entity.h

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  it under the terms of the GNU General Public License, version 2.0,
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*/
 
#ifndef ROUTER_SRC_MYSQL_REST_SERVICE_SRC_MRS_OBSERVABILITY_ENTITY_H_
#define ROUTER_SRC_MYSQL_REST_SERVICE_SRC_MRS_OBSERVABILITY_ENTITY_H_
 
#include <atomic>
#include <cassert>
#include <shared_mutex>
 
namespace mrs {
namespace observability {
 
class Common {
 public:
  static inline std::shared_mutex mutex;
};
 
class Entity : public Common {
 public:
  virtual ~Entity() = default;
 
  virtual uint64_t get_id() const = 0;
  virtual std::string get_name() const = 0;
  virtual uint64_t get_value_and_reset() = 0;
};
 
template <uint64_t counter_id>
class EntityWithId : public Entity {
 public:
  EntityWithId() { assert(!registred_.test_and_set()); }
 
 protected:
#ifndef NDEBUG
  static inline std::atomic_flag registred_;
#endif
};
 
template <uint64_t counter_id>
class EntityCounter : public EntityWithId<counter_id> {
 public:
  static void increment(int32_t inc = 1) {
    auto lock = std::shared_lock<std::shared_mutex>(Common::mutex);
    value_ += inc;
  }
 
  EntityCounter(const std::string &name) : name_{name} {}
 
  uint64_t get_id() const override { return counter_id; }
  std::string get_name() const override { return name_; }
  uint64_t get_value_and_reset() override { return value_.exchange(0); }
 
 protected:
  std::string name_;
  static inline std::atomic<uint64_t> value_;
};
 
template <uint64_t counter_id>
class EntityCounterNotResetable : public EntityCounter<counter_id> {
 public:
  using Parent = EntityCounter<counter_id>;
  using Parent::EntityCounter;
  uint64_t get_value_and_reset() override { return Parent::value_.load(); }
};
 
template <uint64_t counter_id>
class EntityAverageInt : public EntityCounter<counter_id> {
 public:
  using Parent = EntityCounter<counter_id>;
  using Parent::EntityCounter;
 
  static void increment(int32_t inc = 1) {
    auto lock = std::shared_lock<std::shared_mutex>(Common::mutex);
    Parent::value_ += inc;
    ++count_;
  }
 
  uint64_t get_value_and_reset() override {
    return Parent::value_.exchange(0) / count_.exchange(0);
  }
 
 protected:
  static inline std::atomic<uint64_t> count_;
};
 
}  // namespace observability
 
template <uint64_t counter_id>
using Counter = observability::EntityCounter<counter_id>;
 
template <uint64_t counter_id>
using Average = observability::EntityAverageInt<counter_id>;
 
}  // namespace mrs
 
#endif  // ROUTER_SRC_MYSQL_REST_SERVICE_SRC_MRS_OBSERVABILITY_ENTITY_H_