dynamic_config.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
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  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 MYSQL_HARNESS_DYNAMIC_CONFIG_INCLUDED
#define MYSQL_HARNESS_DYNAMIC_CONFIG_INCLUDED
 
#include <map>
#include <string>
#include <variant>
 
#ifdef RAPIDJSON_NO_SIZETYPEDEFINE
#include "my_rapidjson_size_t.h"
#endif
 
#include <rapidjson/document.h>
 
#include "harness_export.h"
 
namespace mysql_harness {
 
/** @class DynamicConfig
 *
 * @brief Respresents the current Router configuration. It is initialized at
 * start with the defaults and configuration from the configuration file(s).
 */
class HARNESS_EXPORT DynamicConfig {
 public:
  using OptionName = std::string;
  // std::monotstate is used as "option not set"
  using OptionValue =
      std::variant<std::monostate, int64_t, bool, double, std::string>;
 
  // The first string is the plugin name. The second string is the plugin
  // section key if there are multiple plugin instances.
  // Examples:
  // for metadata_cache <"metadata_cache", "">
  // for routing:bootstrap_ro
  //        <"endoints", "bootstrap_ro">
  // for filelog <"loggers", "filelog">
  using SectionId = std::pair<std::string, std::string>;
  using SectionOptions = std::map<OptionName, OptionValue>;
 
  using JsonAllocator = rapidjson::CrtAllocator;
  using JsonDocument =
      rapidjson::GenericDocument<rapidjson::UTF8<>, JsonAllocator>;
 
  /**
   * Sets a given option in a given section to a specific value.
   *
   * @param section_id  identifier of a section for this operation
   * @param option_name name of the option inside a section for this operation
   * @param value       value to be set
   */
  void set_option_configured(const SectionId &section_id,
                             std::string_view option_name,
                             const OptionValue &value);
 
  /**
   * Sets a default for an option in a given section to a specific value.
   *
   * @param section_id  identifier of a section for this operation
   * @param option_name name of the option inside a section for this operation
   * @param default_value_cluster default value for srtandalne cluster setup to
   *                              be set
   * @param default_value_clusterset  default value for the clusterset setup to
   *                                  be set
   */
  void set_option_default(const SectionId &section_id,
                          std::string_view option_name,
                          const OptionValue &default_value_cluster,
                          const OptionValue &default_value_clusterset);
 
  /**
   * Sets a default for an option in a given section to a specific value.
   * Overload for more common case when cluster and clusterset values are the
   * same.
   *
   * @param section_id    identifier of a section for this operation
   * @param option_name   name of the option inside a section for this operation
   * @param default_value default value for both srtandalne cluster and
   *                      clusterset setup to be set
   */
  void set_option_default(const SectionId &section_id,
                          std::string_view option_name,
                          const OptionValue &default_value);
 
  /**
   * @brief Type of the options stored in the dynamic configuration object.
   */
  enum class ValueType {
    ConfiguredValue,      // value currently configured
    DefaultForCluster,    // default value for the standalone cluster setup
    DefaultForClusterSet  // default value for the clusterset setup
  };
 
  /**
   * @brief Return the current configuration options and their values stored in
   * the dynamic configuration object.
   *
   * @param value_type  type of the options to be returned
   *
   * @returns JSON Document containing all the options of a selected type.
   */
  JsonDocument get_json(const ValueType value_type) const;
 
  /**
   * @brief Return the current configuration options and their values stored in
   * the dynamic configuration object as a string.
   *
   * @param value_type  type of the options to be returned
   *
   * @returns JSON string containing all the options of a selected type.
   */
  std::string get_json_as_string(const ValueType value_type) const;
 
  /**
   * Returns a singleton object of DynamicConfig class.
   */
  static DynamicConfig &instance();
 
  /**
   * Clear the DynamicConfig object (remove all registered sections with their
   * option values and defaults).
   */
  void clear();
 
 private:
  DynamicConfig() = default;
  DynamicConfig(const DynamicConfig &) = delete;
  DynamicConfig &operator=(const DynamicConfig &) = delete;
 
  void set_option(const ValueType value_type, const SectionId &section_id,
                  std::string_view option_name, const OptionValue &value);
 
  struct SectionConfig {
    SectionOptions options;
  };
  using Config = std::map<SectionId, SectionConfig>;
 
  Config &get_config(const ValueType value_type);
  Config const &get_config(const ValueType value_type) const;
 
  // stores the currently configured values
  Config configured_;
  // stores the defaults for the standalone cluster configuration
  Config defaults_cluster_;
  // stores the defaults for the clusterset configuration
  Config defaults_clusterset_;
};
 
}  // namespace mysql_harness
 
#endif  // MYSQL_HARNESS_DYNAMIC_CONFIG_INCLUDED