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@ -7,41 +7,41 @@ Go configuration with fangs
## What is Viper? ## What is Viper?
Viper is a complete configuration solution for go applications. It has Viper is a complete configuration solution for go applications. It is designed
been designed to work within an application to handle all types of to work within an application, and can handle all types of configuration needs
configuration. It supports and formats. It supports:
* setting defaults * setting defaults
* reading from json, toml and yaml config files * reading from JSON, TOML, and YAML config files
* reading from environment variables * reading from environment variables
* reading from remote config systems (Etcd or Consul), watching changes * reading from remote config systems (Etcd or Consul), and watching changes
* reading from command line flags * reading from command line flags
* reading from buffer * reading from buffer
* setting explicit values * setting explicit values
It can be thought of as a registry for all of your applications Viper can be thought of as a registry for all of your applications
configuration needs. configuration needs.
## Why Viper? ## Why Viper?
When building a modern application, you don’t want to have to worry about When building a modern application, you don’t want to worry about
configuration file formats; you want to focus on building awesome software. configuration file formats; you want to focus on building awesome software.
Viper is here to help with that. Viper is here to help with that.
Viper does the following for you: Viper does the following for you:
1. Find, load and marshal a configuration file in JSON, TOML or YAML. 1. Find, load, and marshal a configuration file in JSON, TOML, or YAML.
2. Provide a mechanism to set default values for your different 2. Provide a mechanism to set default values for your different
configuration options. configuration options.
3. Provide a mechanism to set override values for options specified 3. Provide a mechanism to set override values for options specified through
through command line flags. command line flags.
4. Provide an alias system to easily rename parameters without breaking 4. Provide an alias system to easily rename parameters without breaking existing
existing code. code.
5. Make it easy to tell the difference between when a user has provided 5. Make it easy to tell the difference between when a user has provided a
a command line or config file which is the same as the default. command line or config file which is the same as the default.
Viper uses the following precedence order. Each item takes precedence Viper uses the following precedence order. Each item takes precedence over the
over the item below it: item below it:
* explicit call to Set * explicit call to Set
* flag * flag
@ -56,10 +56,9 @@ Viper configuration keys are case insensitive.
### Establishing Defaults ### Establishing Defaults
A good configuration system will support default values. A default value A good configuration system will support default values. A default value is not
is not required for a key, but can establish a default to be used in the required for a key, but it's useful in the event that a key hasn’t be set via
event that the key hasn’t be set via config file, environment variable, config file, environment variable, remote configuration or flag.
remote configuration or flag.
Examples: Examples:
@ -71,10 +70,9 @@ viper.SetDefault("Taxonomies", map[string]string{"tag": "tags", "category": "cat
### Reading Config Files ### Reading Config Files
If you want to support a config file, Viper requires a minimal Viper requires minimal configuration so it knows where to look for config files.
configuration so it knows where to look for the config file. Viper Viper supports JSON, TOML and YAML files. Viper can search multiple paths, but
supports json, toml and yaml files. Viper can search multiple paths, but currently a single Viper instance only supports a single configuration file.
currently a single viper only supports a single config file.
```go ```go
viper.SetConfigName("config") // name of config file (without extension) viper.SetConfigName("config") // name of config file (without extension)
@ -88,14 +86,14 @@ if err != nil { // Handle errors reading the config file
### Reading Config from io.Reader ### Reading Config from io.Reader
Viper predefined many configuration sources, such as files, environment variables, flags and Viper predefines many configuration sources such as files, environment
remote K/V store. But you are not bound to them. You can also implement your own way to variables, flags, and remote K/V store, but you are not bound to them. You can
require configuration and feed it to viper. also implement your own required configuration source and feed it to viper.
```go ```go
viper.SetConfigType("yaml") // or viper.SetConfigType("YAML") viper.SetConfigType("yaml") // or viper.SetConfigType("YAML")
// any approach to require this configuration into your program. // any approach to require this configuration into your program.
var yamlExample = []byte(` var yamlExample = []byte(`
Hacker: true Hacker: true
name: steve name: steve
@ -142,44 +140,43 @@ viper.GetBool("verbose") // true
### Working with Environment Variables ### Working with Environment Variables
Viper has full support for environment variables. This enables 12 factor Viper has full support for environment variables. This enables 12 factor
applications out of the box. There are four methods that exist to aid applications out of the box. There are four methods that exist to aid working
with working with ENV: with ENV:
* AutomaticEnv() * `AutomaticEnv()`
* BindEnv(string...) : error * `BindEnv(string...) : error`
* SetEnvPrefix(string) * `SetEnvPrefix(string)`
* SetEnvReplacer(string...) *strings.Replacer * `SetEnvReplacer(string...) *strings.Replacer`
_When working with ENV variables, it’s important to recognize that Viper _When working with ENV variables, it’s important to recognize that Viper
treats ENV variables as case sensitive._ treats ENV variables as case sensitive._
Viper provides a mechanism to try to ensure that ENV variables are Viper provides a mechanism to try to ensure that ENV variables are unique. By
unique. By using SetEnvPrefix, you can tell Viper to use add a prefix using `SetEnvPrefix`, you can tell Viper to use add a prefix while reading from
while reading from the environment variables. Both BindEnv and the environment variables. Both `BindEnv` and `AutomaticEnv` will use this
AutomaticEnv will use this prefix. prefix.
BindEnv takes one or two parameters. The first parameter is the key `BindEnv` takes one or two parameters. The first parameter is the key name, the
name, the second is the name of the environment variable. The name of second is the name of the environment variable. The name of the environment
the environment variable is case sensitive. If the ENV variable name is variable is case sensitive. If the ENV variable name is not provided, then
not provided, then Viper will automatically assume that the key name Viper will automatically assume that the key name matches the ENV variable name,
matches the ENV variable name but the ENV variable is IN ALL CAPS. When but the ENV variable is IN ALL CAPS. When you explicitly provide the ENV
you explicitly provide the ENV variable name, it **does not** variable name, it **does not** automatically add the prefix.
automatically add the prefix.
One important thing to recognize when working with ENV variables is that One important thing to recognize when working with ENV variables is that the
the value will be read each time it is accessed. It does not fix the value will be read each time it is accessed. Viper does not fix the value when
value when the BindEnv is called. the `BindEnv` is called.
AutomaticEnv is a powerful helper especially when combined with `AutomaticEnv` is a powerful helper especially when combined with
SetEnvPrefix. When called, Viper will check for an environment variable `SetEnvPrefix`. When called, Viper will check for an environment variable any
any time a viper.Get request is made. It will apply the following rules. time a `viper.Get` request is made. It will apply the following rules. It will
It will check for a environment variable with a name matching the key check for a environment variable with a name matching the key uppercased and
uppercased and prefixed with the EnvPrefix if set. prefixed with the `EnvPrefix` if set.
SetEnvReplacer allows you to use a `strings.Replacer` object to rewrite Env keys `SetEnvReplacer` allows you to use a `strings.Replacer` object to rewrite Env
to an extent. This is useful if you want to use `-` or something in your Get() keys to an extent. This is useful if you want to use `-` or something in your
calls, but want your environmental variables to use `_` delimiters. An example `Get()` calls, but want your environmental variables to use `_` delimiters. An
of using it can be found in `viper_test.go`. example of using it can be found in `viper_test.go`.
#### Env example #### Env example
@ -194,14 +191,14 @@ id := Get("id") // 13
### Working with Flags ### Working with Flags
Viper has the ability to bind to flags. Specifically, Viper supports Viper has the ability to bind to flags. Specifically, Viper supports `Pflags`
Pflags as used in the [Cobra](https://github.com/spf13/cobra) library. as used in the [Cobra](https://github.com/spf13/cobra) library.
Like BindEnv, the value is not set when the binding method is called, but Like `BindEnv`, the value is not set when the binding method is called, but when
when it is accessed. This means you can bind as early as you want, even it is accessed. This means you can bind as early as you want, even in an
in an init() function. `init()` function.
The BindPFlag() method provides this functionality. The `BindPFlag()` method provides this functionality.
Example: Example:
@ -212,25 +209,26 @@ viper.BindPFlag("port", serverCmd.Flags().Lookup("port"))
### Remote Key/Value Store Support ### Remote Key/Value Store Support
To enable remote support in Viper, do a blank import of the `viper/remote` package: To enable remote support in Viper, do a blank import of the `viper/remote`
package:
`import _ github.com/spf13/viper/remote` `import _ github.com/spf13/viper/remote`
Viper will read a config string (as JSON, TOML, or YAML) retrieved from a Viper will read a config string (as JSON, TOML, or YAML) retrieved from a path
path in a Key/Value store such as Etcd or Consul. These values take precedence in a Key/Value store such as Etcd or Consul. These values take precedence over
over default values, but are overriden by configuration values retrieved from disk, default values, but are overridden by configuration values retrieved from disk,
flags, or environment variables. flags, or environment variables.
Viper uses [crypt](https://github.com/xordataexchange/crypt) to retrieve configuration Viper uses [crypt](https://github.com/xordataexchange/crypt) to retrieve
from the K/V store, which means that you can store your configuration values configuration from the K/V store, which means that you can store your
encrypted and have them automatically decrypted if you have the correct configuration values encrypted and have them automatically decrypted if you have
gpg keyring. Encryption is optional. the correct gpg keyring. Encryption is optional.
You can use remote configuration in conjunction with local configuration, or You can use remote configuration in conjunction with local configuration, or
independently of it. independently of it.
`crypt` has a command-line helper that you can use to put configurations `crypt` has a command-line helper that you can use to put configurations in your
in your K/V store. `crypt` defaults to etcd on http://127.0.0.1:4001. K/V store. `crypt` defaults to etcd on http://127.0.0.1:4001.
```bash ```bash
$ go get github.com/xordataexchange/crypt/bin/crypt $ go get github.com/xordataexchange/crypt/bin/crypt
@ -243,8 +241,8 @@ Confirm that your value was set:
$ crypt get -plaintext /config/hugo.json $ crypt get -plaintext /config/hugo.json
``` ```
See the `crypt` documentation for examples of how to set encrypted values, or how See the `crypt` documentation for examples of how to set encrypted values, or
to use Consul. how to use Consul.
### Remote Key/Value Store Example - Unencrypted ### Remote Key/Value Store Example - Unencrypted
@ -298,24 +296,24 @@ go func(){
## Getting Values From Viper ## 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. In Viper, there are a few ways to get a value depending on the value's type.
The following functions and methods exist: The following functions and methods exist:
* Get(key string) : interface{} * `Get(key string) : interface{}`
* GetBool(key string) : bool * `GetBool(key string) : bool`
* GetFloat64(key string) : float64 * `GetFloat64(key string) : float64`
* GetInt(key string) : int * `GetInt(key string) : int`
* GetString(key string) : string * `GetString(key string) : string`
* GetStringMap(key string) : map[string]interface{} * `GetStringMap(key string) : map[string]interface{}`
* GetStringMapString(key string) : map[string]string * `GetStringMapString(key string) : map[string]string`
* GetStringSlice(key string) : []string * `GetStringSlice(key string) : []string`
* GetTime(key string) : time.Time * `GetTime(key string) : time.Time`
* GetDuration(key string) : time.Duration * `GetDuration(key string) : time.Duration`
* IsSet(key string) : bool * `IsSet(key string) : bool`
One important thing to recognize is that each Get function will return One important thing to recognize is that each Get function will return a zero
its zero value if it’s not found. To check if a given key exists, the IsSet() value if it’s not found. To check if a given key exists, the `IsSet()` method
method has been provided. has been provided.
Example: Example:
```go ```go
@ -326,8 +324,8 @@ if viper.GetBool("verbose") {
``` ```
### Accessing nested keys ### Accessing nested keys
The accessor methods also accept formatted paths to deeply nested keys. The accessor methods also accept formatted paths to deeply nested keys. For
For example, if the following JSON file is loaded: example, if the following JSON file is loaded:
```json ```json
{ {
@ -355,18 +353,19 @@ Viper can access a nested field by passing a `.` delimited path of keys:
GetString("datastore.metric.host") // (returns "127.0.0.1") GetString("datastore.metric.host") // (returns "127.0.0.1")
``` ```
This obeys the precendense rules established above; the search for the root key This obeys the precedence rules established above; the search for the root key
(in this examole, `datastore`) will cascade through the remaining configuration registries (in this example, `datastore`) will cascade through the remaining configuration
until found. The search for the subkeys (`metric` and `host`), however, will not. registries until found. The search for the sub-keys (`metric` and `host`),
however, will not.
For example, if the `metric` key was not defined in the configuration loaded 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. 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 On the other hand, if the primary key was not defined, Viper would go through
remaining registries looking for it. the remaining registries looking for it.
Lastly, if there exists a key that matches the delimited key path, its value will Lastly, if there exists a key that matches the delimited key path, its value
be returned instead. E.g. will be returned instead. E.g.
```json ```json
{ {
@ -392,12 +391,13 @@ GetString("datastore.metric.host") //returns "0.0.0.0"
### Marshaling ### Marshaling
You also have the option of Marshaling all or a specific value to a struct, map, etc. You also have the option of Marshaling all or a specific value to a struct, map,
etc.
There are two methods to do this: There are two methods to do this:
* Marshal(rawVal interface{}) : error * `Marshal(rawVal interface{}) : error`
* MarshalKey(key string, rawVal interface{}) : error * `MarshalKey(key string, rawVal interface{}) : error`
Example: Example:
@ -418,19 +418,19 @@ if err != nil {
## Viper or Vipers? ## Viper or Vipers?
Viper comes ready to use out of the box. There is no configuration or Viper comes ready to use out of the box. There is no configuration or
initialization needed to begin using Viper. Since most applications will initialization needed to begin using Viper. Since most applications will want
want to use a single central repository for their configuration, the to use a single central repository for their configuration, the viper package
viper package provides this. It is similar to a singleton. provides this. It is similar to a singleton.
In all of the examples above, they demonstrate using viper in its In all of the examples above, they demonstrate using viper in it's singleton
singleton style approach. style approach.
### Working with multiple vipers ### Working with multiple vipers
You can also create many different vipers for use in your application. You can also create many different vipers for use in your application. Each will
Each will have it’s own unique set of configurations and values. Each have it’s own unique set of configurations and values. Each can read from a
can read from a different config file, key value store, etc. All of the different config file, key value store, etc. All of the functions that viper
functions that viper package supports are mirrored as methods on a viper. package supports are mirrored as methods on a viper.
Example: Example:
@ -444,8 +444,8 @@ y.SetDefault("ContentDir", "foobar")
//... //...
``` ```
When working with multiple vipers, it is up to the user to keep track of When working with multiple vipers, it is up to the user to keep track of the
the different vipers. different vipers.
## Q & A ## Q & A
@ -453,13 +453,13 @@ Q: Why not INI files?
A: Ini files are pretty awful. There’s no standard format, and they are hard to 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 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 really wants to add this feature, I’d be happy to merge it. It’s easy to specify
specify which formats your application will permit. which formats your application will permit.
Q: Why is it called “Viper”? Q: Why is it called “Viper”?
A: Viper is designed to be a [companion](http://en.wikipedia.org/wiki/Viper_(G.I._Joe)) to A: Viper is designed to be a [companion](http://en.wikipedia.org/wiki/Viper_(G.I._Joe))
[Cobra](https://github.com/spf13/cobra). While both can operate completely to [Cobra](https://github.com/spf13/cobra). While both can operate completely
independently, together they make a powerful pair to handle much of your independently, together they make a powerful pair to handle much of your
application foundation needs. application foundation needs.