Confer

A viper-derived configuration management package.

Significant changes include:

• Materialized path access of configuration variables.
• The singleton has been replaced by separate instances, largely for testability.
• The ability to load and merge multiple configuration files.

Features

1. Merging multiple configuration sources.

  config.ReadPaths("application.yaml", "environments/production.yaml")`

2. Materialized path access of nested configuration data.

  config.GetInt('app.database.port')

3. Binding of environment variables to configuration data.

   APP_DATABASE_PORT=3456 go run app.go

4. User-defined helper methods.

Usage

Initialization

Create your configuration instance:

config := confer.NewConfig()

Then set defaults, read paths, set overrides:

config.SetDefault("environment", "development")
config.ReadPaths("application.yaml", "environments/production.yml")
config.Set("environment", "development")

No worries! Confer will conveniently merge deeply nested structures for you. My usual configuration setup looks like this:

config
  ├── application.development.yml
  ├── application.production.yml
  └── application.yml

For example, an application-specific config package like the one below can be used to drive a core configuration with environment specific overrides:

var App *confer.Config

func init() {
  App = confer.NewConfig()
  appenv := os.Getenv("MYAPP_ENV");
  paths := []string{"application.yml"}

  if (appenv != "") {
    paths = append(paths, fmt.Sprintf("application.%s.yml", appenv))
  }

  if err := App.ReadPaths(paths...); err != nil {
    log.Warn(err)
  }
}

Setting Defaults

Sets a value if it hasn't already been set. Multiple invocations won't clobber existing values, so you'll likely want to do this before reading from files.

config := confer.NewConfig()
config.ReadPaths("application.yaml")
config.SetDefault("ContentDir", "content")
config.SetDefault("LayoutDir", "layouts")
config.SetDefault("Indexes", map[string]string{"tag": "tags", "category": "categories"})

Setting Keys / Value Pairs

Sets a value. Has lower precedence than environment variables or command line flags.

config.Set("verbose", true)
config.Set("logfile", "/var/log/config.log")

Getting Values

There are a variety of accessors for accessing type-coerced values:

Get(key string) : interface{}
GetBool(key string) : bool
GetFloat64(key string) : float64
GetInt(key string) : int
GetString(key string) : string
GetStringMap(key string) : map[string]interface{}
GetStringMapString(key string) : map[string]string
GetStringSlice(key string) : []string
GetTime(key string) : time.Time
IsSet(key string) : bool

Deep Configuration Data

Materialized paths allow easy access of deeply nested config data:

logger_config := config.GetStringMap("logger.stdout")

Because periods aren't valid environment variable characters, when using automatic environment bindings (see below), substitute with underscores:

LOGGER_STDOUT=/var/log/myapp go run server.go

Environment Bindings

Automatic Binding

Confer can automatically bind all existing configuration keys to environment variables.

Given some sort of application.yaml

---
app:
   log: "verbose"
   database:
       host: "localhost"

And this pair of calls:

config.ReadPaths("application.yaml")
config.AutomaticEnv()

You'll have the following environment variables exposed for configuration:

APP_LOG
APP_DATABASE_HOST

Selective Binding

If this automatic binding is bizarre, you can selectively bind environment variables with ``BindEnv()`.

config.BindEnv("APP_LOG", "app.log")

Helpers

You can Set a func() interface{} at a configuration key to provide values dynamically:

config.Set("dbstring", func() interface {} {
  return fmt.Sprintf(
    "user=%s dbname=%s sslmode=%s",
    config.GetString("database.user"),
    config.GetString("database.name"),
    config.GetString("database.sslmode"),
  )
})
assert(config.GetString("dbstring") ==  "user=doug dbname=pruden sslmode=pushups")