EDK Configuration System Overview

The Enterprise Development Kit (EDK) extends the IDK core configuration system with cloud providers, database persistence, and offline caching capabilities for enterprise deployments.

Key Concept: Just Add the Dependency

EDK configuration providers use auto-registration. When you add a provider module to your classpath, it automatically integrates with the ConfigService. Your application code just calls:

val apiUrl = configService.getProperty("api.base.url", String::class)

The system figures out where to get the value - environment variables, Azure App Configuration, database, or property files.

Architecture

Auto-Registration

Providers register themselves automatically when:

1. Their module is on the classpath
2. Required configuration is provided (e.g., connection strings)
3. They're not explicitly disabled

How It Works

When your application starts, the PropertySourceBootstrap service:

1. Discovers all PropertySourceContribution implementations via dependency injection
2. Checks if each provider is enabled (configuration flag + required config)
3. Registers enabled providers with the appropriate ConfigService
4. Initializes providers that need async setup (cloud providers)

Enabling a Provider

Simply add the dependency and provide connection details:

Azure App Config

build.gradle.kts

dependencies {
    implementation("com.sphereon.edk:lib-conf-azure-app-config:$version")
}

Environment Variables

# Azure auto-enables when connection details are provided
export AZURE_APPCONFIG_CONNECTION_STRING="Endpoint=https://myapp.azconfig.io;..."

# Or use endpoint with managed identity
export AZURE_APPCONFIG_ENDPOINT="https://myapp.azconfig.io"

REST Config

build.gradle.kts

dependencies {
    implementation("com.sphereon.edk:lib-conf-config-rest-client:$version")
}

Environment Variables

export REST_CONFIG_BASE_URL="https://config.example.com"
export REST_CONFIG_TENANT_ID="my-tenant"
export REST_CONFIG_AUTH_API_KEY="my-api-key"

Database (VDX)

build.gradle.kts

dependencies {
    implementation("com.sphereon.vdx:vdx-conf-settings-persistence-postgresql:$version")
}

Database providers auto-register when database connection is configured.

Disabling a Provider

Disable any provider via configuration:

# Disable Azure provider
export CONFIG_PROVIDERS_AZURE_APP_CONFIG_ENABLED=false

# Disable REST provider
export CONFIG_PROVIDERS_REST_CONFIG_ENABLED=false

# Disable PostgreSQL database provider
export CONFIG_PROVIDERS_POSTGRESQL_DB_ENABLED=false

Or in properties:

config.providers.azure-app-config.enabled=false
config.providers.rest-config.enabled=false
config.providers.postgresql-db.enabled=false

Provider IDs

Each provider has a unique ID for configuration:

Provider	Provider ID	Module
Azure App Configuration	azure-app-config	lib-conf-azure-app-config
REST Config Client	rest-config	lib-conf-config-rest-client
PostgreSQL Database	postgresql-db	vdx-conf-settings-persistence-postgresql
MySQL Database	mysql-db	vdx-conf-settings-persistence-mysql
SQLite Database	sqlite-db	vdx-conf-settings-persistence-sqlite

Module Summary

Cloud Configuration Providers

Module	Description	Platform	Priority
config-rest-client	REST API client for remote configuration servers	Multiplatform	High
azure-app-config	Azure App Configuration integration	JVM	High

Database Providers (VDX)

Module	Description	Platform	Priority
vdx-conf-settings-persistence-postgresql	PostgreSQL settings storage	JVM	Medium
vdx-conf-settings-persistence-mysql	MySQL settings storage	JVM	Medium
vdx-conf-settings-persistence-sqlite	SQLite settings storage	JVM	Medium

Caching

Module	Description	Platform
config-offline-cache	Offline-capable configuration caching	Multiplatform

Priority Order

When the same key exists in multiple providers:

Priority	Provider Type	Example
1 (Highest)	Environment Variables	API_URL=...
2	System Properties	-Dapi.url=...
3	Cloud Providers	Azure, REST
4	Database Providers	PostgreSQL, MySQL
5	Property Files	application.properties
6 (Lowest)	Programmatic Defaults	MapPropertySource

This allows you to:

• Define defaults in property files or database
• Override with cloud configuration for centralized management
• Override everything with environment variables in production

Configuration Reference

Azure App Configuration

# Connection (use one)
azure.appconfig.connection-string=Endpoint=https://...;Id=...;Secret=...
azure.appconfig.endpoint=https://myapp.azconfig.io

# Key filtering
azure.appconfig.key-filter=myapp/*
azure.appconfig.key-prefix=myapp/
azure.appconfig.trim-key-prefix=true

# Label/environment
azure.appconfig.label-filter=production

# Change detection
azure.appconfig.sentinel-key=app:version
azure.appconfig.refresh-interval=30s

# Scoping
azure.appconfig.tenant-id=my-tenant

REST Config Client

# Connection
rest.config.base-url=https://config.example.com
rest.config.tenant-id=my-tenant
rest.config.profile=production

# Paths
rest.config.settings-path=/api/v1/config/settings
rest.config.refresh-path=/api/v1/config/refresh

# Authentication (choose one method)
rest.config.auth.method=API_KEY
rest.config.auth.api-key=my-api-key
rest.config.auth.api-key-header=X-API-Key

# Or Bearer token
rest.config.auth.method=BEARER_TOKEN
rest.config.auth.bearer-token=my-jwt-token

# Timeouts
rest.config.connect-timeout-ms=5000
rest.config.read-timeout-ms=30000

# Caching
rest.config.offline-cache-enabled=true

Quick Start Example

// Your application just uses ConfigService - providers are auto-registered
class MyService(
    private val configService: ConfigService
) {
    fun doSomething() {
        // This value might come from Azure, REST, database, or env vars
        // Your code doesn't need to know!
        val apiUrl = configService.getProperty("api.base.url", String::class)
            ?: throw IllegalStateException("api.base.url not configured")

        val timeout = configService.getProperty("http.timeout.ms", Int::class, 30000)
        val retryEnabled = configService.getProperty("retry.enabled", Boolean::class, true)

        // Use the configuration...
    }
}

Caching Behavior

Cloud Providers

Cloud providers use OfflineConfigCache for network resilience:

refresh() called
    │
    ├─ Network request to Azure/REST
    │    │
    │    ├─ Success
    │    │    ├─ Update in-memory store
    │    │    ├─ Persist to offline cache (disk)
    │    │    └─ Return success
    │    │
    │    └─ Failure (network error)
    │         ├─ Load from offline cache
    │         └─ Return cached data (or error if cache empty)

Database Providers

Database providers use SettingsCache for performance:

• Read: Check cache → query database → cache result
• Write: Update database → invalidate cache
• TTL: Cached entries expire automatically

Related Documentation

• Cloud Providers - Detailed REST and Azure configuration
• Offline Cache - Offline caching system details
• IDK Configuration - Core configuration concepts
• IDK Providers - Provider overview and custom providers