flags

README

Configuration Flags Example

This example demonstrates how to use the configuration library with command-line flags to specify configuration sources.

Features

• ✅ Command-line Flag Support - Use -config flag to specify configuration URI
• ✅ Default Fallback - Fallback to default URI if no flag provided
• ✅ Multiple Sources - Works with files, Redis, HTTP, WebSocket sources
• ✅ Custom Flag Names - Support for custom flag names via NewWithFlagsNamed
• ✅ Empty Value Handling - Uses default if flag is provided but empty

Quick Start

1. Run with default configuration:

   go run main.go
   # Uses: file://./config.json
   

2. Run with custom file:

   go run main.go -config file://./prod-config.json
   # Uses: file://./prod-config.json
   

3. Run with Redis configuration:

   # First setup Redis with configuration
   redis-cli SET app-config '{"server":{"host":"redis-app","port":8080,"debug":false},"database":{"url":"redis://localhost:6379/0","max_connections":20}}'
   
   # Run with Redis source
   go run main.go -config "redis://localhost:6379/app-config?content-type=application/json"
   

4. Run with HTTP configuration:

   go run main.go -config "https://config-server.example.com/app-config.json"
   

API Usage

Basic Flag Support

// Uses default flag name "config"
loader := conf.NewWithFlags[Config]("file://./default-config.json")

Custom Flag Name

// Uses custom flag name "app-config"
loader := conf.NewWithFlagsNamed[Config]("app-config", "file://./default-config.json")

Command Line Examples

# Default configuration
./app

# File-based configuration
./app -config file://./config.json
./app -config file:///absolute/path/to/config.yaml

# Redis configuration
./app -config "redis://localhost:6379/app-config?content-type=application/json"
./app -config "redis://localhost:6379/settings?db=1&content-type=application/json#database"

# HTTP configuration  
./app -config "https://config-server/app.json?timeout=30s"
./app -config "http://localhost:8080/config.yaml"

# WebSocket configuration
./app -config "wss://realtime-config.example.com/config?ping_interval=30s"

# Custom flag name
./app -app-config file://./app.toml

Configuration Structure

The example uses this configuration structure:

{
  "server": {
    "host": "localhost",
    "port": 8080,
    "debug": true
  },
  "database": {
    "url": "postgresql://localhost:5432/myapp", 
    "max_connections": 10
  }
}

Expected Output

🚀 Configuration Flags Example
==============================
💡 Usage examples:
  go run main.go                                    # Uses default: file://./config.json
  go run main.go -config file://./prod-config.json  # Uses specified file
  go run main.go -config redis://localhost:6379/app # Uses Redis configuration

✅ Configuration loaded successfully!
🖥️  Server Configuration:
   📍 Host: localhost
   🔌 Port: 8080
   🐛 Debug: true
🗄️  Database Configuration:
   🔗 URL: postgresql://localhost:5432/myapp
   📊 Max Connections: 10

Benefits

1. Flexibility: Switch between different configuration sources without code changes
2. Environment Support: Use different configs for dev/staging/prod environments
3. Deployment Friendly: Easy to configure in containers, systemd services, etc.
4. Backward Compatible: Falls back to default if no flag provided
5. Validation: Built-in URI validation and error handling

Integration Examples

Docker

ENTRYPOINT ["./app", "-config", "redis://redis:6379/app-config?content-type=application/json"]

Systemd Service

[Unit]
Description=My Application
After=network.target

[Service]
ExecStart=/usr/local/bin/app -config file:///etc/myapp/config.json
Restart=always
User=myapp

[Install]
WantedBy=multi-user.target

Kubernetes

apiVersion: apps/v1
kind: Deployment
spec:
  template:
    spec:
      containers:
      - name: app
        image: myapp:latest
        command: ["./app"]
        args: ["-config", "redis://redis-service:6379/app-config?content-type=application/json"]

Troubleshooting

1. "flag provided but not defined" error:

   • Make sure to call NewWithFlags before accessing any flags
   • Avoid calling flag.Parse() manually in your application

2. "Failed to load configuration" error:

   • Verify the configuration URI is accessible
   • Check if the configuration source contains valid data
   • Ensure required decoders are imported (e.g., _ "github.com/sower-proxy/conf/decoder/json")

3. Flag not recognized:

   • Make sure you're using the correct flag name (-config by default)
   • Use NewWithFlagsNamed for custom flag names