thread_pool_sample.cpp

Shows how to create a thread pool with multiple workers, enqueue a large batch of callback jobs, and use the logger system for output. This is the canonical "hello world" for thread_system with logging.

See also

thread_pool, callback_job, log_module

// BSD 3-Clause License
// Copyright (c) 2024, 🍀☀🌕🌥 🌊
// See the LICENSE file in the project root for full license information.
 
#include <iostream>
#include <memory>
#include <chrono>
 
#include "logger/core/logger.h"
#include <kcenon/thread/utils/formatter.h>
#include <kcenon/thread/core/thread_pool.h>
 
using kcenon::thread::utils::formatter;
using namespace kcenon::thread;
 
bool use_backup_ = false;
uint32_t max_lines_ = 0;
uint16_t wait_interval_ = 100;
uint32_t test_line_count_ = 1000000;
log_module::log_types file_target_ = log_module::log_types::None;
log_module::log_types console_target_ = log_module::log_types::Information;
log_module::log_types callback_target_ = log_module::log_types::None;
 
uint16_t thread_counts_ = 10;
 
auto initialize_logger() -> std::optional<std::string>
{
    log_module::set_title("thread_pool_sample");
    log_module::set_use_backup(use_backup_);
    log_module::set_max_lines(max_lines_);
    log_module::file_target(file_target_);
    log_module::console_target(console_target_);
    log_module::callback_target(callback_target_);
    // Note: This demonstrates the logger callback feature - std::cout is intentionally used here
    log_module::message_callback(
        [](const log_module::log_types& type, const std::string& datetime,
           const std::string& message)
        { std::cout << formatter::format("[{}][{}] {}\n", datetime, type, message); });
    if (wait_interval_ > 0)
    {
        log_module::set_wake_interval(std::chrono::milliseconds(wait_interval_));
    }
 
    return log_module::start();
}
 
auto create_default(const uint16_t& worker_counts)
    -> std::tuple<std::shared_ptr<thread_pool>, kcenon::common::VoidResult>
{
    std::shared_ptr<thread_pool> pool;
 
    try
    {
        pool = std::make_shared<thread_pool>();
    }
    catch (const std::bad_alloc& e)
    {
        return { nullptr, kcenon::common::error_info{
            kcenon::thread::error_code::allocation_failed,
            e.what(),
            "thread_pool_sample"} };
    }
 
    std::vector<std::unique_ptr<thread_worker>> workers;
    workers.reserve(worker_counts);
    for (uint16_t i = 0; i < worker_counts; ++i)
    {
        workers.push_back(std::make_unique<thread_worker>());
    }
 
    auto enqueue_result = pool->enqueue_batch(std::move(workers));
    if (enqueue_result.is_err())
    {
        return { nullptr, enqueue_result.error() };
    }
 
    return { pool, kcenon::common::ok() };
}
 
auto store_job(std::shared_ptr<thread_pool> thread_pool) -> kcenon::common::VoidResult
{
    std::vector<std::unique_ptr<job>> jobs;
    jobs.reserve(test_line_count_);
 
    for (auto index = 0; index < test_line_count_; ++index)
    {
        jobs.push_back(std::make_unique<callback_job>(
            [index](void) -> kcenon::common::VoidResult
            {
                log_module::write_debug("Hello, World!: {}", index);
                return kcenon::common::ok();
            }));
    }
 
    auto result = thread_pool->enqueue_batch(std::move(jobs));
    if (result.is_err())
    {
        return result.error();
    }
 
    log_module::write_sequence("enqueued jobs: {}", test_line_count_);
 
    return kcenon::common::ok();
}
 
auto main() -> int
{
    auto error_message = initialize_logger();
    if (error_message.has_value())
    {
        std::cerr << formatter::format("error starting logger: {}\n",
                                       error_message.value_or("unknown error"));
        return 0;
    }
 
    std::shared_ptr<thread_pool> thread_pool = nullptr;
    kcenon::common::VoidResult pool_init_result;
    std::tie(thread_pool, pool_init_result) = create_default(thread_counts_);
    if (pool_init_result.is_err())
    {
        log_module::write_error("error creating thread pool: {}",
                                pool_init_result.error().message);
 
        return 0;
    }
 
    log_module::write_information("created {}", thread_pool->to_string());
 
    auto store_result = store_job(thread_pool);
    if (store_result.is_err())
    {
        log_module::write_error("error storing job: {}", store_result.error().message);
 
        thread_pool.reset();
 
        return 0;
    }
 
    auto start_result = thread_pool->start();
    if (start_result.is_err())
    {
        log_module::write_error("error starting thread pool: {}",
                                start_result.error().message);
 
        thread_pool.reset();
 
        return 0;
    }
 
    log_module::write_information("started {}", thread_pool->to_string());
 
    auto stop_result = thread_pool->stop();
    if (stop_result.is_err())
    {
        log_module::write_error("error stopping thread pool: {}",
                                stop_result.error().message);
    }
 
    log_module::write_information("stopped {}", thread_pool->to_string());
 
    thread_pool.reset();
 
    log_module::stop();
 
    return 0;
}