viper

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README

viper Build Status

Go configuration with fangs

What is Viper?

Viper is a complete configuration solution for go applications. It has been designed to work within an application to handle all types of configuration. It supports

  • setting defaults
  • reading from json, toml and yaml config files
  • reading from environment variables
  • reading from remote config systems (Etcd or Consul), watching changes
  • reading from command line flags
  • reading from buffer
  • setting explicit values

It can be thought of as a registry for all of your applications configuration needs.

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 marshal a configuration file in JSON, TOML or YAML.
  2. Provide a mechanism to set default values for your different configuration options.
  3. Provide a mechanism to set override 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 uses the following precedence order. Each item takes precedence over the item below it:

  • explicit call to Set
  • flag
  • env
  • config
  • key/value store
  • default

Viper configuration keys are case insensitive.

Putting Values into Viper

Establishing Defaults

A good configuration system will support default values. A default value is not required for a key, but can establish a default to be used in the event that the key hasn’t be set via config file, environment variable, remote configuration or flag.

Examples:

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

If you want to support a config file, Viper requires a minimal configuration so it knows where to look for the config file. Viper supports json, toml and yaml files. Viper can search multiple paths, but currently a single viper only supports a single config file.

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
err := viper.ReadInConfig() // Find and read the config file
if err != nil { // Handle errors reading the config file
    panic(fmt.Errorf("Fatal error config file: %s \n", err))
}
Reading Config from io.Reader

Viper predefined many configuration sources, such as files, environment variables, flags and remote K/V store. But you are not bound to them. You can also implement your own way to require configuration and feed it to viper.

viper.SetConfigType("yaml") // or viper.SetConfigType("YAML")

// any approach to require this configuration into your program. 
var yamlExample = []byte(`
Hacker: true
name: steve
hobbies:
- skateboarding
- snowboarding
- go
clothing:
  jacket: leather
  trousers: denim
age: 35
eyes : brown
beard: true
`)

viper.ReadConfig(bytes.NewBuffer(yamlExample))

viper.Get("name") // this would be "steve"
Setting Overrides

These could be from a command line flag, or from your own application logic.

viper.Set("Verbose", true)
viper.Set("LogFile", LogFile)
Registering and Using Aliases

Aliases permit a single value to be referenced by multiple keys

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
Working with Environment Variables

Viper has full support for environment variables. This enables 12 factor applications out of the box. There are four methods that exist to aid with working with ENV:

  • AutomaticEnv()
  • BindEnv(string...) : error
  • SetEnvPrefix(string)
  • SetEnvReplacer(string...) *strings.Replacer

When working with ENV variables, it’s important to recognize that Viper treats ENV variables as case sensitive.

Viper provides a mechanism to try to ensure that ENV variables are unique. By using SetEnvPrefix, you can tell Viper to use add a prefix while reading from the environment variables. Both BindEnv and AutomaticEnv will use this prefix.

BindEnv takes one or two parameters. The first parameter is the key name, the second is the name of the environment variable. The name of the environment variable is case sensitive. If the ENV variable name is not provided, then Viper will automatically assume that the key name matches the ENV variable name but the ENV variable is IN ALL CAPS. When you explicitly provide the ENV variable name, it does not automatically add the prefix.

One important thing to recognize when working with ENV variables is that the value will be read each time it is accessed. It does not fix the value when the BindEnv is called.

AutomaticEnv is a powerful helper especially when combined with SetEnvPrefix. When called, Viper will check for an environment variable any time a viper.Get request is made. It will apply the following rules. It will check for a environment variable with a name matching the key uppercased and prefixed with the EnvPrefix if set.

SetEnvReplacer allows you to use a strings.Replacer object to rewrite Env keys to an extent. This is useful if you want to use - or something in your Get() calls, but want your environmental variables to use _ delimiters. An example of using it can be found in viper_test.go.

Env example
SetEnvPrefix("spf") // will be uppercased automatically
BindEnv("id")

os.Setenv("SPF_ID", "13") // typically done outside of the app

id := Get("id") // 13
Working with Flags

Viper has the ability to bind to flags. Specifically, Viper supports Pflags as used in the Cobra library.

Like BindEnv, the value is not set when the binding method is called, but when it is accessed. This means you can bind as early as you want, even in an init() function.

The BindPFlag() method provides this functionality.

Example:

serverCmd.Flags().Int("port", 1138, "Port to run Application server on")
viper.BindPFlag("port", serverCmd.Flags().Lookup("port"))
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()
Watching Changes in Etcd - Unencrypted
// alternatively, you can create a new viper instance.
var runtime_viper = viper.New()

runtime_viper.AddRemoteProvider("etcd", "http://127.0.0.1:4001", "/config/hugo.yml")
runtime_viper.SetConfigType("yaml") // because there is no file extension in a stream of bytes

// read from remote config the first time.
err := runtime_viper.ReadRemoteConfig()

// marshal config
runtime_viper.Marshal(&runtime_conf)

// open a goroutine to wath remote changes forever
go func(){
    for {
        time.Sleep(time.Second * 5) // delay after each request

        // currenlty, only tested with etcd support
        err := runtime_viper.WatchRemoteConfig()
        if err != nil {
            log.Errorf("unable to read remote config: %v", err)
            continue
        }

        // marshal new config into our runtime config struct. you can also use channel 
        // to implement a signal to notify the system of the changes
        runtime_viper.Marshal(&runtime_conf)
    }
}()

Getting Values From Viper

In Viper, there are a few ways to get a value depending on what type of value you want to retrieved. The following functions and methods exist:

  • 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
  • GetDuration(key string) : time.Duration
  • IsSet(key string) : bool

One important thing to recognize is that each Get function will return its zero value if it’s not found. To check if a given key exists, the IsSet() method has been provided.

Example:

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

The accessor methods also accept formatted paths to deeply nested keys. For example, if the following JSON file is loaded:

{
    "host": {
        "address": "localhost",
        "port": 5799
    },
    "datastore": {
        "metric": {
            "host": "127.0.0.1",
            "port": 3099
        },
        "warehouse": {
            "host": "198.0.0.1",
            "port": 2112
        }
    }
}

Viper can access a nested field by passing a . delimited path of keys:

GetString("datastore.metric.host") // (returns "127.0.0.1")

This obeys the precendense rules established above; the search for the root key (in this examole, datastore) will cascade through the remaining configuration registries until found. The search for the subkeys (metric and host), however, will not.

For example, if the metric key was not defined in the configuration loaded from file, but was defined in the defaults, Viper would return the zero value.

On the other hand, if the primary key was not defined, Viper would go through the remaining registries looking for it.

Lastly, if there exists a key that matches the delimited key path, its value will be returned instead. E.g.

{
    "datastore.metric.host": "0.0.0.0",
    "host": {
        "address": "localhost",
        "port": 5799
    },
    "datastore": {
        "metric": {
            "host": "127.0.0.1",
            "port": 3099
        },
        "warehouse": {
            "host": "198.0.0.1",
            "port": 2112
        }
    }
}

GetString("datastore.metric.host") //returns "0.0.0.0"
Marshaling

You also have the option of Marshaling all or a specific value to a struct, map, etc.

There are two methods to do this:

  • Marshal(rawVal interface{}) : error
  • MarshalKey(key string, rawVal interface{}) : error

Example:

type config struct {
	Port int
	Name string
}

var C config

err := Marshal(&C)
if err != nil {
	t.Fatalf("unable to decode into struct, %v", err)
}

Viper or Vipers?

Viper comes ready to use out of the box. There is no configuration or initialization needed to begin using Viper. Since most applications will want to use a single central repository for their configuration, the viper package provides this. It is similar to a singleton.

In all of the examples above, they demonstrate using viper in its singleton style approach.

Working with multiple vipers

You can also create many different vipers for use in your application. Each will have it’s own unique set of configurations and values. Each can read from a different config file, key value store, etc. All of the functions that viper package supports are mirrored as methods on a viper.

Example:

x := viper.New()
y := viper.New()

x.SetDefault("ContentDir", "content")
y.SetDefault("ContentDir", "foobar")

...

When working with multiple vipers, it is up to the user to keep track of the different vipers.

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 JSON, TOML or YAML 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?

Documentation

Index

Constants

This section is empty.

Variables

View Source 
var SupportedExts []string = []string{"json", "toml", "yaml", "yml", "properties", "props", "prop"}

Universally supported extensions.

View Source 
var SupportedRemoteProviders []string = []string{"etcd", "consul"}

Universally supported remote providers.

Functions

func AddConfigPath 

func AddConfigPath(in string)

Add a path for Viper to search for the config file in. Can be called multiple times to define multiple search paths.

func AddRemoteProvider 

func AddRemoteProvider(provider, endpoint, path string) error

AddRemoteProvider adds a remote configuration source. Remote Providers are searched in the order they are added. provider is a string value, "etcd" or "consul" are currently supported. endpoint is the url. etcd requires http://ip:port consul requires ip:port path is the path in the k/v store to retrieve configuration To retrieve a config file called myapp.json from /configs/myapp.json you should set path to /configs and set config name (SetConfigName()) to "myapp"

func AddSecureRemoteProvider 

func AddSecureRemoteProvider(provider, endpoint, path, secretkeyring string) error

AddSecureRemoteProvider adds a remote configuration source. Secure Remote Providers are searched in the order they are added. provider is a string value, "etcd" or "consul" are currently supported. endpoint is the url. etcd requires http://ip:port consul requires ip:port secretkeyring is the filepath to your openpgp secret keyring. e.g. /etc/secrets/myring.gpg path is the path in the k/v store to retrieve configuration To retrieve a config file called myapp.json from /configs/myapp.json you should set path to /configs and set config name (SetConfigName()) to "myapp" Secure Remote Providers are implemented with github.com/xordataexchange/crypt

func AllKeys 

func AllKeys() []string

Return all keys regardless where they are set

func AllSettings 

func AllSettings() map[string]interface{}

Return all settings as a map[string]interface{}

func AutomaticEnv 

func AutomaticEnv()

Have Viper check ENV variables for all keys set in config, default & flags

func BindEnv 

func BindEnv(input ...string) (err error)

Binds a Viper key to a ENV variable ENV variables are case sensitive If only a key is provided, it will use the env key matching the key, uppercased. EnvPrefix will be used when set when env name is not provided.

func BindPFlag 

func BindPFlag(key string, flag *pflag.Flag) (err error)

Bind a specific key to a flag (as used by cobra) Example(where serverCmd is a Cobra instance): 

serverCmd.Flags().Int("port", 1138, "Port to run Application server on")
Viper.BindPFlag("port", serverCmd.Flags().Lookup("port"))

func BindPFlags 

func BindPFlags(flags *pflag.FlagSet) (err error)

Bind a full flag set to the configuration, using each flag's long name as the config key.

func ConfigFileUsed 

func ConfigFileUsed() string

Return the file used to populate the config registry

func Debug 

func Debug()

Prints all configuration registries for debugging purposes.

func Get 

func Get(key string) interface{}

Viper is essentially repository for configurations Get can retrieve any value given the key to use Get has the behavior of returning the value associated with the first place from where it is set. Viper will check in the following order: override, flag, env, config file, key/value store, default

Get returns an interface. For a specific value use one of the Get____ methods.

func GetBool 

func GetBool(key string) bool

Returns the value associated with the key asa boolean

func GetDuration 

func GetDuration(key string) time.Duration

Returns the value associated with the key as a duration

func GetFloat64 

func GetFloat64(key string) float64

Returns the value associated with the key as a float64

func GetInt 

func GetInt(key string) int

Returns the value associated with the key as an integer

func GetSizeInBytes 

func GetSizeInBytes(key string) uint

Returns the size of the value associated with the given key in bytes.

func GetString 

func GetString(key string) string

Returns the value associated with the key as a string

func GetStringMap 

func GetStringMap(key string) map[string]interface{}

Returns the value associated with the key as a map of interfaces

func GetStringMapString 

func GetStringMapString(key string) map[string]string

Returns the value associated with the key as a map of strings

func GetStringSlice 

func GetStringSlice(key string) []string

Returns the value associated with the key as a slice of strings

func GetTime 

func GetTime(key string) time.Time

Returns the value associated with the key as time

func InConfig 

func InConfig(key string) bool

Check to see if the given key (or an alias) is in the config file

func IsSet 

func IsSet(key string) bool

Check to see if the key has been set in any of the data locations

func Marshal 

func Marshal(rawVal interface{}) error

Marshals the config into a Struct. Make sure that the tags on the fields of the structure are properly set.

func MarshalKey 

func MarshalKey(key string, rawVal interface{}) error

Takes a single key and marshals it into a Struct

func ReadConfig 

func ReadConfig(in io.Reader) error

func ReadInConfig 

func ReadInConfig() error

Viper will discover and load the configuration file from disk and key/value stores, searching in one of the defined paths.

func ReadRemoteConfig 

func ReadRemoteConfig() error

Attempts to get configuration from a remote source and read it in the remote configuration registry.

func RegisterAlias 

func RegisterAlias(alias string, key string)

Aliases provide another accessor for the same key. This enables one to change a name without breaking the application

func Reset 

func Reset()

Intended for testing, will reset all to default settings. In the public interface for the viper package so applications can use it in their testing as well.

func Set 

func Set(key string, value interface{})

Sets the value for the key in the override regiser. Will be used instead of values obtained via flags, config file, ENV, default, or key/value store

func SetConfigFile 

func SetConfigFile(in string)

Explicitly define the path, name and extension of the config file Viper will use this and not check any of the config paths

func SetConfigName 

func SetConfigName(in string)

Name for the config file. Does not include extension.

func SetConfigType 

func SetConfigType(in string)

Sets the type of the configuration returned by the remote source, e.g. "json".

func SetDefault 

func SetDefault(key string, value interface{})

Set the default value for this key. Default only used when no value is provided by the user via flag, config or ENV.

func SetEnvKeyReplacer 

func SetEnvKeyReplacer(r *strings.Replacer)

SetEnvKeyReplacer sets the strings.Replacer on the viper object Useful for mapping an environmental variable to a key that does not match it.

func SetEnvPrefix 

func SetEnvPrefix(in string)

Define a prefix that ENVIRONMENT variables will use. E.g. if your prefix is "spf", the env registry will look for env. variables that start with "SPF_"

func WatchRemoteConfig 

func WatchRemoteConfig() error

Types

type RemoteConfigError 

type RemoteConfigError string

Denotes encountering an error while trying to pull the configuration from the remote provider.

func (RemoteConfigError) Error 

func (rce RemoteConfigError) Error() string

Returns the formatted remote provider error

type UnsupportedConfigError 

type UnsupportedConfigError string

Denotes encountering an unsupported configuration filetype.

func (UnsupportedConfigError) Error 

func (str UnsupportedConfigError) Error() string

Returns the formatted configuration error.

type UnsupportedRemoteProviderError 

type UnsupportedRemoteProviderError string

Denotes encountering an unsupported remote provider. Currently only Etcd and Consul are supported.

func (UnsupportedRemoteProviderError) Error 

func (str UnsupportedRemoteProviderError) Error() string

Returns the formatted remote provider error.

type Viper 

type Viper struct {
	// contains filtered or unexported fields
}

Viper is a prioritized configuration registry. It maintains a set of configuration sources, fetches values to populate those, and provides them according to the source's priority. The priority of the sources is the following: 1. overrides 2. flags 3. env. variables 4. config file 5. key/value store 6. defaults

For example, if values from the following sources were loaded: 

 Defaults : {
 	"secret": "",
 	"user": "default",
	    "endpoint": "https://localhost"
 }
 Config : {
 	"user": "root"
	    "secret": "defaultsecret"
 }
 Env : {
 	"secret": "somesecretkey"
 }

The resulting config will have the following values: 

{
	"secret": "somesecretkey",
	"user": "root",
	"endpoint": "https://localhost"
}

func New 

func New() *Viper

Returns an initialized Viper instance.

func (*Viper) AddConfigPath 

func (v *Viper) AddConfigPath(in string)

func (*Viper) AddRemoteProvider 

func (v *Viper) AddRemoteProvider(provider, endpoint, path string) error

func (*Viper) AddSecureRemoteProvider 

func (v *Viper) AddSecureRemoteProvider(provider, endpoint, path, secretkeyring string) error

func (*Viper) AllKeys 

func (v *Viper) AllKeys() []string

func (*Viper) AllSettings 

func (v *Viper) AllSettings() map[string]interface{}

func (*Viper) AutomaticEnv 

func (v *Viper) AutomaticEnv()

func (*Viper) BindEnv 

func (v *Viper) BindEnv(input ...string) (err error)

func (*Viper) BindPFlag 

func (v *Viper) BindPFlag(key string, flag *pflag.Flag) (err error)

func (*Viper) BindPFlags 

func (v *Viper) BindPFlags(flags *pflag.FlagSet) (err error)

func (*Viper) ConfigFileUsed 

func (v *Viper) ConfigFileUsed() string

func (*Viper) Debug 

func (v *Viper) Debug()

func (*Viper) Get 

func (v *Viper) Get(key string) interface{}

func (*Viper) GetBool 

func (v *Viper) GetBool(key string) bool

func (*Viper) GetDuration 

func (v *Viper) GetDuration(key string) time.Duration

func (*Viper) GetFloat64 

func (v *Viper) GetFloat64(key string) float64

func (*Viper) GetInt 

func (v *Viper) GetInt(key string) int

func (*Viper) GetSizeInBytes 

func (v *Viper) GetSizeInBytes(key string) uint

func (*Viper) GetString 

func (v *Viper) GetString(key string) string

func (*Viper) GetStringMap 

func (v *Viper) GetStringMap(key string) map[string]interface{}

func (*Viper) GetStringMapString 

func (v *Viper) GetStringMapString(key string) map[string]string

func (*Viper) GetStringSlice 

func (v *Viper) GetStringSlice(key string) []string

func (*Viper) GetTime 

func (v *Viper) GetTime(key string) time.Time

func (*Viper) InConfig 

func (v *Viper) InConfig(key string) bool

func (*Viper) IsSet 

func (v *Viper) IsSet(key string) bool

func (*Viper) Marshal 

func (v *Viper) Marshal(rawVal interface{}) error

func (*Viper) MarshalKey 

func (v *Viper) MarshalKey(key string, rawVal interface{}) error

func (*Viper) ReadConfig 

func (v *Viper) ReadConfig(in io.Reader) error

func (*Viper) ReadInConfig 

func (v *Viper) ReadInConfig() error

func (*Viper) ReadRemoteConfig 

func (v *Viper) ReadRemoteConfig() error

func (*Viper) RegisterAlias 

func (v *Viper) RegisterAlias(alias string, key string)

func (*Viper) Set 

func (v *Viper) Set(key string, value interface{})

func (*Viper) SetConfigFile 

func (v *Viper) SetConfigFile(in string)

func (*Viper) SetConfigName 

func (v *Viper) SetConfigName(in string)

func (*Viper) SetConfigType 

func (v *Viper) SetConfigType(in string)

func (*Viper) SetDefault 

func (v *Viper) SetDefault(key string, value interface{})

func (*Viper) SetEnvKeyReplacer 

func (v *Viper) SetEnvKeyReplacer(r *strings.Replacer)

func (*Viper) SetEnvPrefix 

func (v *Viper) SetEnvPrefix(in string)

func (*Viper) WatchRemoteConfig 

func (v *Viper) WatchRemoteConfig() error

Source Files

View all Source files

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