polyglot_garbage_collector.h

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/*
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#ifndef MYSQLSHDK_SCRIPTING_POLYGLOT_LANGUAGES_POLYGLOT_GARBAGE_COLLECTOR_H_
#define MYSQLSHDK_SCRIPTING_POLYGLOT_LANGUAGES_POLYGLOT_GARBAGE_COLLECTOR_H_
#include "utils/polyglot_api_clean.h"
 
#include <chrono>
#include <condition_variable>
#include <memory>
#include <mutex>
#include <optional>
#include <thread>
 
namespace shcore {
namespace polyglot {
 
/**
 * The Garbage Collection logic is determined by the occurrence of events such
 * as:
 *
 * - Statements being executed
 * - Language instances being disposed
 * - Completion of predefined time lapse
 *
 * The trigger for GC operations is defined by the following optional
 * configurations:
 *
 * - Minimal interval (seconds): if defined, the GC will NOT be executed in
 *   periods shorter than this interval.
 * - Minimal executed statements: if defined, the GC will not be executed if
 *   less than the defined number of statements has been executed.
 * - Minimal language instances: if defined, the GC will not be executed if less
 *   than the defined number of language instances have been terminated.
 *
 * Additionally, when the garbage collector may be stopped (i.e. when
 * terminating the application), in such case, a GC operation will be triggered
 * despite the state of the configurable options.
 *
 * This class keeps the Garbage Collection configuration and executes GC in a
 * separate thread based on the configuration and reported events.
 */
class Garbage_collector final {
  enum class State { INITIAL, STARTED, TERMINATED, ERROR };
 
 public:
  using Time_point = std::chrono::time_point<std::chrono::system_clock>;
  Garbage_collector() = default;
  ~Garbage_collector();
 
  Garbage_collector(const Garbage_collector &other) = delete;
  Garbage_collector(Garbage_collector &&other) = delete;
 
  Garbage_collector &operator=(const Garbage_collector &other) = delete;
  Garbage_collector &operator=(Garbage_collector &&other) = delete;
 
  enum class Event { EXECUTED_STATEMENT, TERMINATED_LANGUAGE, TERMINATE };
 
  struct Config {
    std::optional<size_t> interval;
    std::optional<size_t> statements;
    std::optional<size_t> languages;
  };
 
  void notify(Event event);
  void start(Config &&config, poly_isolate isolate);
  void stop();
 
 private:
  void run(poly_isolate isolate);
  void set_state(State state, const std::string &error = "");
  std::mutex m_mutex;
  std::mutex m_state_mutex;
  std::condition_variable m_condition;
  std::unique_ptr<std::thread> m_thread;
 
  State m_state = State::INITIAL;
  std::string m_error;
  Config m_config;
  bool m_terminated = false;
  size_t m_statement_count = 0;
  size_t m_language_count = 0;
 
  Time_point m_last_gctime;
};
 
}  // namespace polyglot
}  // namespace shcore
 
#endif  // MYSQLSHDK_SCRIPTING_POLYGLOT_LANGUAGES_POLYGLOT_GARBAGE_COLLECTOR_H_