busy.hpp

#pragma once
 
#include <memory>
 
#include <userver/utils/statistics/recentperiod.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace utils::statistics {
 
using Duration = std::chrono::steady_clock::duration;
 
/* Storage of how much time we've spent in work recently, in %.
 * 'max_workers' limits number of threads working at the same time. */
class BusyStorage final {
 public:
  BusyStorage(Duration epoch_duration, Duration history_period,
              size_t max_workers = 1);
 
  ~BusyStorage();
 
  double GetCurrentLoad() const;
 
  using WorkerId = size_t;
 
  WorkerId StartWork();
 
  void StopWork(WorkerId worker_id);
 
 private:
  WorkerId PopWorkerId();
 
  Duration GetNotCommittedLoad(WorkerId worker_id) const;
 
  bool IsAlreadyStarted() const;
 
  bool UpdateCurrentWorkerLoad(std::vector<Duration>& load) const;
 
  struct Impl;
  std::unique_ptr<Impl> pimpl;
 
  friend class BusyMarker;
};
 
/* A RAII-style guard to account code block execution time in BusyStorage.
 * It is reentrant, IOW you may create BusyMarker inside of another BusyMarker
 * and work time is accounted correctly (based on the outer BusyMarker
 * lifetime).
 */
class BusyMarker final {
 public:
  BusyMarker(BusyStorage& storage)
      : storage_(storage), worker_id_(storage.StartWork()) {}
 
  BusyMarker(const BusyMarker&) = delete;
  BusyMarker& operator=(const BusyMarker&) = delete;
 
  ~BusyMarker() { storage_.StopWork(worker_id_); }
 
 private:
  BusyStorage& storage_;
  BusyStorage::WorkerId worker_id_;
};
 
}  // namespace utils::statistics
 
USERVER_NAMESPACE_END