151 lines
3.8 KiB
Markdown
151 lines
3.8 KiB
Markdown
# Use Viper for configuration management
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* Status: Accepted
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* Deciders: Gabriel Radureau, AI Agent
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* Date: 2026-04-03
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## Context and Problem Statement
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We needed a configuration management solution for dance-lessons-coach that provides:
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- Support for multiple configuration sources (files, environment variables, defaults)
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- Configuration validation
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- Type-safe configuration loading
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- Hot reloading capabilities
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- Good error handling and reporting
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## Decision Drivers
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* Need for flexible configuration from multiple sources
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* Desire for configuration validation
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* Requirement for type-safe access to configuration
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* Need for environment-specific configurations
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* Desire for good error messages
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## Considered Options
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* Viper - Popular configuration library with many features
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* Koanf - Lightweight but powerful
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* envconfig - Simple environment variable loading
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* Custom solution - Build our own configuration loader
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## Decision Outcome
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Chosen option: "Viper" because it provides comprehensive configuration management with support for multiple sources, good validation capabilities, type-safe loading, and is widely used in the Go ecosystem.
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## Pros and Cons of the Options
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### Viper
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* Good, because supports multiple configuration sources
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* Good, because good validation capabilities
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* Good, because type-safe configuration loading
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* Good, because widely used and well-documented
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* Good, because supports hot reloading
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* Bad, because slightly heavier than alternatives
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* Bad, because more complex API
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### Koanf
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* Good, because lightweight
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* Good, because good performance
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* Good, because simple API
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* Bad, because less feature-rich than Viper
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* Bad, because smaller community
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### envconfig
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* Good, because very simple
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* Good, because good for environment variables
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* Bad, because limited to environment variables
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* Bad, because no file support
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### Custom solution
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* Good, because tailored to our needs
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* Good, because no external dependencies
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* Bad, because time-consuming to develop
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* Bad, because need to maintain ourselves
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* Bad, because likely less feature-rich
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## Implementation Example
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```go
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// Configuration structure
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type Config struct {
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Server ServerConfig `mapstructure:"server"`
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Shutdown ShutdownConfig `mapstructure:"shutdown"`
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Logging LoggingConfig `mapstructure:"logging"`
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}
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// Loading configuration
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func LoadConfig() (*Config, error) {
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v := viper.New()
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// Set defaults
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v.SetDefault("server.host", "0.0.0.0")
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v.SetDefault("server.port", 8080)
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// Read config file
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v.SetConfigName("config")
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v.SetConfigType("yaml")
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v.AddConfigPath(".")
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if err := v.ReadInConfig(); err != nil {
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if _, ok := err.(viper.ConfigFileNotFoundError); !ok {
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return nil, err
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}
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}
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// Bind environment variables
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v.AutomaticEnv()
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v.SetEnvPrefix("DLC")
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// Unmarshal into struct
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var config Config
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if err := v.Unmarshal(&config); err != nil {
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return nil, err
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}
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return &config, nil
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}
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```
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## Configuration Priority
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The implementation follows this priority order:
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1. **Config file** (highest priority)
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2. **Environment variables** (override defaults)
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3. **Default values** (lowest priority)
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## Links
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* [Viper GitHub](https://github.com/spf13/viper)
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* [Viper Documentation](https://github.com/spf13/viper#readme)
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* [Koanf GitHub](https://github.com/knadh/koanf)
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* [envconfig GitHub](https://github.com/kelseyhightower/envconfig)
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## Configuration File Example
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```yaml
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# config.yaml
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server:
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host: "0.0.0.0"
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port: 8080
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shutdown:
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timeout: 30s
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logging:
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json: false
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level: "trace"
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```
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## Environment Variables
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```bash
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# Set configuration via environment variables
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export DLC_SERVER_HOST="0.0.0.0"
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export DLC_SERVER_PORT=8080
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export DLC_SHUTDOWN_TIMEOUT=30s
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export DLC_LOGGING_JSON=false
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``` |