#Understanding Configuration in Vidos

Vidos uses a layered configuration system that provides consistent settings across your deployment while enabling customization at multiple levels. This approach helps you manage configurations across services efficiently while maintaining flexibility and control.

#Why Layered Configuration?

A layered configuration system enables you to:

• Ensure all services start with secure, working settings
• Share common configurations across multiple services
• Customize specific instances without affecting others
• Maintain configurations efficiently at scale

#How Configuration Works

#The Three Layers

Vidos builds configurations using three distinct layers:

1. Core Configuration

   • Provided by Vidos
   • Contains all required settings
   • Cannot be modified
   • Ensures service stability

2. Custom Configuration

   • Reusable configuration sets
   • Applied to multiple service instances
   • Specifies only changed values
   • Overrides core settings

3. Inline Configuration

   • Instance-specific settings
   • Affects only one service instance
   • Specifies only changed values
   • Overrides previous layers

#Layer Composition

Here's how these layers combine using a CORS (Cross-Origin Resource Sharing) configuration example:

1. Core Configuration

   {
       "cors": {
           "allowHeaders": [],
           "allowMethods": ["GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS"],
           "credentials": false,
           "enabled": false,
           "exposeHeaders": [],
           "maxAge": 86400,
           "origin": ["*"]
       }
   }

2. Custom Configuration

   {
       "cors": {
           "enabled": true,
           "origin": ["https://app.example.com", "https://api.example.com"],
           "credentials": true
       }
   }

   After applying custom configuration:

   {
     "cors": {
       "allowHeaders": [],                    # ⬅ From core configuration
       "allowMethods": [                      # ⬅ From core configuration
         "GET",
         "POST",
         "PUT",
         "PATCH",
         "DELETE",
         "OPTIONS"
       ],
       "credentials": true,                   # ⬅ From custom configuration
       "enabled": true,                       # ⬅ From custom configuration
       "exposeHeaders": [],                   # ⬅ From core configuration
       "maxAge": 86400,                       # ⬅ From core configuration
       "origin": [                            # ⬅ From custom configuration
         "https://app.example.com",
         "https://api.example.com"
       ]
     }
   }

3. Inline Configuration

   {
       "cors": {
           "allowHeaders": ["Content-Type", "Authorization"],
           "origin": ["https://test.example.com"]
       }
   }

   Final configuration:

   {
     "cors": {
       "allowHeaders": [                      # ⬅ From inline configuration
         "Content-Type",
         "Authorization"
       ],
       "allowMethods": [                      # ⬅ From core configuration
         "GET",
         "POST",
         "PUT",
         "PATCH",
         "DELETE",
         "OPTIONS"
       ],
       "credentials": true,                   # ⬅ From custom configuration
       "enabled": true,                       # ⬅ From custom configuration
       "exposeHeaders": [],                   # ⬅ From core configuration
       "maxAge": 86400,                       # ⬅ From core configuration
       "origin": [                            # ⬅ From inline configuration
         "https://test.example.com"
       ]
     }
   }

#Key Concepts

1. Layer Application Order

   • Core configuration establishes base settings
   • Custom configuration provides shared overrides
   • Inline configuration sets instance-specific values

2. Configuration Scope

   • Custom configurations are reusable across instances
   • Inline configurations apply to single instances
   • Each layer can override previous layer values

3. Partial Configurations

   • Override configurations specify only changed values
   • Unspecified values inherit from previous layers
   • All settings maintain a value through inheritance

#Related Documentation

• Service instances: See Instances Guide
• Regional configuration: See Regions Guide