[ADR] Implement Unified Configuration Management System

[groldan]

Decision Title

Implement Unified Configuration Management System

Status

• Proposed (under consideration)
• Accepted (decision made)
• Superseded (replaced by newer decision)
• Deprecated (no longer relevant)

Context

The library currently lacks a unified configuration system, leading to inconsistent configuration patterns across different providers and features. Users must configure each component separately with different APIs, making it difficult to manage complex deployments and apply consistent settings across multiple RangeReader instances.

Decision

Implement a centralized configuration management system that provides consistent configuration APIs, environment-based configuration loading, and hierarchical configuration merging with validation and type safety.

Problem Statement

Current configuration limitations impact usability and maintainability:

• Inconsistent configuration APIs across different providers
• No centralized configuration management for complex deployments
• Limited support for environment-based configuration
• Difficult to apply consistent settings across multiple readers
• No configuration validation or error handling
• Poor developer experience for configuration management

Considered Options

Option 1: Builder Pattern Only (Current)

Description: Continue with existing builder pattern for each component

Pros:

• Simple and familiar pattern
• Type-safe configuration
• No additional dependencies

Cons:

• Inconsistent APIs across components
• No centralized configuration management
• Difficult to share settings
• Limited environment integration

Option 2: Centralized Configuration Manager

Description: Implement unified configuration system with hierarchical settings

Pros:

• Consistent configuration experience
• Environment-based configuration support
• Configuration sharing and inheritance
• Validation and error handling
• Profile-based configuration management

Cons:

• Added complexity to the system
• Learning curve for configuration concepts
• Potential performance overhead

Option 3: External Configuration Framework

Description: Integrate with external configuration libraries (Spring Config, etc.)

Pros:

• Leverage existing mature solutions
• Rich feature set and ecosystem integration
• Proven configuration patterns

Cons:

• External dependency complexity
• May not fit library usage patterns
• Limited control over configuration behavior

Decision Rationale

Option 2 (Centralized Configuration Manager) is selected because:

• Provides consistent configuration experience across all components
• Enables environment-based configuration for different deployment scenarios
• Supports configuration sharing and inheritance for complex setups
• Maintains full control over configuration behavior and validation
• Balances functionality with library dependency minimalism

Architecture Impact

Affected Components

• Core module (configuration infrastructure)
• All provider modules (configuration integration)
• Caching layer (configuration support)
• Authentication system (configuration management)
• Performance optimizations (configuration tuning)
• API design (builder integration)
• Build system
• Documentation

Breaking Changes

• No breaking changes
• Minor breaking changes (patch release)
• Major breaking changes (major version bump)

Performance Impact

• Performance improvement expected
• Performance neutral
• May degrade performance (requires optimization)
• Unknown performance impact (requires analysis)

Security Impact

• Improves security
• Security neutral
• Potential security implications (requires review)

Implementation Plan

Phase 1: Core Configuration Infrastructure

• Design configuration API and interfaces
• Implement hierarchical configuration system
• Add environment variable and property file support
• Create configuration validation framework

Phase 2: Provider Integration

• Migrate existing builder patterns to configuration system
• Add configuration profiles for different scenarios
• Implement configuration inheritance and merging
• Add configuration change detection and hot-reload

Phase 3: Advanced Features

• Configuration encryption for sensitive values
• Configuration templating and variable substitution
• Remote configuration source support
• Configuration audit logging and change tracking

Phase 4: Developer Experience

• Configuration schema definition and validation
• IDE support and auto-completion
• Configuration documentation generation
• Migration tools for existing configurations

Dependencies

• Configuration parsing and validation framework
• Environment variable and property file processing
• Type conversion and validation utilities
• Optional encryption support for sensitive values

Effort Estimate

• Medium (1-4 weeks)

Quality Attributes Impact

Performance

Impact: Neutral
Details: Configuration overhead only during initialization, cached for runtime use

Reliability

Impact: Positive
Details: Configuration validation prevents runtime errors from misconfiguration

Security

Impact: Positive
Details: Secure handling of credentials and sensitive configuration values

Maintainability

Impact: Positive
Details: Centralized configuration management simplifies maintenance and updates

Usability

Impact: Positive
Details: Consistent configuration experience across all components

Portability

Impact: Positive
Details: Environment-based configuration enables deployment portability

Consequences

Positive Consequences

• Consistent configuration experience across all library components
• Environment-based configuration enabling different deployment scenarios
• Configuration sharing and inheritance reducing duplication
• Validation and error handling preventing runtime configuration errors
• Better integration with enterprise configuration management practices

Negative Consequences

• Additional complexity in configuration system implementation
• Learning curve for users familiar with simple builder patterns
• Potential configuration schema evolution challenges
• Additional testing complexity for configuration scenarios

Risks

• Risk: Configuration complexity discourages adoption

  • Impact: Medium
  • Probability: Low
  • Mitigation: Provide simple defaults and clear documentation

• Risk: Performance overhead from configuration processing

  • Impact: Low
  • Probability: Low
  • Mitigation: Cache processed configuration, lazy loading

Validation & Verification

How will this decision be validated?

• Proof of concept implementation
• Community feedback
• Expert review
• Production testing
• Performance benchmarks

Success Criteria

1. Consistent configuration APIs across all providers and features
2. Environment-based configuration works with zero code changes
3. Configuration validation prevents common misconfiguration errors
4. Performance overhead <1ms for configuration access

Rollback Plan

If centralized configuration proves problematic:

1. Maintain builder pattern compatibility alongside configuration system
2. Make configuration system optional via feature flags
3. Revert to builder-only approach in future release if needed

Documentation Requirements

• Architecture Decision Record (ADR-015)
• API documentation update
• Architecture documentation update
• Migration guide (if breaking changes)
• Developer guide updates

Stakeholder Impact

Library Users

Impact: Positive - Simplified configuration management with better environment support

Library Contributors

Impact: Neutral - Additional configuration infrastructure but clearer configuration patterns

Ecosystem Integration

Impact: Positive - Better integration with enterprise configuration management systems

Related Decisions

• Connected to observability framework (configuration for metrics and monitoring)
• Related to enterprise authentication (configuration for security settings)
• Dependencies on SPI provider discovery (configuration-driven provider selection)

References

• 12-Factor App Configuration
• Spring Boot Configuration
• Java Configuration Best Practices

Timeline

Target Decision Date: Q1 2025
Target Implementation Date: Q2 2025
Target Release: Version 1.1

Additional Context

Configuration System Design

// Unified configuration interface
public interface RangeReaderConfig {
    // Provider selection and configuration
    String getProvider();
    URI getUri();
    Map<String, Object> getProviderConfig();
    
    // Caching configuration
    CacheConfig getCacheConfig();
    
    // Performance configuration
    PerformanceConfig getPerformanceConfig();
    
    // Security configuration
    SecurityConfig getSecurityConfig();
}

// Configuration builder with environment support
public class RangeReaderConfigBuilder {
    public static RangeReaderConfig fromEnvironment() {
        return new EnvironmentConfigLoader().load();
    }
    
    public static RangeReaderConfig fromProperties(String resourcePath) {
        return new PropertiesConfigLoader().load(resourcePath);
    }
    
    public static RangeReaderConfig fromProfile(String profile) {
        return new ProfileConfigLoader().load(profile);
    }
}

// Usage examples
RangeReader reader = RangeReaderFactory.create(
    RangeReaderConfig.fromEnvironment()
);

RangeReader reader = RangeReaderFactory.create(
    RangeReaderConfig.fromProfile("production")
);

Environment-Based Configuration

# application.yml
rangereader:
  default:
    cache:
      memory-size: 256MB
      disk-size: 10GB
    performance:
      connection-timeout: 10s
      read-timeout: 30s
    
  profiles:
    development:
      cache:
        memory-size: 64MB
        disk-size: 1GB
      logging:
        level: DEBUG
    
    production:
      cache:
        memory-size: 1GB
        disk-size: 100GB
      performance:
        connection-pool-size: 100
      security:
        ssl-verification: strict

Configuration Validation

public class ConfigurationValidator {
    public ValidationResult validate(RangeReaderConfig config) {
        ValidationResult result = new ValidationResult();
        
        // Validate cache settings
        if (config.getCacheConfig().getMemorySize() > getMaxHeapSize()) {
            result.addError("Cache memory size exceeds available heap");
        }
        
        // Validate performance settings
        if (config.getPerformanceConfig().getConnectionTimeout().isNegative()) {
            result.addError("Connection timeout must be positive");
        }
        
        // Validate provider-specific settings
        validateProviderConfig(config.getProvider(), config.getProviderConfig(), result);
        
        return result;
    }
}

Configuration Profiles

// Profile-based configuration loading
public enum ConfigurationProfile {
    DEVELOPMENT("dev", "Development environment with debug settings"),
    TESTING("test", "Testing environment with mock services"),
    STAGING("staging", "Staging environment with production-like settings"),
    PRODUCTION("prod", "Production environment with optimized settings");
    
    public RangeReaderConfig loadConfig() {
        return ConfigurationLoader.builder()
            .profile(this)
            .environmentOverrides(true)
            .validation(ValidationLevel.STRICT)
            .load();
    }
}

// Usage
RangeReader reader = RangeReaderFactory.create(
    ConfigurationProfile.PRODUCTION.loadConfig()
);

This architectural decision establishes a foundation for consistent, maintainable configuration management that scales from simple development scenarios to complex enterprise deployments. The system should provide sensible defaults while enabling fine-grained control for advanced use cases.