1 files changed, 94 insertions, 0 deletions
diff --git a/library/cpp/tvmauth/client/misc/exponential_backoff.h b/library/cpp/tvmauth/client/misc/exponential_backoff.h
new file mode 100644
index 0000000000..89a7a3c8ad
--- /dev/null
+++ b/library/cpp/tvmauth/client/misc/exponential_backoff.h
@@ -0,0 +1,94 @@
+#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_;
+    };
+}