typed_thread_pool_sample.cpp

Demonstrates priority scheduling with the typed_thread_pool. Workers are assigned to RealTime, Batch, or Background priority lanes, and jobs are routed to matching workers automatically.

See also

typed_thread_pool, typed_thread_worker, callback_typed_job, job_types

// 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 <thread>
 
#include "logger/core/logger.h"
#include <kcenon/thread/utils/formatter.h>
#include <kcenon/thread/impl/typed_pool/typed_thread_pool.h>
 
#include <format>
 
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 high_priority_workers_ = 3;
uint16_t normal_priority_workers_ = 2;
uint16_t low_priority_workers_ = 1;
 
auto initialize_logger() -> std::optional<std::string>
{
    log_module::set_title("typed_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& high_priority_workers,
                    const uint16_t& normal_priority_workers,
                    const uint16_t& low_priority_workers)
    -> std::tuple<std::shared_ptr<typed_thread_pool>, std::optional<std::string>>
{
    std::shared_ptr<typed_thread_pool> pool;
 
    try
    {
        pool = std::make_shared<typed_thread_pool>();
    }
    catch (const std::bad_alloc& e)
    {
        return { nullptr, std::string(e.what()) };
    }
 
    std::optional<std::string> error_message = std::nullopt;
 
    std::vector<std::unique_ptr<typed_thread_worker>> workers;
    workers.reserve(high_priority_workers + normal_priority_workers + low_priority_workers);
    for (uint16_t i = 0; i < high_priority_workers; ++i)
    {
        workers.push_back(std::make_unique<typed_thread_worker>(
            std::vector<job_types>{ job_types::RealTime }, "high priority worker"));
    }
 
    for (uint16_t i = 0; i < normal_priority_workers; ++i)
    {
        workers.push_back(std::make_unique<typed_thread_worker>(
            std::vector<job_types>{ job_types::Batch }, "normal priority worker"));
    }
 
    for (uint16_t i = 0; i < low_priority_workers; ++i)
    {
        workers.push_back(std::make_unique<typed_thread_worker>(
            std::vector<job_types>{ job_types::Background }, "low priority worker"));
    }
 
    auto enqueue_result = pool->enqueue_batch(std::move(workers));
    if (enqueue_result.is_err())
    {
        return { nullptr, formatter::format("cannot enqueue to workers: {}",
                                            enqueue_result.error().message) };
    }
 
    return { pool, std::nullopt };
}
 
auto store_job(std::shared_ptr<typed_thread_pool> thread_pool) -> std::optional<std::string>
{
    int target = 0;
 
    std::vector<std::unique_ptr<typed_job>> jobs;
    jobs.reserve(test_line_count_);
 
    for (auto index = 0; index < test_line_count_; ++index)
    {
        target = index % 3;
        jobs.push_back(std::make_unique<callback_typed_job>(
            [target](void) -> kcenon::common::VoidResult
            {
                log_module::write_debug("Hello, World!: {} priority", target);
                return kcenon::common::ok();
            },
            static_cast<job_types>(target)));
    }
 
    auto enqueue_result = thread_pool->enqueue_batch(std::move(jobs));
    if (enqueue_result.is_err())
    {
        return formatter::format("error enqueuing jobs: {}",
                                 enqueue_result.error().message);
    }
 
    log_module::write_sequence("enqueued jobs: {}", test_line_count_);
 
    return std::nullopt;
}
 
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<typed_thread_pool> thread_pool = nullptr;
    std::tie(thread_pool, error_message)
        = create_default(high_priority_workers_, normal_priority_workers_, low_priority_workers_);
    if (error_message.has_value())
    {
        log_module::write_error("error creating thread pool: {}",
                                error_message.value_or("unknown error"));
 
        return 0;
    }
 
    log_module::write_information("created {}", thread_pool->to_string());
 
    error_message = store_job(thread_pool);
    if (error_message.has_value())
    {
        log_module::write_error("error storing job: {}", error_message.value_or("unknown error"));
 
        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;
}