CConfigFile::getInstance() - Configuration Management System

Overview

CConfigFile::getInstance() implements a singleton pattern that provides centralized access to JSON-based configuration management in the DroneEngage Communication Module. It handles loading, parsing, monitoring, and updating of the main configuration file (de_comm.config.module.json).

Class Architecture

Singleton Pattern

static CConfigFile& getInstance()
{
    static CConfigFile instance; // Guaranteed to be destroyed.
                                 // Instantiated on first use.
    return instance;
}

Key Features

  • Thread-safe singleton using Scott Meyers’ implementation

  • File monitoring with automatic reload on changes

  • JSON parsing with C-style comment support

  • Nested key updates (e.g., “follow_me.quad.PID_P_X”)

  • Automatic backup before saving changes

  • Runtime configuration updates

Configuration File Structure

The system reads from de_comm.config.module.json which contains:

{
    // Module Identification
    "module_id": "MT_1",
    "unit_type": "control_unit",
    
    // Network Configuration
    "s2s_udp_listening_ip": "0.0.0.0",
    "s2s_udp_listening_port": "60000",
    "s2s_udp_packet_size": "8192",
    
    // Authentication Settings
    "auth_ip": "cloud.ardupilot.org",
    "auth_port": 19408,
    "auth_verify_ssl": false,
    "userName": "mhefny@andruav.com",
    "accessCode": "mhefny",
    
    // Unit Information
    "unitID": "drone_cairo",
    "groupID": "1",
    "unitDescription": "de_unit 1",
    
    // Connection Management
    "ping_server_rate_in_ms": 1500,
    "max_allowed_ping_delay_in_ms": 5000,
    "max_offline_count": 5,
    
    // Hardware Configuration
    "led_pins_enabled": true,
    "buzzer_pins_enabled": true,
    
    // Logging Configuration
    "logger_enabled": false,
    "logger_debug": false,
    
    // SSL Certificate (optional)
    "root_certificate_path": "./root.crt"
}

Usage Throughout the Solution

1. main.cpp - Core Initialization

de::CConfigFile& cConfigFile = de::CConfigFile::getInstance();
cConfigFile.initConfigFile(configName.c_str()); // "de_comm.config.module.json"

Values accessed:

  • module_id - Module identification for UAVOS system

  • s2s_udp_packet_size - UDP packet size for inter-module communication

  • s2s_udp_listening_ip - IP address for UDP listener

  • s2s_udp_listening_port - Port for UDP listener

  • groupID - Group identification for module registration

  • unit_type - Type of unit (control_unit/drone)

  • unitID - Unit identifier (fallback from local config)

  • unitDescription - Unit description (fallback from local config)

  • logger_enabled - Enable/disable logging system

  • logger_debug - Enable debug logging

  • led_pins_enabled - Enable LED notification pins

  • buzzer_pins_enabled - Enable buzzer notification pins

  • local_comm_server_ip - Local communication server IP (optional)

  • local_comm_server_port - Local communication server port (optional)

2. andruav_auth.cpp - Authentication System

de::CConfigFile& cConfigFile = de::CConfigFile::getInstance();
const Json_de& jsonConfig = cConfigFile.GetConfigJSON();

Values accessed:

  • auth_ip - Authentication server IP address

  • auth_port - Authentication server port

  • userName - Username for authentication

  • accessCode - Access code/password

  • auth_verify_ssl - SSL verification toggle

  • root_certificate_path - Path to SSL certificate (optional)

Usage context:

  • Building authentication URLs: https://[auth_ip]:[auth_port]/api/endpoint

  • Configuring SSL settings for HTTPS requests

  • Setting up certificate validation

3. andruav_comm_server.cpp - Remote Connection Management

de::CConfigFile& cConfigFile = de::CConfigFile::getInstance();
const Json_de& jsonConfig = cConfigFile.GetConfigJSON();

Values accessed:

  • ping_server_rate_in_ms - Ping interval in milliseconds (default: 1500ms)

  • max_allowed_ping_delay_in_ms - Maximum delay before reconnection (default: 5000ms)

  • max_offline_count - Maximum offline attempts before abort (default: 5)

Usage context:

  • Watchdog thread configuration for connection monitoring

  • Automatic reconnection logic

  • Connection health monitoring

4. andruav_comm_server_local.cpp - Local Connection Management

de::CConfigFile& cConfigFile = de::CConfigFile::getInstance();
const Json_de& jsonConfig = cConfigFile.GetConfigJSON();

Values accessed:

  • Same as remote server: ping_server_rate_in_ms, max_allowed_ping_delay_in_ms, max_offline_count

Usage context:

  • Local communication server watchdog

  • Same monitoring logic as remote but for local connections

Configuration Flow Logic

Initialization Sequence

  1. Singleton Creation: First call to getInstance() creates the instance

  2. File Loading: initConfigFile() loads and parses the JSON

  3. File Monitoring: fileUpdated() monitors for external changes

  4. Runtime Updates: updateJSON() allows dynamic configuration changes

File Monitoring Logic

bool fileUpdated() {
    auto lastWriteTime = std::filesystem::last_write_time(m_file_url);
    if (lastWriteTime == m_lastWriteTime) return false;
    m_lastWriteTime = lastWriteTime;
    return true;
}

Update Logic

The system supports nested key updates:

// Update nested value
updateJSON('{"follow_me.quad.PID_P_X": 1.5}');
// Equivalent to:
// m_ConfigJSON["follow_me"]["quad"]["PID_P_X"] = 1.5;

Error Handling

Validation Pattern

if (validateField(jsonConfig,"field_name", Json_de::value_t::type)) {
    value = jsonConfig["field_name"].get<type>();
} else {
    // Use default value or handle error
}

Fatal Errors

  • Missing required authentication fields (auth_ip, auth_port) → exit(1)

  • Missing required network fields (s2s_udp_listening_ip, s2s_udp_listening_port) → Warning + default

Graceful Degradation

  • Optional fields use defaults when missing

  • File monitoring errors logged but don’t crash

  • SSL certificate errors logged but continue with warnings

Thread Safety

  • Singleton: Thread-safe through static initialization

  • File Operations: Protected by filesystem atomicity

  • JSON Access: Read-only after initialization (except explicit updates)

  • Monitoring: File timestamp comparison is atomic

Integration Points

With CLocalConfigFile

  • CConfigFile handles global/module configuration

  • CLocalConfigFile handles instance-specific overrides

  • Local config takes precedence for certain fields (unitID, unitDescription)

With Module Manager

  • Provides network configuration for UDP databus

  • Supplies module identification for registration

  • Enables/disables hardware features (LEDs, buzzer)

With Authentication System

  • Supplies server connection parameters

  • Configures SSL/TLS settings

  • Provides user credentials

Best Practices

  1. Always validate fields before accessing to avoid runtime exceptions

  2. Use meaningful defaults for optional configuration

  3. Monitor file changes for runtime configuration updates

  4. Create backups before saving configuration changes

  5. Handle nested structures properly when updating configuration

Dependencies

  • nlohmann/json: JSON parsing and manipulation

  • std::filesystem: File monitoring and operations

  • std::stringstream: String manipulation for parsing

  • C++17: Required for filesystem support

File Locations

  • Header: src/configFile.hpp

  • Implementation: src/configFile.cpp

  • Configuration: de_comm.config.module.json

  • Backups: de_comm.config.module.json.bak_YYYYMMDD_HHMMSS

This document provides a comprehensive overview of the CConfigFile singleton pattern usage and configuration management in the DroneEngage Communication Module.