spf13--viper/README.md

viper

Go configuration with fangs

What is Viper?

Viper is a complete configuration solution. Designed to work within an application to handle file based configuration and seamlessly marry that with command line flags which can also be used to control application behavior. Viper also supports retrieving configuration values from remote key/value stores. Etcd and Consul are supported.

Why Viper?

When building a modern application you don’t want to have to worry about configuration file formats, you want to focus on building awesome software. Viper is here to help with that.

Viper does the following for you:

1. Find, load and marshall a configuration file in YAML, TOML or JSON.
2. Provide a mechanism to setDefault values for your different configuration options
3. Provide a mechanism to setOverride values for options specified through command line flags.
4. Provide an alias system to easily rename parameters without breaking existing code.
5. Make it easy to tell the difference between when a user has provided a command line or config file which is the same as the default.

Viper believes that:

1. command line flags take precedence over options set in config files
2. config files take precedence over options set in remote key/value stores
3. remote key/value stores take precedence over defaults

Viper configuration keys are case insensitive.

Usage

Initialization

viper.SetConfigName("config") // name of config file (without extension)
viper.AddConfigPath("/etc/appname/")   // path to look for the config file in
viper.AddConfigPath("$HOME/.appname")  // call multiple times to add many search paths
viper.ReadInConfig() // Find and read the config file

Setting Defaults

viper.SetDefault("ContentDir", "content")
viper.SetDefault("LayoutDir", "layouts")
viper.SetDefault("Indexes", map[string]string{"tag": "tags", "category": "categories"})

Setting Overrides

viper.Set("Verbose", true)
viper.Set("LogFile", LogFile)

Registering and Using Aliases

viper.RegisterAlias("loud", "Verbose")

viper.Set("verbose", true) // same result as next line
viper.Set("loud", true)   // same result as prior line

viper.GetBool("loud") // true
viper.GetBool("verbose") // true

Getting Values

viper.GetString("logfile") // case insensitive Setting & Getting
if viper.GetBool("verbose") {
    fmt.Println("verbose enabled")
}

Remote Key/Value Store Support

Viper will read a config string (as JSON, TOML, or YAML) retrieved from a path in a Key/Value store such as Etcd or Consul. These values take precedence over default values, but are overriden by configuration values retrieved from disk, flags, or environment variables.

Viper uses crypt to retrieve configuration from the k/v store, which means that you can store your configuration values encrypted and have them automatically decrypted if you have the correct gpg keyring. Encryption is optional.

You can use remote configuration in conjunction with local configuration, or independently of it.

crypt has a command-line helper that you can use to put configurations in your k/v store. crypt defaults to etcd on http://127.0.0.1:4001.

go get github.com/xordataexchange/crypt/bin/crypt
crypt set -plaintext /config/hugo.json /Users/hugo/settings/config.json

Confirm that your value was set:

crypt get -plaintext /config/hugo.json

See the crypt documentation for examples of how to set encrypted values, or how to use Consul.

Remote Key/Value Store Example - Unencrypted

viper.AddRemoteProvider("etcd", "http://127.0.0.1:4001","/config/hugo.json")
viper.SetConfigType("json") // because there is no file extension in a stream of bytes
err := viper.ReadRemoteConfig()

Remote Key/Value Store Example - Encrypted

viper.AddSecureRemoteProvider("etcd","http://127.0.0.1:4001","/config/hugo.json","/etc/secrets/mykeyring.gpg")
viper.SetConfigType("json") // because there is no file extension in a stream of bytes
err := viper.ReadRemoteConfig()

Q & A

Q: Why not INI files?

A: Ini files are pretty awful. There’s no standard format and they are hard to validate. Viper is designed to work with YAML, TOML or JSON files. If someone really wants to add this feature, I’d be happy to merge it. It’s easy to specify which formats your application will permit.

Q: Why is it called "viper"?

A: Viper is designed to be a companion to Cobra. While both can operate completely independently, together they make a powerful pair to handle much of your application foundation needs.

Q: Why is it called "Cobra"?

A: Is there a better name for a commander?