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#pragma once
#include <util/datetime/base.h>
#include <util/random/normal.h>
#include <util/system/event.h>
#include <atomic>
namespace NTvmAuth {
// https://habr.com/ru/post/227225/
class TExponentialBackoff {
public:
struct TSettings {
TDuration Min;
TDuration Max;
double Factor = 1.001;
double Jitter = 0;
bool operator==(const TSettings& o) const {
return Min == o.Min &&
Max == o.Max &&
Factor == o.Factor &&
Jitter == o.Jitter;
}
};
TExponentialBackoff(const TSettings& settings, bool isEnabled = true)
: CurrentValue_(settings.Min)
, IsEnabled_(isEnabled)
{
UpdateSettings(settings);
}
void UpdateSettings(const TSettings& settings) {
Y_ENSURE(settings.Factor > 1, "factor=" << settings.Factor << ". Should be > 1");
Y_ENSURE(settings.Jitter >= 0 && settings.Jitter < 1, "jitter should be in range [0, 1)");
Min_ = settings.Min;
Max_ = settings.Max;
Factor_ = settings.Factor;
Jitter_ = settings.Jitter;
}
TDuration Increase() {
CurrentValue_ = std::min(CurrentValue_ * Factor_, Max_);
double rnd = StdNormalRandom<double>();
const bool isNegative = rnd < 0;
rnd = std::abs(rnd);
const TDuration diff = rnd * Jitter_ * CurrentValue_;
if (isNegative) {
CurrentValue_ -= diff;
} else {
CurrentValue_ += diff;
}
return CurrentValue_;
}
TDuration Decrease() {
CurrentValue_ = std::max(CurrentValue_ / Factor_, Min_);
return CurrentValue_;
}
void Sleep(TDuration add = TDuration()) {
if (IsEnabled_.load(std::memory_order_relaxed)) {
Ev_.WaitT(CurrentValue_ + add);
}
}
void Interrupt() {
Ev_.Signal();
}
TDuration GetCurrentValue() const {
return CurrentValue_;
}
void SetEnabled(bool val) {
IsEnabled_.store(val);
}
private:
TDuration Min_;
TDuration Max_;
double Factor_;
double Jitter_;
TDuration CurrentValue_;
std::atomic_bool IsEnabled_;
TAutoEvent Ev_;
};
}
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