retry_strategy.hpp

/* -*- mode: c++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * Copyright (C) 2026 Marco Craveiro <marco.craveiro@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 3 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51 Franklin
 * Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 */
#ifndef ORES_UTILITY_CONCURRENCY_RETRY_STRATEGY_HPP
#define ORES_UTILITY_CONCURRENCY_RETRY_STRATEGY_HPP
 
#include <algorithm>
#include <chrono>
 
namespace ores::utility::concurrency {
 
class retry_strategy {
public:
    struct config {
        std::chrono::seconds initial_delay{5};
        std::chrono::seconds max_delay{300};      
        std::chrono::seconds reset_threshold{60}; 
    };
 
    retry_strategy() = default;
    explicit retry_strategy(config cfg) : config_(cfg) {}
 
    void on_start() {
        last_start_ = std::chrono::steady_clock::now();
    }
 
    std::chrono::seconds on_failure() {
        const auto uptime = std::chrono::steady_clock::now() - last_start_;
        if (uptime >= config_.reset_threshold)
            count_ = 0;
 
        const auto delay = compute_delay();
        ++count_;
        return delay;
    }
 
    bool exceeded(int max) const { return count_ >= max; }
 
    int failure_count() const { return count_; }
 
    void set_failure_count(int n) { count_ = n; }
 
    void reset() {
        count_ = 0;
        last_start_ = {};
    }
 
private:
    std::chrono::seconds compute_delay() const {
        // Cap exponent at 6: initial(5) * 2^6 = 320s > max(300s), so the
        // min() clamp always applies from failure 6 onwards.
        const int exp = std::min(count_, 6);
        const auto delay = std::chrono::seconds(
            config_.initial_delay.count() * (1 << exp));
        return std::min(delay, config_.max_delay);
    }
 
    config config_{};
    int count_ = 0;
    std::chrono::steady_clock::time_point last_start_{};
};
 
} // namespace ores::utility::concurrency
 
#endif