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// Copyright 2023 Huawei Cloud Computing Technology Co., Ltd.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <mutex>
#include <random>
#include "src/buildtool/logging/log_level.hpp"
#include "src/buildtool/logging/logger.hpp"
constexpr unsigned int kDefaultInitialBackoffSeconds{1};
constexpr unsigned int kDefaultMaxBackoffSeconds{60};
constexpr unsigned int kDefaultAttempts{1};
constexpr auto kRetryLogLevel = LogLevel::Progress;
class Retry {
using dist_type = std::uniform_int_distribution<std::mt19937::result_type>;
public:
Retry() = default;
[[nodiscard]] static auto Instance() -> Retry& {
static Retry instance{};
return instance;
}
[[nodiscard]] static auto SetInitialBackoffSeconds(unsigned int x) noexcept
-> bool {
if (x < 1) {
Logger::Log(
LogLevel::Error,
"Invalid initial amount of seconds provided: {}. Value must "
"be strictly greater than 0.",
x);
return false;
}
Instance().initial_backoff_seconds_ = x;
return true;
}
[[nodiscard]] static auto SetMaxBackoffSeconds(unsigned int x) noexcept
-> bool {
if (x < 1) {
Logger::Log(LogLevel::Error,
"Invalid max backoff provided: {}. Value must be "
"strictly greater than 0.",
x);
return false;
}
Instance().max_backoff_seconds_ = x;
return true;
}
[[nodiscard]] static auto GetMaxBackoffSeconds() noexcept -> unsigned int {
return Instance().max_backoff_seconds_;
}
[[nodiscard]] static auto SetMaxAttempts(unsigned int x) noexcept -> bool {
if (x < 1) {
Logger::Log(LogLevel::Error,
"Invalid number of max number of attempts provided: "
"{}. Value must be strictly greater than 0",
x);
return false;
}
Instance().attempts_ = x;
return true;
}
[[nodiscard]] static auto GetInitialBackoffSeconds() noexcept
-> unsigned int {
return Instance().initial_backoff_seconds_;
}
[[nodiscard]] static auto GetMaxAttempts() noexcept -> unsigned int {
return Instance().attempts_;
}
[[nodiscard]] static auto Jitter(unsigned int backoff) noexcept ->
typename dist_type::result_type {
auto& inst = Instance();
try {
dist_type dist{0, backoff * 3};
std::unique_lock lock(inst.mutex_);
return dist(inst.rng_);
} catch (...) {
return 0;
}
}
/// \brief The waiting time is exponentially increased at each \p attempt
/// until it exceeds max_backoff_seconds.
///
/// To avoid overloading of the reachable resources, a jitter (aka, random
/// value) is added to distributed the workload.
[[nodiscard]] static auto GetSleepTimeSeconds(unsigned int attempt) noexcept
-> unsigned int {
auto backoff = Retry::GetInitialBackoffSeconds();
auto const& max_backoff = Retry::GetMaxBackoffSeconds();
// on the first attempt, we don't double the backoff time
// also we do it in a for loop to avoid overflow
for (auto x = 1U; x < attempt; ++x) {
backoff <<= 1U;
if (backoff >= max_backoff) {
backoff = max_backoff;
break;
}
}
return backoff + Retry::Jitter(backoff);
}
private:
unsigned int initial_backoff_seconds_{kDefaultInitialBackoffSeconds};
unsigned int max_backoff_seconds_{kDefaultMaxBackoffSeconds};
unsigned int attempts_{kDefaultAttempts};
LogLevel retry_log_level_{kRetryLogLevel};
std::mutex mutex_;
std::random_device dev_;
std::mt19937 rng_{dev_()};
};
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