response_cache.h

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/*
  Copyright (c) 2024, 2025, Oracle and/or its affiliates.
 
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License, version 2.0,
  as published by the Free Software Foundation.
 
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  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
 
  You should have received a copy of the GNU General Public License
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  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/
 
#ifndef ROUTER_SRC_MYSQL_REST_SERVICE_SRC_MRS_REST_RESPONSE_CACHE_H_
#define ROUTER_SRC_MYSQL_REST_SERVICE_SRC_MRS_REST_RESPONSE_CACHE_H_
 
#include <atomic>
#include <chrono>
#include <memory>
#include <mutex>
#include <optional>
#include <shared_mutex>
#include <string>
#include <unordered_map>
#include "helper/media_type.h"
#include "http/base/uri.h"
#include "mrs/database/entry/universal_id.h"
 
namespace mrs {
 
class EndpointResponseCache;
 
struct CacheEntry {
  using TimeType = std::chrono::time_point<std::chrono::system_clock>;
 
  std::string data;
  int64_t items = 0;
  std::optional<helper::MediaType> media_type;
  std::optional<std::string> media_type_str;
 
  std::string key;
  TimeType expiration_time;
 
  EndpointResponseCache *owner;
 
  std::shared_ptr<CacheEntry> next_ptr;
  std::shared_ptr<CacheEntry> prev_ptr;
};
 
constexpr const size_t k_default_object_cache_size = 1000000;
 
class ResponseCache {
 public:
  friend class EndpointResponseCache;
  friend class ItemEndpointResponseCache;
  friend class FileEndpointResponseCache;
 
  explicit ResponseCache(const std::string &config_key)
      : config_key_(config_key) {}
 
  void configure(const std::string &options);
 
  size_t max_cache_size() const { return max_size_; }
 
 private:
  void push(std::shared_ptr<CacheEntry> entry);
  void remove(std::shared_ptr<CacheEntry> entry);
  void remove_nolock(std::shared_ptr<CacheEntry> entry);
 
  int remove_all(EndpointResponseCache *cache);
 
  void shrink_object_cache(size_t extra_size = 0);
 
  std::string config_key_;
 
  std::shared_ptr<CacheEntry> newest_entry_;
  std::shared_ptr<CacheEntry> oldest_entry_;
  std::mutex entries_mutex_;
  std::atomic<size_t> cache_size_ = 0;
 
  std::atomic<size_t> max_size_ = k_default_object_cache_size;
};
 
class EndpointResponseCache {
 public:
  using Uri = ::http::base::Uri;
  using UniversalId = ::mrs::database::entry::UniversalId;
 
 protected:
  EndpointResponseCache(ResponseCache *owner, uint64_t ttl_ms);
  virtual ~EndpointResponseCache() = default;
 
  std::shared_ptr<CacheEntry> create_entry(
      const std::string &key, const std::string &data, int64_t items = 0,
      std::optional<helper::MediaType> media_type = {},
      std::optional<std::string> media_type_str = {});
 
  void remove_entry(std::shared_ptr<CacheEntry> entry, bool ejected);
  virtual void remove_entry_nolock(std::shared_ptr<CacheEntry> entry,
                                   bool ejected);
 
  std::shared_ptr<CacheEntry> lookup(const std::string &key);
 
  friend class ResponseCache;
 
  ResponseCache *owner_;
 
  std::chrono::milliseconds ttl_;
 
  std::unordered_map<std::string, std::shared_ptr<CacheEntry>> cache_;
  std::shared_mutex cache_mutex_;
};
 
class ItemEndpointResponseCache : public EndpointResponseCache {
 public:
  ItemEndpointResponseCache(ResponseCache *owner, uint64_t ttl_ms);
  ~ItemEndpointResponseCache() override;
 
  std::shared_ptr<CacheEntry> create_table_entry(const Uri &uri,
                                                 const std::string &user_id,
                                                 const std::string &data,
                                                 int64_t items);
 
  std::shared_ptr<CacheEntry> create_routine_entry(
      const Uri &uri, std::string_view req_body, const std::string &data,
      std::optional<helper::MediaType> media_type = {});
 
  std::shared_ptr<CacheEntry> create_routine_entry(
      const Uri &uri, std::string_view req_body, const std::string &data,
      const std::string &media_type_str);
 
  std::shared_ptr<CacheEntry> lookup_table(const Uri &uri,
                                           const std::string &user_id);
 
  std::shared_ptr<CacheEntry> lookup_routine(const Uri &uri,
                                             std::string_view req_body);
 
 private:
  void remove_entry_nolock(std::shared_ptr<CacheEntry> entry,
                           bool ejected) override;
};
 
class FileEndpointResponseCache : public EndpointResponseCache {
 public:
  explicit FileEndpointResponseCache(ResponseCache *owner);
  ~FileEndpointResponseCache() override;
 
  std::shared_ptr<CacheEntry> create_file_entry(const UniversalId &id,
                                                const std::string &data,
                                                helper::MediaType media_type);
 
  std::shared_ptr<CacheEntry> lookup_file(const UniversalId &id);
 
 private:
  void remove_entry_nolock(std::shared_ptr<CacheEntry> entry,
                           bool ejected) override;
};
 
}  // namespace mrs
 
#endif  // ROUTER_SRC_MYSQL_REST_SERVICE_SRC_MRS_REST_RESPONSE_CACHE_H_