periods.emplace_back(std::move(period));
+      return make_cursor(prev, epoch);
+    }
+  }
+
+  // create a new history for this period
+  auto history = new History;
+  history->periods.emplace_back(std::move(period));
+  histories.insert(i, *history);
+
+  i = Set::s_iterator_to(*history);
+  return make_cursor(i, epoch);
+}
+
+RGWPeriodHistory::Impl::Set::iterator
+RGWPeriodHistory::Impl::merge(Set::iterator dst, Set::iterator src)
+{
+  assert(dst->get_newest_epoch() + 1 == src->get_oldest_epoch());
+
+  // always merge into current_history
+  if (src == current_history) {
+    // move the periods from dst onto the front of src
+    src->periods.insert(src->periods.begin(),
+                        std::make_move_iterator(dst->periods.begin()),
+                        std::make_move_iterator(dst->periods.end()));
+    histories.erase_and_dispose(dst, std::default_delete<History>{});
+    return src;
+  }
+
+  // move the periods from src onto the end of dst
+  dst->periods.insert(dst->periods.end(),
+                      std::make_move_iterator(src->periods.begin()),
+                      std::make_move_iterator(src->periods.end()));
+  histories.erase_and_dispose(src, std::default_delete<History>{});
+  return dst;
+}
+
+Cursor RGWPeriodHistory::Impl::make_cursor(Set::const_iterator history,
+                                           epoch_t epoch) {
+  return Cursor{&*history, &mutex, epoch};
+}
+
+
+RGWPeriodHistory::RGWPeriodHistory(CephContext* cct, Puller* puller,
+                                   const RGWPeriod& current_period)
+  : impl(new Impl(cct, puller, current_period)) {}
+
+RGWPeriodHistory::~RGWPeriodHistory() = default;
+
+Cursor RGWPeriodHistory::get_current() const
+{
+  return impl->get_current();
+}
+Cursor RGWPeriodHistory::attach(RGWPeriod&& period)
+{
+  return impl->attach(std::move(period));
+}
+Cursor RGWPeriodHistory::insert(RGWPeriod&& period)
+{
+  return impl->insert(std::move(period));
+}
+Cursor RGWPeriodHistory::lookup(epoch_t realm_epoch)
+{
+  return impl->lookup(realm_epoch);
+}