periodic_worker.hpp

/*
    asynchrony-lib : Add asynchrony to your apps
 
    BSD 3-Clause License
 
    Copyright (c) 2021, Siddiq Software LLC
    All rights reserved.
 
    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are met:
 
    1. Redistributions of source code must retain the above copyright notice, this
       list of conditions and the following disclaimer.
 
    2. Redistributions in binary form must reproduce the above copyright notice,
       this list of conditions and the following disclaimer in the documentation
       and/or other materials provided with the distribution.
 
    3. Neither the name of the copyright holder nor the names of its
       contributors may be used to endorse or promote products derived from
       this software without specific prior written permission.
 
    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
    FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
    DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
#pragma once
#include <siddiqsoft/RunOnEnd.hpp>
#ifndef PERIODIC_WORKER_HPP
#define PERIODIC_WORKER_HPP
 
 
#include <iostream>
#include <functional>
#include <memory>
#include <thread>
#include <mutex>
#include <shared_mutex>
#include <deque>
#include <semaphore>
#include <stop_token>
#include <utility>
#include <exception>
#include <source_location>
#include <atomic>
 
#if defined(_Linux_) || defined(__linux__) || defined(__linux) || (defined(__APPLE__) && defined(__MACH__))
#include <pthread.h>
#elif defined(_WIN32) || defined(WIN32) || defined(_WIN64) || defined(WIN64)
#include <windows.h>
#include <processthreadsapi.h>
#endif
 
#include "private/common.hpp"
 
namespace siddiqsoft
{
    template <int Pri = 0>
        requires((Pri >= -10) && (Pri <= 10))
    struct periodic_worker
    {
        static constexpr std::chrono::milliseconds DEFAULT_WAIT_FOR_NEXT_ITEM_MS {1500};
 
    public:
        periodic_worker(periodic_worker&) = delete;
        
        auto& operator=(periodic_worker&) = delete;
        
        periodic_worker(periodic_worker&&) = delete;
        
        auto& operator=(periodic_worker&&) = delete;
 

        ~periodic_worker()
        {
#if defined(DEBUG) || defined(_DEBUG)
            std::cerr << std::format(
                    "Shutting down periodic worker [{}] with outstanding callbacks [{}] and total invoke count [{}]\n",
                    threadName,
                    outstandingCallback.load(std::memory_order_acquire),
                    invokeCounter.load(std::memory_order_acquire));
#endif
 
            // This is critical step since we wait on the semaphore for a long time (keeps threads suspended) and if we do not
            // decrease this interval then the shutdown will be quite delayed.
            // Use atomic store with release semantics to safely modify invokePeriod from destructor
            invokePeriod.store(std::chrono::microseconds(0), std::memory_order_release);
            // Empty signal to get our thread to wake up
            signal.release();
 
#if defined(DEBUG) || defined(_DEBUG)
            std::cerr << std::format("Signaled shutdown for periodic worker [{}], waiting for thread to join...\n", threadName);
#endif
 
            try {
                // Notify the thread to stop.. and wait for a bit.. and then instead of joining we should just let the jthread
                // destroy. Ask thread to shutdown and if joinable.. join.
                processor.request_stop();
                std::this_thread::sleep_for(std::chrono::milliseconds(100));
                // if (processor.joinable()) processor.join();
            }
            catch (const std::exception& ex) {
                std::cerr << std::format("Exception while shutting down periodic worker [{}]: {}", threadName, ex.what());
            }
 
#if defined(DEBUG) || defined(_DEBUG)
            std::cerr << std::format("End of destructor for periodic worker [{}], waiting for thread to join...\n", threadName);
#endif
        }

        void forceCleanupTerminate(const std::source_location& sl = std::source_location::current())
        {
            std::call_once(flag_forceCleanupTerminate, [&]() {
                try {
                    // Notify the thread to stop.. and wait a bit before forceful termination
                    processor.request_stop();
                    std::this_thread::sleep_for(std::chrono::milliseconds(100));
#if defined(_Linux_) || defined(__linux__) || defined(__linux) || (defined(__APPLE__) && defined(__MACH__))
                    auto nativeHandle = processor.native_handle();
                    std::cerr << std::format(
                            "forceCleanupTerminate - WARNING!! Calling native thread shutdown; only perform this when app is "
                            "ending! from: {}:{}",
                            sl.file_name(),
                            sl.line());
                    pthread_cancel(nativeHandle);
                    processor.detach();
#elif defined(_WIN32) || defined(WIN32) || defined(_WIN64) || defined(WIN64)
                auto nativeHandle = processor.native_handle();
                std::cerr << std::format(
                             "forceCleanupTerminate - WARNING!! Calling native thread shutdown; only perform this when app is "
                             "ending! from: {}:{}",
                             sl.file_name(),
                             sl.line());
                TerminateThread(nativeHandle, 0);
                processor.detach();
#endif
                }
                catch (const std::exception& ex) {
                    std::cerr << std::format("forceCleanupTerminate - Exception while shutting down worker: {}", ex.what());
                }
            });
        }

        periodic_worker(std::function<void()>     c,
                        std::chrono::microseconds interval,
                        std::string               name = {"anonymous-periodic-worker"})
            : callback(std::move(c))
            , invokePeriod(interval)
            , threadName(std::move(name))
        {
        }
 
 
#if defined(NLOHMANN_JSON_VERSION_MAJOR)
        nlohmann::json toJson() const
        {
            using namespace std;
 
            return {{"_typver"s, "siddiqsoft.asynchrony-lib.periodic_worker/0.10"s},
                    {"threadName", threadName},
                    {"outstandingCallbacks", outstandingCallback.load(std::memory_order_acquire)},
                    {"invokeCounter"s, invokeCounter.load(std::memory_order_acquire)},
                    {"threadPriority"s, Pri},
                    {"waitInterval"s, invokePeriod.load(std::memory_order_acquire).count()}};
        }
#endif
 
    private:
        std::once_flag flag_forceCleanupTerminate {};

        std::atomic_uint outstandingCallback {0};
        
        std::string threadName {"anonymous-periodic-worker"};
        
        std::atomic_uint64_t invokeCounter {0};
        
        std::counting_semaphore<1> signal {0};
        
        std::atomic<std::chrono::microseconds> invokePeriod {std::chrono::milliseconds(1500)};
        
        std::function<void()> callback;
        
        std::jthread processor {[&](std::stop_token st) {
#if defined(WIN64) || defined(_WIN64) || defined(WIN32) || defined(_WIN32)
            // Set the thread priority if possible
            if constexpr (Pri != 0) SetThreadPriority(GetCurrentThread(), Pri);
#endif
 
            while (!st.stop_requested()) {
                try {
                    // This will wait until our period and return.
                    // We do not care about the return from try_acquire_for..
                    // We're using it as an efficient "wait" facility for period.
                    // Load invokePeriod atomically with acquire semantics
                    auto _ = signal.try_acquire_for(invokePeriod.load(std::memory_order_acquire));
 
                    if (!st.stop_requested()) {
                        auto decrementOutstandingCallback = siddiqsoft::RunOnEnd {[&] {
                            // Decrement outstanding callback
                            outstandingCallback.fetch_sub(1, std::memory_order_release);
                        }};
 
                        // Increment outstanding callback with release semantics
                        outstandingCallback.fetch_add(1, std::memory_order_release);
                        try {
                            // Delegate to the callback outside the lock
                            if (callback) callback();
                            invokeCounter.fetch_add(1, std::memory_order_release);
                        }
                        catch (const std::exception& ex) {
                            // We swallow exceptions from the callback to avoid thread termination and log it if needed.
                            std::cerr << std::format("Ignoring Exception (inner) in periodic_worker callback: {}", ex.what());
                        }
                    }
                }
                catch (const std::exception& ex) {
                    // We swallow exceptions from the callback to avoid thread termination and log it if needed.
                    std::cerr << std::format("Ignoring Exception (outer) in periodic_worker callback: {}", ex.what());
                }
            } // while ..continue until we're asked to stop
        }};
    };
 
#if defined(NLOHMANN_JSON_VERSION_MAJOR)
    template <int Pri = 0>
    static void to_json(nlohmann::json& dest, const siddiqsoft::periodic_worker<Pri>& src)
    {
        dest = src.toJson();
    }
#endif
 
} // namespace siddiqsoft
#endif // PERIODIC_WORKER_HPP