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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.
#ifndef INCLUDED_SRC_BUILDTOOL_COMMON_RETRY_PARAMETERS_HPP
#define INCLUDED_SRC_BUILDTOOL_COMMON_RETRY_PARAMETERS_HPP
#include <mutex>
#include <optional>
#include <random>
#include <string>
#include "fmt/core.h"
#include "src/buildtool/logging/log_level.hpp"
#include "src/utils/cpp/expected.hpp"
inline constexpr unsigned int kDefaultInitialBackoffSeconds{1};
inline constexpr unsigned int kDefaultMaxBackoffSeconds{60};
inline constexpr unsigned int kDefaultAttempts{1};
inline constexpr auto kRetryLogLevel = LogLevel::Progress;
class RetryConfig final {
public:
class Builder;
RetryConfig() = default;
[[nodiscard]] auto GetMaxAttempts() const noexcept -> unsigned int {
return attempts_;
}
/// \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 distribute the workload.
[[nodiscard]] auto GetSleepTimeSeconds(unsigned int attempt) const noexcept
-> unsigned int {
auto backoff = initial_backoff_seconds_;
// 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_seconds_) {
backoff = max_backoff_seconds_;
break;
}
}
return backoff + Jitter(backoff);
}
private:
unsigned int const initial_backoff_seconds_ = kDefaultInitialBackoffSeconds;
unsigned int const max_backoff_seconds_ = kDefaultMaxBackoffSeconds;
unsigned int const attempts_ = kDefaultAttempts;
RetryConfig(unsigned int initial_backoff_seconds,
unsigned int max_backoff_seconds,
unsigned int attempts)
: initial_backoff_seconds_{initial_backoff_seconds},
max_backoff_seconds_{max_backoff_seconds},
attempts_{attempts} {}
using dist_type = std::uniform_int_distribution<std::mt19937::result_type>;
[[nodiscard]] static auto Jitter(unsigned int backoff) noexcept ->
typename dist_type::result_type {
static std::mutex mutex;
static std::mt19937 rng{std::random_device{}()};
try {
dist_type dist{0, 3UL * backoff};
std::unique_lock lock(mutex);
return dist(rng);
} catch (...) {
return 0;
}
}
};
class RetryConfig::Builder final {
public:
auto SetInitialBackoffSeconds(std::optional<unsigned int> x) noexcept
-> Builder& {
initial_backoff_seconds_ = x;
return *this;
}
auto SetMaxBackoffSeconds(std::optional<unsigned int> x) noexcept
-> Builder& {
max_backoff_seconds_ = x;
return *this;
}
auto SetMaxAttempts(std::optional<unsigned int> x) noexcept -> Builder& {
attempts_ = x;
return *this;
}
[[nodiscard]] auto Build() const noexcept
-> expected<RetryConfig, std::string> {
unsigned int initial_backoff_seconds = kDefaultInitialBackoffSeconds;
if (initial_backoff_seconds_.has_value()) {
if (*initial_backoff_seconds_ < 1) {
return unexpected{
fmt::format("Invalid initial amount of seconds provided: "
"{}.\nValue must be strictly greater than 0.",
*initial_backoff_seconds_)};
}
initial_backoff_seconds = *initial_backoff_seconds_;
}
unsigned int max_backoff_seconds = kDefaultMaxBackoffSeconds;
if (max_backoff_seconds_.has_value()) {
if (*max_backoff_seconds_ < 1) {
return unexpected{
fmt::format("Invalid max backoff provided: {}.\nValue must "
"be strictly greater than 0.",
*max_backoff_seconds_)};
}
max_backoff_seconds = *max_backoff_seconds_;
}
unsigned int attempts = kDefaultAttempts;
if (attempts_.has_value()) {
if (*attempts_ < 1) {
return unexpected{
fmt::format("Invalid max number of attempts provided: "
"{}.\nValue must be strictly greater than 0.",
*attempts_)};
}
attempts = *attempts_;
}
return RetryConfig(
initial_backoff_seconds, max_backoff_seconds, attempts);
}
private:
std::optional<unsigned int> initial_backoff_seconds_;
std::optional<unsigned int> max_backoff_seconds_;
std::optional<unsigned int> attempts_;
};
#endif // INCLUDED_SRC_BUILDTOOL_COMMON_RETRY_PARAMETERS_HPP
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