busy.hpp

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#pragma once
 
/// @file userver/utils/statistics/busy.hpp
/// @brief @copybrief utils::statistics::BusyMarker
 
#include <memory>
 
#include <userver/utils/statistics/recentperiod.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace utils::statistics {
 
/// Measure how much time we've spent in work recently in percents that
/// supports recirsive starts. Use
/// utils::statistics::BusyMarker for RAII time measures.
///
/// @snippet utils/statistics/busy_test.cpp  busy sample
class BusyStorage final {
public:
    using Duration = std::chrono::steady_clock::duration;
 
    BusyStorage(Duration epoch_duration, Duration history_period);
 
    ~BusyStorage();
 
    /// Safe to read concurrently with calling StartWork() and StopWork()
    double GetCurrentLoad() const;
 
    /// Starts the time measure, if it was not already started
    void StartWork();
 
    /// Stops the time measure if the count of StopWork() invocations matches the
    /// StartWork() invocations count.
    void StopWork() noexcept;
 
    /// Returns true if the time measure is active
    bool IsAlreadyStarted() const noexcept;
 
private:
    Duration GetNotCommittedLoad() const noexcept;
 
    struct Impl;
    std::unique_ptr<Impl> pimpl_;
};
 
/// @brief A RAII-style guard to account code block execution time in
/// utils::statistics::BusyStorage. Aware of recursive invocations in the same
/// thread.
///
/// @snippet utils/statistics/busy_test.cpp  busy sample
class BusyMarker final {
public:
    BusyMarker(BusyStorage& storage)
        : storage_(storage)
    {
        storage_.StartWork();
    }
 
    BusyMarker(const BusyMarker&) = delete;
    BusyMarker& operator=(const BusyMarker&) = delete;
 
    ~BusyMarker() { storage_.StopWork(); }
 
private:
    BusyStorage& storage_;
};
 
}  // namespace utils::statistics
 
USERVER_NAMESPACE_END