blob: 2cf8c8c4c2eedd8e3782c06c5c087988fdc6ba9c [file] [log] [blame]
// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <lib/fit/function.h>
#include <random>
#include "src/lib/backoff/backoff.h"
namespace backoff {
// Exponential backoff. The returned backoff delay is D + r:
// D = |initial_delay| * |retry_factor| ^ N
// r = rand(0, D)
// with N denoting the number of consecutive GetNext() calls, starting at 0.
class ExponentialBackoff : public Backoff {
explicit ExponentialBackoff(fit::function<uint64_t()> seed_generator = DefaultSeedGenerator);
ExponentialBackoff(zx::duration initial_delay, uint32_t retry_factor, zx::duration max_delay,
fit::function<uint64_t()> seed_generator = DefaultSeedGenerator);
~ExponentialBackoff() override;
zx::duration GetNext() override;
void Reset() override;
static uint64_t DefaultSeedGenerator();
const zx::duration initial_delay_;
const uint32_t retry_factor_;
const zx::duration max_delay_;
// Used to prevent overflows in multiplication.
const zx::duration max_delay_divided_by_factor_;
std::default_random_engine rng_;
zx::duration next_delay_ = initial_delay_;
} // namespace backoff