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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#pragma once
#include "rocksdb/stats_history.h"
namespace ROCKSDB_NAMESPACE {
// InMemoryStatsHistoryIterator can be used to access stats history that was
// stored by an in-memory two level std::map(DBImpl::stats_history_). It keeps
// a copy of the stats snapshot (in stats_map_) that is currently being pointed
// to, which allows the iterator to access the stats snapshot even when
// the background garbage collecting thread purges it from the source of truth
// (`DBImpl::stats_history_`). In that case, the iterator will continue to be
// valid until a call to `Next()` returns no result and invalidates it. In
// some extreme cases, the iterator may also return fragmented segments of
// stats snapshots due to long gaps between `Next()` calls and interleaved
// garbage collection.
class InMemoryStatsHistoryIterator final : public StatsHistoryIterator {
public:
// Setup InMemoryStatsHistoryIterator to return stats snapshots between
// seconds timestamps [start_time, end_time)
InMemoryStatsHistoryIterator(uint64_t start_time, uint64_t end_time,
DBImpl* db_impl)
: start_time_(start_time),
end_time_(end_time),
valid_(true),
db_impl_(db_impl) {
AdvanceIteratorByTime(start_time_, end_time_);
}
// no copying allowed
InMemoryStatsHistoryIterator(const InMemoryStatsHistoryIterator&) = delete;
void operator=(const InMemoryStatsHistoryIterator&) = delete;
InMemoryStatsHistoryIterator(InMemoryStatsHistoryIterator&&) = delete;
InMemoryStatsHistoryIterator& operator=(InMemoryStatsHistoryIterator&&) =
delete;
~InMemoryStatsHistoryIterator() override;
bool Valid() const override;
Status status() const override;
// Move to the next stats snapshot currently available
// This function may invalidate the iterator
// REQUIRES: Valid()
void Next() override;
// REQUIRES: Valid()
uint64_t GetStatsTime() const override;
// This function is idempotent
// REQUIRES: Valid()
const std::map<std::string, uint64_t>& GetStatsMap() const override;
private:
// advance the iterator to the next stats history record with timestamp
// between [start_time, end_time)
void AdvanceIteratorByTime(uint64_t start_time, uint64_t end_time);
uint64_t time_;
uint64_t start_time_;
uint64_t end_time_;
std::map<std::string, uint64_t> stats_map_;
Status status_;
bool valid_;
DBImpl* db_impl_;
};
} // namespace ROCKSDB_NAMESPACE
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