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@ -7,41 +7,41 @@ 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
Viper is a complete configuration solution for go applications. It is designed
to work within an application, and can handle all types of configuration needs
and formats. It supports:
* setting defaults
* reading from json, toml and yaml config files
* reading from JSON, TOML, and YAML config files
* 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 buffer
* 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.
## 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.
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.
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.
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:
Viper uses the following precedence order. Each item takes precedence over the
item below it:
* explicit call to Set
* flag
@ -56,10 +56,9 @@ Viper configuration keys are case insensitive.
### 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.
A good configuration system will support default values. A default value is not
required for a key, but it's useful in the event that a key hasn’t be set via
config file, environment variable, remote configuration or flag.
Examples:
@ -71,10 +70,9 @@ viper.SetDefault("Taxonomies", map[string]string{"tag": "tags", "category": "cat
### 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 requires minimal configuration so it knows where to look for config files.
Viper supports JSON, TOML and YAML files. Viper can search multiple paths, but
currently a single Viper instance only supports a single configuration file.
```go
viper.SetConfigName("config") // name of config file (without extension)
@ -88,9 +86,9 @@ if err != nil { // Handle errors reading the config file
### 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 predefines 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 required configuration source and feed it to viper.
```go
viper.SetConfigType("yaml") // or viper.SetConfigType("YAML")
@ -142,44 +140,43 @@ 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:
applications out of the box. There are four methods that exist to aid working
with ENV:
* AutomaticEnv()
* BindEnv(string...) : error
* SetEnvPrefix(string)
* SetEnvReplacer(string...) *strings.Replacer
* `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.
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.
`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.
One important thing to recognize when working with ENV variables is that the
value will be read each time it is accessed. Viper 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.
`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`.
`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
@ -194,14 +191,14 @@ id := Get("id") // 13
### Working with Flags
Viper has the ability to bind to flags. Specifically, Viper supports
Pflags as used in the [Cobra](https://github.com/spf13/cobra) library.
Viper has the ability to bind to flags. Specifically, Viper supports `Pflags`
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
when it is accessed. This means you can bind as early as you want, even
in an init() function.
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.
The `BindPFlag()` method provides this functionality.
Example:
@ -212,25 +209,26 @@ viper.BindPFlag("port", serverCmd.Flags().Lookup("port"))
### 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`
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,
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 overridden by configuration values retrieved from disk,
flags, or environment variables.
Viper uses [crypt](https://github.com/xordataexchange/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.
Viper uses [crypt](https://github.com/xordataexchange/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.
`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.
```bash
$ go get github.com/xordataexchange/crypt/bin/crypt
@ -243,8 +241,8 @@ 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.
See the `crypt` documentation for examples of how to set encrypted values, or
how to use Consul.
### Remote Key/Value Store Example - Unencrypted
@ -298,24 +296,24 @@ go func(){
## 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:
* 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
* `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.
One important thing to recognize is that each Get function will return a zero
value if it’s not found. To check if a given key exists, the `IsSet()` method
has been provided.
Example:
```go
@ -326,8 +324,8 @@ if viper.GetBool("verbose") {
```
### Accessing nested keys
The accessor methods also accept formatted paths to deeply nested keys.
For example, if the following JSON file is loaded:
The accessor methods also accept formatted paths to deeply nested keys. For
example, if the following JSON file is loaded:
```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")
```
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.
This obeys the precedence rules established above; the search for the root key
(in this example, `datastore`) will cascade through the remaining configuration
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
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.
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.
Lastly, if there exists a key that matches the delimited key path, its value
will be returned instead. E.g.
```json
{
@ -392,12 +391,13 @@ 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.
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
* `Marshal(rawVal interface{}) : error`
* `MarshalKey(key string, rawVal interface{}) : error`
Example:
@ -418,19 +418,19 @@ if err != nil {
## 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.
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.
In all of the examples above, they demonstrate using viper in it's 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.
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:
@ -444,8 +444,8 @@ y.SetDefault("ContentDir", "foobar")
//...
```
When working with multiple vipers, it is up to the user to keep track of
the different vipers.
When working with multiple vipers, it is up to the user to keep track of the
different vipers.
## 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
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.
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](http://en.wikipedia.org/wiki/Viper_(G.I._Joe)) to
[Cobra](https://github.com/spf13/cobra). While both can operate completely
A: Viper is designed to be a [companion](http://en.wikipedia.org/wiki/Viper_(G.I._Joe))
to [Cobra](https://github.com/spf13/cobra). While both can operate completely
independently, together they make a powerful pair to handle much of your
application foundation needs.