config_watcher_example.cpp

Demonstrates configuration loading and hot-reload with config_watcher.

Demonstrates configuration loading and hot-reload with config_watcher.Shows unified_config structure, config_watcher file monitoring with change callbacks, and config snapshot history.

See also

kcenon::common::config_watcher

kcenon::common::unified_config

// BSD 3-Clause License
// Copyright (c) 2021-2025, 🍀☀🌕🌥 🌊
// See the LICENSE file in the project root for full license information.
 
 
#include <cstring>
 
#include <kcenon/common/config/unified_config.h>
#include <kcenon/common/config/config_watcher.h>
 
#include <chrono>
#include <fstream>
#include <iostream>
#include <string>
#include <thread>
 
using namespace kcenon::common;
using namespace kcenon::common::config;
 
int main()
{
    std::cout << "=== Config Watcher Example ===\n\n";
 
    // Create a sample config file
    const std::string config_path = "example_config.yaml";
    {
        std::ofstream f(config_path);
        f << "thread:\n"
          << "  pool_size: 4\n"
          << "  queue_type: adaptive\n"
          << "logger:\n"
          << "  level: info\n"
          << "monitoring:\n"
          << "  enabled: true\n"
          << "  metrics_interval: 30\n";
    }
 
    // Create watcher with history of 5 snapshots
    std::cout << "1. Creating config watcher for '" << config_path << "'...\n";
    config_watcher watcher(config_path, 5);
 
    // Register change callback
    watcher.on_change(
        [](const unified_config& old_cfg, const unified_config& new_cfg)
        {
            std::cout << "\n   [Change detected]\n";
            std::cout << "   Old pool_size: " << old_cfg.thread.pool_size << "\n";
            std::cout << "   New pool_size: " << new_cfg.thread.pool_size << "\n";
        });
 
    // Register error callback
    watcher.on_error([](const std::string& error)
                     { std::cerr << "   [Config error] " << error << "\n"; });
 
    // Start watching
    std::cout << "\n2. Starting file watcher...\n";
    auto start_result = watcher.start();
    if (start_result.is_ok())
    {
        std::cout << "   Watcher running = " << (watcher.is_running() ? "true" : "false") << "\n";
    }
    else
    {
        std::cout << "   Watcher start skipped (platform may not support file watching in this "
                     "environment)\n";
    }
 
    // Simulate a config change
    std::cout << "\n3. Modifying config file...\n";
    {
        std::ofstream f(config_path);
        f << "thread:\n"
          << "  pool_size: 8\n"
          << "  queue_type: lock_free\n"
          << "logger:\n"
          << "  level: debug\n"
          << "monitoring:\n"
          << "  enabled: true\n"
          << "  metrics_interval: 10\n";
    }
 
    // Give the watcher time to detect the change
    std::this_thread::sleep_for(std::chrono::milliseconds(500));
 
    // Manual reload
    std::cout << "\n4. Manual reload...\n";
    auto reload_result = watcher.reload();
    std::cout << "   Reload: " << (reload_result.is_ok() ? "success" : "skipped") << "\n";
 
    // Stop watching
    std::cout << "\n5. Stopping watcher...\n";
    watcher.stop();
    std::cout << "   Watcher running = " << (watcher.is_running() ? "true" : "false") << "\n";
 
    // Cleanup
    std::remove(config_path.c_str());
 
    std::cout << "\nDone.\n";
    return 0;
}