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/*
* Copyright (C) 2015 Canonical Ltd.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Authored by: Michi Henning <michi.henning@canonical.com>
*/
#pragma once
#include <core/internal/cache_event_indexes.h>
#include <core/persistent_string_cache.h>
#include <leveldb/db.h>
#include <array>
#include <mutex>
#include <sstream>
namespace core
{
namespace internal
{
class PersistentStringCacheStats;
class PersistentStringCacheImpl
{
public:
PersistentStringCacheImpl(std::string const& cache_path,
int64_t max_size_in_bytes,
core::CacheDiscardPolicy policy,
PersistentStringCache* pimpl = nullptr);
PersistentStringCacheImpl(std::string const& cache_path, PersistentStringCache* pimpl = nullptr);
PersistentStringCacheImpl(PersistentStringCacheImpl const&) = delete;
PersistentStringCacheImpl& operator=(PersistentStringCacheImpl const&) = delete;
PersistentStringCacheImpl(PersistentStringCacheImpl&&) = delete;
PersistentStringCacheImpl& operator=(PersistentStringCacheImpl&&) = delete;
~PersistentStringCacheImpl();
bool get(std::string const& key, std::string& value) const;
bool get(std::string const& key, std::string& value, std::string* metadata) const;
bool get_metadata(std::string const& key, std::string& metadata) const;
bool contains_key(std::string const& key) const;
int64_t size() const noexcept;
int64_t size_in_bytes() const noexcept;
int64_t max_size_in_bytes() const noexcept;
int64_t disk_size_in_bytes() const;
CacheDiscardPolicy discard_policy() const noexcept;
core::PersistentCacheStats stats() const;
bool put(std::string const& key,
std::string const& value,
std::chrono::time_point<std::chrono::system_clock> expiry_time = std::chrono::system_clock::time_point());
bool put(std::string const& key,
char const* value,
int64_t size,
std::chrono::time_point<std::chrono::system_clock> expiry_time = std::chrono::system_clock::time_point());
bool put(std::string const& key,
std::string const& value,
std::string const* metadata,
std::chrono::time_point<std::chrono::system_clock> expiry_time = std::chrono::system_clock::time_point());
bool put(std::string const& key,
char const* value_data,
int64_t value_size,
char const* metadata_data,
int64_t metadata_size,
std::chrono::time_point<std::chrono::system_clock> expiry_time = std::chrono::system_clock::time_point());
bool get_or_put(std::string const& key, std::string& value, PersistentStringCache::Loader load_func);
bool get_or_put(std::string const& key,
std::string& value,
std::string* metadata,
PersistentStringCache::Loader load_func);
bool put_metadata(std::string const& key, std::string const& metadata);
bool put_metadata(std::string const& key, char const* metadata, int64_t metadata_size);
bool take(std::string const& key, std::string& value);
bool take(std::string const& key, std::string& value, std::string* metadata);
bool invalidate(std::string const& key);
void invalidate(std::vector<std::string> const& keys);
template<typename It>
void invalidate(It begin, It end);
void invalidate(std::initializer_list<std::string> const& keys);
void invalidate();
bool touch(
std::string const& key,
std::chrono::time_point<std::chrono::system_clock> expiry_time = std::chrono::system_clock::time_point());
void clear_stats() noexcept;
void resize(int64_t size_in_bytes);
void trim_to(int64_t used_size_in_bytes);
void compact();
void set_handler(CacheEvent events, PersistentStringCache::EventCallback cb);
private:
// Simple struct to serialize/deserialize a data tuple.
// For the stringified representation, fields are separated
// by a space.
struct DataTuple
{
int64_t atime; // Last access time, msec since the epoch
int64_t etime; // Expiry time, msec since the epoch
int64_t size; // Size in bytes
DataTuple(int64_t at, int64_t et, int64_t s) noexcept
: atime(at)
, etime(et)
, size(s)
{
}
DataTuple() noexcept
: DataTuple(0, 0, 0)
{
}
DataTuple(std::string const& s) noexcept
{
std::istringstream is(s);
is >> atime >> etime >> size;
assert(!is.bad());
}
DataTuple(DataTuple const&) = default;
DataTuple(DataTuple&&) = default;
DataTuple& operator=(DataTuple const&) = default;
DataTuple& operator=(DataTuple&&) = default;
std::string to_string() const
{
std::ostringstream os;
os << atime << " " << etime << " " << size;
return os.str();
}
};
void init_stats();
void init_db(leveldb::Options options);
bool cache_is_new() const;
void write_version();
void check_version();
void read_settings();
void write_settings();
void read_stats();
void write_stats();
bool read_dirty_flag() const;
void write_dirty_flag(bool is_dirty);
DataTuple get_data(std::string const& key, bool& found) const;
bool get_value_and_metadata(std::string const& key,
DataTuple& data,
std::string& value,
std::string* metadata) const;
void batch_delete(std::string const& key, DataTuple const& data, leveldb::WriteBatch& batch);
void delete_entry(std::string const& key, DataTuple const& data);
void delete_at_least(int64_t bytes_needed, std::string const& skip_key = "");
void call_handler(std::string const& key, core::internal::CacheEventIndex event) const;
std::string make_message(leveldb::Status const& s, std::string const& msg) const;
std::string make_message(std::string const& msg) const;
void throw_if_error(leveldb::Status const& s, std::string const& msg) const;
void throw_logic_error(std::string const& msg) const;
void throw_invalid_argument(std::string const& msg) const;
void throw_corrupt_error(std::string const& msg) const;
PersistentStringCache* pimpl_; // Back-pointer to owning pimpl.
std::unique_ptr<leveldb::Cache> block_cache_; // Must be defined *before* db_!
std::unique_ptr<leveldb::DB> db_;
std::shared_ptr<PersistentStringCacheStats> stats_;
std::array<PersistentStringCache::EventCallback, static_cast<unsigned>(CacheEventIndex::END_)>
handlers_;
mutable std::recursive_mutex mutex_;
};
} // namespace internal
} // namespace core
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