viper

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 Go to latest Published: Dec 18, 2023 License: MIT Imports: 30 Imported by: 83,838

README

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Viper

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Go configuration with fangs!

Many Go projects are built using Viper including:

Install

go get github.com/spf13/viper

Note: Viper uses Go Modules to manage dependencies.

What is Viper?

Viper is a complete configuration solution for Go applications including 12-Factor apps. 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, YAML, HCL, envfile and Java properties config files
  • live watching and re-reading of config files (optional)
  • reading from environment variables
  • reading from remote config systems (etcd or Consul), and watching changes
  • reading from command line flags
  • reading from buffer
  • setting explicit values

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 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 unmarshal a configuration file in JSON, TOML, YAML, HCL, INI, envfile or Java properties formats.
  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

Important: Viper configuration keys are case insensitive. There are ongoing discussions about making that optional.

Putting Values into Viper

Establishing Defaults

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 been 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

Viper requires minimal configuration so it knows where to look for config files. Viper supports JSON, TOML, YAML, HCL, INI, envfile and Java Properties files. Viper can search multiple paths, but currently a single Viper instance only supports a single configuration file. Viper does not default to any configuration search paths leaving defaults decision to an application.

Here is an example of how to use Viper to search for and read a configuration file. None of the specific paths are required, but at least one path should be provided where a configuration file is expected.

viper.SetConfigName("config") // name of config file (without extension)
viper.SetConfigType("yaml") // REQUIRED if the config file does not have the extension in the name
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.AddConfigPath(".")               // optionally look for config in the working directory
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: %w", err))
}

You can handle the specific case where no config file is found like this:

if err := viper.ReadInConfig(); err != nil {
	if _, ok := err.(viper.ConfigFileNotFoundError); ok {
		// Config file not found; ignore error if desired
	} else {
		// Config file was found but another error was produced
	}
}

// Config file found and successfully parsed

NOTE [since 1.6]: You can also have a file without an extension and specify the format programmatically. For those configuration files that lie in the home of the user without any extension like .bashrc

Writing Config Files

Reading from config files is useful, but at times you want to store all modifications made at run time. For that, a bunch of commands are available, each with its own purpose:

  • WriteConfig - writes the current viper configuration to the predefined path, if exists. Errors if no predefined path. Will overwrite the current config file, if it exists.
  • SafeWriteConfig - writes the current viper configuration to the predefined path. Errors if no predefined path. Will not overwrite the current config file, if it exists.
  • WriteConfigAs - writes the current viper configuration to the given filepath. Will overwrite the given file, if it exists.
  • SafeWriteConfigAs - writes the current viper configuration to the given filepath. Will not overwrite the given file, if it exists.

As a rule of the thumb, everything marked with safe won't overwrite any file, but just create if not existent, whilst the default behavior is to create or truncate.

A small examples section:

viper.WriteConfig() // writes current config to predefined path set by 'viper.AddConfigPath()' and 'viper.SetConfigName'
viper.SafeWriteConfig()
viper.WriteConfigAs("/path/to/my/.config")
viper.SafeWriteConfigAs("/path/to/my/.config") // will error since it has already been written
viper.SafeWriteConfigAs("/path/to/my/.other_config")

Watching and re-reading config files

Viper supports the ability to have your application live read a config file while running.

Gone are the days of needing to restart a server to have a config take effect, viper powered applications can read an update to a config file while running and not miss a beat.

Simply tell the viper instance to watchConfig. Optionally you can provide a function for Viper to run each time a change occurs.

Make sure you add all of the configPaths prior to calling WatchConfig()

viper.OnConfigChange(func(e fsnotify.Event) {
	fmt.Println("Config file changed:", e.Name)
})
viper.WatchConfig()

Reading Config from io.Reader

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.

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)
viper.Set("host.port", 5899)   // set subset

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 five methods that exist to aid working with ENV:

  • AutomaticEnv()
  • BindEnv(string...) : error
  • SetEnvPrefix(string)
  • SetEnvKeyReplacer(string...) *strings.Replacer
  • AllowEmptyEnv(bool)

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 a prefix while reading from the environment variables. Both BindEnv and AutomaticEnv will use this prefix.

BindEnv takes one or more parameters. The first parameter is the key name, the rest are the name of the environment variables to bind to this key. If more than one are provided, they will take precedence in the specified order. The name of the environment variable is case sensitive. If the ENV variable name is not provided, then Viper will automatically assume that the ENV variable matches the following format: prefix + "_" + the key name in ALL CAPS. When you explicitly provide the ENV variable name (the second parameter), it does not automatically add the prefix. For example if the second parameter is "id", Viper will look for the ENV variable "ID".

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 an environment variable with a name matching the key uppercased and prefixed with the EnvPrefix if set.

SetEnvKeyReplacer 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.

Alternatively, you can use EnvKeyReplacer with NewWithOptions factory function. Unlike SetEnvKeyReplacer, it accepts a StringReplacer interface allowing you to write custom string replacing logic.

By default empty environment variables are considered unset and will fall back to the next configuration source. To treat empty environment variables as set, use the AllowEmptyEnv method.

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.

For individual flags, 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"))

You can also bind an existing set of pflags (pflag.FlagSet):

Example:

pflag.Int("flagname", 1234, "help message for flagname")

pflag.Parse()
viper.BindPFlags(pflag.CommandLine)

i := viper.GetInt("flagname") // retrieve values from viper instead of pflag

The use of pflag in Viper does not preclude the use of other packages that use the flag package from the standard library. The pflag package can handle the flags defined for the flag package by importing these flags. This is accomplished by a calling a convenience function provided by the pflag package called AddGoFlagSet().

Example:

package main

import (
	"flag"
	"github.com/spf13/pflag"
)

func main() {

	// using standard library "flag" package
	flag.Int("flagname", 1234, "help message for flagname")

	pflag.CommandLine.AddGoFlagSet(flag.CommandLine)
	pflag.Parse()
	viper.BindPFlags(pflag.CommandLine)

	i := viper.GetInt("flagname") // retrieve value from viper

	// ...
}
Flag interfaces

Viper provides two Go interfaces to bind other flag systems if you don’t use Pflags.

FlagValue represents a single flag. This is a very simple example on how to implement this interface:

type myFlag struct {}
func (f myFlag) HasChanged() bool { return false }
func (f myFlag) Name() string { return "my-flag-name" }
func (f myFlag) ValueString() string { return "my-flag-value" }
func (f myFlag) ValueType() string { return "string" }

Once your flag implements this interface, you can simply tell Viper to bind it:

viper.BindFlagValue("my-flag-name", myFlag{})

FlagValueSet represents a group of flags. This is a very simple example on how to implement this interface:

type myFlagSet struct {
	flags []myFlag
}

func (f myFlagSet) VisitAll(fn func(FlagValue)) {
	for _, flag := range flags {
		fn(flag)
	}
}

Once your flag set implements this interface, you can simply tell Viper to bind it:

fSet := myFlagSet{
	flags: []myFlag{myFlag{}, myFlag{}},
}
viper.BindFlagValues("my-flags", fSet)

Remote Key/Value Store Support

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, YAML, HCL or envfile) 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 supports multiple hosts. To use, pass a list of endpoints separated by ;. For example http://127.0.0.1:4001;http://127.0.0.1:4002.

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/bketelsen/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

etcd
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, supported extensions are "json", "toml", "yaml", "yml", "properties", "props", "prop", "env", "dotenv"
err := viper.ReadRemoteConfig()
etcd3
viper.AddRemoteProvider("etcd3", "http://127.0.0.1:4001","/config/hugo.json")
viper.SetConfigType("json") // because there is no file extension in a stream of bytes, supported extensions are "json", "toml", "yaml", "yml", "properties", "props", "prop", "env", "dotenv"
err := viper.ReadRemoteConfig()
Consul

You need to set a key to Consul key/value storage with JSON value containing your desired config. For example, create a Consul key/value store key MY_CONSUL_KEY with value:

{
    "port": 8080,
    "hostname": "myhostname.com"
}

viper.AddRemoteProvider("consul", "localhost:8500", "MY_CONSUL_KEY")
viper.SetConfigType("json") // Need to explicitly set this to json
err := viper.ReadRemoteConfig()

fmt.Println(viper.Get("port")) // 8080
fmt.Println(viper.Get("hostname")) // myhostname.com
Firestore
viper.AddRemoteProvider("firestore", "google-cloud-project-id", "collection/document")
viper.SetConfigType("json") // Config's format: "json", "toml", "yaml", "yml"
err := viper.ReadRemoteConfig()

Of course, you're allowed to use SecureRemoteProvider also

NATS
viper.AddRemoteProvider("nats", "nats://127.0.0.1:4222", "myapp.config")
viper.SetConfigType("json")
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,  supported extensions are "json", "toml", "yaml", "yml", "properties", "props", "prop", "env", "dotenv"
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, supported extensions are "json", "toml", "yaml", "yml", "properties", "props", "prop", "env", "dotenv"

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

// unmarshal config
runtime_viper.Unmarshal(&runtime_conf)

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

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

		// unmarshal 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.Unmarshal(&runtime_conf)
	}
}()

Getting Values From Viper

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) : any
  • GetBool(key string) : bool
  • GetFloat64(key string) : float64
  • GetInt(key string) : int
  • GetIntSlice(key string) : []int
  • GetString(key string) : string
  • GetStringMap(key string) : map[string]any
  • GetStringMapString(key string) : map[string]string
  • GetStringSlice(key string) : []string
  • GetTime(key string) : time.Time
  • GetDuration(key string) : time.Duration
  • IsSet(key string) : bool
  • AllSettings() : map[string]any

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.

The zero value will also be returned if the value is set, but fails to parse as the requested type.

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 precedence rules established above; the search for the path will cascade through the remaining configuration registries until found.

For example, given this configuration file, both datastore.metric.host and datastore.metric.port are already defined (and may be overridden). If in addition datastore.metric.protocol was defined in the defaults, Viper would also find it.

However, if datastore.metric was overridden (by a flag, an environment variable, the Set() method, …) with an immediate value, then all sub-keys of datastore.metric become undefined, they are “shadowed” by the higher-priority configuration level.

Viper can access array indices by using numbers in the path. For example:

{
    "host": {
        "address": "localhost",
        "ports": [
            5799,
            6029
        ]
    },
    "datastore": {
        "metric": {
            "host": "127.0.0.1",
            "port": 3099
        },
        "warehouse": {
            "host": "198.0.0.1",
            "port": 2112
        }
    }
}

GetInt("host.ports.1") // returns 6029

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"

Extracting a sub-tree

When developing reusable modules, it's often useful to extract a subset of the configuration and pass it to a module. This way the module can be instantiated more than once, with different configurations.

For example, an application might use multiple different cache stores for different purposes:

cache:
  cache1:
    max-items: 100
    item-size: 64
  cache2:
    max-items: 200
    item-size: 80

We could pass the cache name to a module (eg. NewCache("cache1")), but it would require weird concatenation for accessing config keys and would be less separated from the global config.

So instead of doing that let's pass a Viper instance to the constructor that represents a subset of the configuration:

cache1Config := viper.Sub("cache.cache1")
if cache1Config == nil { // Sub returns nil if the key cannot be found
	panic("cache configuration not found")
}

cache1 := NewCache(cache1Config)

Note: Always check the return value of Sub. It returns nil if a key cannot be found.

Internally, the NewCache function can address max-items and item-size keys directly:

func NewCache(v *Viper) *Cache {
	return &Cache{
		MaxItems: v.GetInt("max-items"),
		ItemSize: v.GetInt("item-size"),
	}
}

The resulting code is easy to test, since it's decoupled from the main config structure, and easier to reuse (for the same reason).

Unmarshaling

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

There are two methods to do this:

  • Unmarshal(rawVal any) : error
  • UnmarshalKey(key string, rawVal any) : error

Example:

type config struct {
	Port int
	Name string
	PathMap string `mapstructure:"path_map"`
}

var C config

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

If you want to unmarshal configuration where the keys themselves contain dot (the default key delimiter), you have to change the delimiter:

v := viper.NewWithOptions(viper.KeyDelimiter("::"))

v.SetDefault("chart::values", map[string]any{
	"ingress": map[string]any{
		"annotations": map[string]any{
			"traefik.frontend.rule.type":                 "PathPrefix",
			"traefik.ingress.kubernetes.io/ssl-redirect": "true",
		},
	},
})

type config struct {
	Chart struct{
		Values map[string]any
	}
}

var C config

v.Unmarshal(&C)

Viper also supports unmarshaling into embedded structs:

/*
Example config:

module:
    enabled: true
    token: 89h3f98hbwf987h3f98wenf89ehf
*/
type config struct {
	Module struct {
		Enabled bool

		moduleConfig `mapstructure:",squash"`
	}
}

// moduleConfig could be in a module specific package
type moduleConfig struct {
	Token string
}

var C config

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

Viper uses github.com/mitchellh/mapstructure under the hood for unmarshaling values which uses mapstructure tags by default.

Decoding custom formats

A frequently requested feature for Viper is adding more value formats and decoders. For example, parsing character (dot, comma, semicolon, etc) separated strings into slices.

This is already available in Viper using mapstructure decode hooks.

Read more about the details in this blog post.

Marshalling to string

You may need to marshal all the settings held in viper into a string rather than write them to a file. You can use your favorite format's marshaller with the config returned by AllSettings().

import (
	yaml "gopkg.in/yaml.v2"
	// ...
)

func yamlStringSettings() string {
	c := viper.AllSettings()
	bs, err := yaml.Marshal(c)
	if err != nil {
		log.Fatalf("unable to marshal config to YAML: %v", err)
	}
	return string(bs)
}

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 its 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

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.

Why is it called “Cobra”?

Is there a better name for a commander?

Does Viper support case sensitive keys?

tl;dr: No.

Viper merges configuration from various sources, many of which are either case insensitive or uses different casing than the rest of the sources (eg. env vars). In order to provide the best experience when using multiple sources, the decision has been made to make all keys case insensitive.

There has been several attempts to implement case sensitivity, but unfortunately it's not that trivial. We might take a stab at implementing it in Viper v2, but despite the initial noise, it does not seem to be requested that much.

You can vote for case sensitivity by filling out this feedback form: https://forms.gle/R6faU74qPRPAzchZ9

Is it safe to concurrently read and write to a viper?

No, you will need to synchronize access to the viper yourself (for example by using the sync package). Concurrent reads and writes can cause a panic.

Troubleshooting

See TROUBLESHOOTING.md.

Development

For an optimal developer experience, it is recommended to install Nix and direnv.

Alternatively, install Go on your computer then run make deps to install the rest of the dependencies.

Run the test suite:

make test

Run linters:

make lint # pass -j option to run them in parallel

Some linter violations can automatically be fixed:

make fmt

License

The project is licensed under the MIT License.

Documentation

Index

Constants

This section is empty.

Variables

View Source 
var RemoteConfig remoteConfigFactory

RemoteConfig is optional, see the remote package.

View Source 
var SupportedExts = []string{"json", "toml", "yaml", "yml", "properties", "props", "prop", "hcl", "tfvars", "dotenv", "env", "ini"}

SupportedExts are universally supported extensions.

View Source 
var SupportedRemoteProviders = []string{"etcd", "etcd3", "consul", "firestore", "nats"}

SupportedRemoteProviders are universally supported remote providers.

Functions

func AddConfigPath 

func AddConfigPath(in string)

AddConfigPath adds 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", "etcd3", "consul", "firestore" or "nats" are currently supported. endpoint is the url. etcd requires http://ip:port, consul requires ip:port, nats requires nats://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", "etcd3", "consul", "firestore" or "nats" 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/bketelsen/crypt.

func AllKeys 

func AllKeys() []string

AllKeys returns all keys holding a value, regardless of where they are set. Nested keys are returned with a v.keyDelim separator.

func AllSettings 

func AllSettings() map[string]any

AllSettings merges all settings and returns them as a map[string]any.

func AllowEmptyEnv added in v1.3.0 

func AllowEmptyEnv(allowEmptyEnv bool)

AllowEmptyEnv tells Viper to consider set, but empty environment variables as valid values instead of falling back. For backward compatibility reasons this is false by default.

func AutomaticEnv 

func AutomaticEnv()

AutomaticEnv makes Viper check if environment variables match any of the existing keys (config, default or flags). If matching env vars are found, they are loaded into Viper.

func BindEnv 

func BindEnv(input ...string) error

BindEnv 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. If more arguments are provided, they will represent the env variable names that should bind to this key and will be taken in the specified order. EnvPrefix will be used when set when env name is not provided.

func BindFlagValue 

func BindFlagValue(key string, flag FlagValue) error

BindFlagValue binds a specific key to a FlagValue.

func BindFlagValues 

func BindFlagValues(flags FlagValueSet) error

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

func BindPFlag 

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

BindPFlag binds a specific key to a pflag (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) error

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

func ConfigFileUsed 

func ConfigFileUsed() string

ConfigFileUsed returns the file used to populate the config registry.

func Debug 

func Debug()

Debug prints all configuration registries for debugging purposes.

func DebugTo added in v1.13.0 

func DebugTo(w io.Writer)

func Get 

func Get(key string) any

Get can retrieve any value given the key to use. Get is case-insensitive for a key. 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

GetBool returns the value associated with the key as a boolean.

func GetDuration 

func GetDuration(key string) time.Duration

GetDuration returns the value associated with the key as a duration.

func GetEnvPrefix added in v1.17.0 

func GetEnvPrefix() string

func GetFloat64 

func GetFloat64(key string) float64

GetFloat64 returns the value associated with the key as a float64.

func GetInt 

func GetInt(key string) int

GetInt returns the value associated with the key as an integer.

func GetInt32 added in v1.1.0 

func GetInt32(key string) int32

GetInt32 returns the value associated with the key as an integer.

func GetInt64 

func GetInt64(key string) int64

GetInt64 returns the value associated with the key as an integer.

func GetIntSlice added in v1.5.0 

func GetIntSlice(key string) []int

GetIntSlice returns the value associated with the key as a slice of int values.

func GetSizeInBytes 

func GetSizeInBytes(key string) uint

GetSizeInBytes returns the size of the value associated with the given key in bytes.

func GetString 

func GetString(key string) string

GetString returns the value associated with the key as a string.

func GetStringMap 

func GetStringMap(key string) map[string]any

GetStringMap returns the value associated with the key as a map of interfaces.

func GetStringMapString 

func GetStringMapString(key string) map[string]string

GetStringMapString returns the value associated with the key as a map of strings.

func GetStringMapStringSlice 

func GetStringMapStringSlice(key string) map[string][]string

GetStringMapStringSlice returns the value associated with the key as a map to a slice of strings.

func GetStringSlice 

func GetStringSlice(key string) []string

GetStringSlice returns the value associated with the key as a slice of strings.

func GetTime 

func GetTime(key string) time.Time

GetTime returns the value associated with the key as time.

func GetUint added in v1.4.0 

func GetUint(key string) uint

GetUint returns the value associated with the key as an unsigned integer.

func GetUint16 added in v1.13.0 

func GetUint16(key string) uint16

GetUint16 returns the value associated with the key as an unsigned integer.

func GetUint32 added in v1.4.0 

func GetUint32(key string) uint32

GetUint32 returns the value associated with the key as an unsigned integer.

func GetUint64 added in v1.4.0 

func GetUint64(key string) uint64

GetUint64 returns the value associated with the key as an unsigned integer.

func InConfig 

func InConfig(key string) bool

InConfig checks to see if the given key (or an alias) is in the config file.

func IsSet 

func IsSet(key string) bool

IsSet checks to see if the key has been set in any of the data locations. IsSet is case-insensitive for a key.

func MergeConfig 

func MergeConfig(in io.Reader) error

MergeConfig merges a new configuration with an existing config.

func MergeConfigMap added in v1.3.0 

func MergeConfigMap(cfg map[string]any) error

MergeConfigMap merges the configuration from the map given with an existing config. Note that the map given may be modified.

func MergeInConfig 

func MergeInConfig() error

MergeInConfig merges a new configuration with an existing config.

func MustBindEnv added in v1.12.0 

func MustBindEnv(input ...string)

MustBindEnv wraps BindEnv in a panic. If there is an error binding an environment variable, MustBindEnv will panic.

func OnConfigChange 

func OnConfigChange(run func(in fsnotify.Event))

OnConfigChange sets the event handler that is called when a config file changes.

func ReadConfig 

func ReadConfig(in io.Reader) error

ReadConfig will read a configuration file, setting existing keys to nil if the key does not exist in the file.

func ReadInConfig 

func ReadInConfig() error

ReadInConfig 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

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

func RegisterAlias 

func RegisterAlias(alias, key string)

RegisterAlias creates an alias that provides another accessor for the same key. This enables one to change a name without breaking the application.

func Reset 

func Reset()

Reset is 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 SafeWriteConfig added in v1.0.1 

func SafeWriteConfig() error

SafeWriteConfig writes current configuration to file only if the file does not exist.

func SafeWriteConfigAs added in v1.0.1 

func SafeWriteConfigAs(filename string) error

SafeWriteConfigAs writes current configuration to a given filename if it does not exist.

func Set 

func Set(key string, value any)

Set sets the value for the key in the override register. Set is case-insensitive for a key. Will be used instead of values obtained via flags, config file, ENV, default, or key/value store.

func SetConfigFile 

func SetConfigFile(in string)

SetConfigFile explicitly defines 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)

SetConfigName sets name for the config file. Does not include extension.

func SetConfigPermissions added in v1.4.0 

func SetConfigPermissions(perm os.FileMode)

SetConfigPermissions sets the permissions for the config file.

func SetConfigType 

func SetConfigType(in string)

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

func SetDefault 

func SetDefault(key string, value any)

SetDefault sets the default value for this key. SetDefault is case-insensitive for a 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)

SetEnvPrefix defines 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 SetFs 

func SetFs(fs afero.Fs)

SetFs sets the filesystem to use to read configuration.

func SetTypeByDefaultValue 

func SetTypeByDefaultValue(enable bool)

SetTypeByDefaultValue enables or disables the inference of a key value's type when the Get function is used based upon a key's default value as opposed to the value returned based on the normal fetch logic.

For example, if a key has a default value of []string{} and the same key is set via an environment variable to "a b c", a call to the Get function would return a string slice for the key if the key's type is inferred by the default value and the Get function would return: 

[]string {"a", "b", "c"}

Otherwise the Get function would return: 

"a b c"

func Unmarshal 

func Unmarshal(rawVal any, opts ...DecoderConfigOption) error

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

func UnmarshalExact added in v1.6.0 

func UnmarshalExact(rawVal any, opts ...DecoderConfigOption) error

UnmarshalExact unmarshals the config into a Struct, erroring if a field is nonexistent in the destination struct.

func UnmarshalKey 

func UnmarshalKey(key string, rawVal any, opts ...DecoderConfigOption) error

UnmarshalKey takes a single key and unmarshals it into a Struct.

func WatchConfig 

func WatchConfig()

WatchConfig starts watching a config file for changes.

func WatchRemoteConfig 

func WatchRemoteConfig() error

func WriteConfig added in v1.0.1 

func WriteConfig() error

WriteConfig writes the current configuration to a file.

func WriteConfigAs added in v1.0.1 

func WriteConfigAs(filename string) error

WriteConfigAs writes current configuration to a given filename.

Types

type ConfigFileAlreadyExistsError added in v1.6.0 

type ConfigFileAlreadyExistsError string

ConfigFileAlreadyExistsError denotes failure to write new configuration file.

func (ConfigFileAlreadyExistsError) Error added in v1.6.0 

func (faee ConfigFileAlreadyExistsError) Error() string

Error returns the formatted error when configuration already exists.

type ConfigFileNotFoundError 

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

ConfigFileNotFoundError denotes failing to find configuration file.

func (ConfigFileNotFoundError) Error 

func (fnfe ConfigFileNotFoundError) Error() string

Error returns the formatted configuration error.

type ConfigMarshalError added in v1.0.1 

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

ConfigMarshalError happens when failing to marshal the configuration.

func (ConfigMarshalError) Error added in v1.0.1 

func (e ConfigMarshalError) Error() string

Error returns the formatted configuration error.

type ConfigParseError 

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

ConfigParseError denotes failing to parse configuration file.

func (ConfigParseError) Error 

func (pe ConfigParseError) Error() string

Error returns the formatted configuration error.

func (ConfigParseError) Unwrap added in v1.16.0 

func (pe ConfigParseError) Unwrap() error

Unwrap returns the wrapped error.

type DecoderConfigOption added in v1.1.0 

type DecoderConfigOption func(*mapstructure.DecoderConfig)

A DecoderConfigOption can be passed to viper.Unmarshal to configure mapstructure.DecoderConfig options.

func DecodeHook added in v1.1.0 

func DecodeHook(hook mapstructure.DecodeHookFunc) DecoderConfigOption

DecodeHook returns a DecoderConfigOption which overrides the default DecoderConfig.DecodeHook value, the default is: 

 mapstructure.ComposeDecodeHookFunc(
		mapstructure.StringToTimeDurationHookFunc(),
		mapstructure.StringToSliceHookFunc(","),
	)

type FlagValue 

type FlagValue interface {
	HasChanged() bool
	Name() string
	ValueString() string
	ValueType() string
}

FlagValue is an interface that users can implement to bind different flags to viper.

type FlagValueSet 

type FlagValueSet interface {
	VisitAll(fn func(FlagValue))
}

FlagValueSet is an interface that users can implement to bind a set of flags to viper.

type Logger deprecated added in v1.10.0 

type Logger interface {
	// Trace logs a Trace event.
	//
	// Even more fine-grained information than Debug events.
	// Loggers not supporting this level should fall back to Debug.
	Trace(msg string, keyvals ...any)

	// Debug logs a Debug event.
	//
	// A verbose series of information events.
	// They are useful when debugging the system.
	Debug(msg string, keyvals ...any)

	// Info logs an Info event.
	//
	// General information about what's happening inside the system.
	Info(msg string, keyvals ...any)

	// Warn logs a Warn(ing) event.
	//
	// Non-critical events that should be looked at.
	Warn(msg string, keyvals ...any)

	// Error logs an Error event.
	//
	// Critical events that require immediate attention.
	// Loggers commonly provide Fatal and Panic levels above Error level,
	// but exiting and panicking is out of scope for a logging library.
	Error(msg string, keyvals ...any)
}

Logger is a unified interface for various logging use cases and practices, including:

  • leveled logging
  • structured logging

Deprecated: use `log/slog` instead.

type Option added in v1.6.0 

type Option interface {
	// contains filtered or unexported methods
}

Option configures Viper using the functional options paradigm popularized by Rob Pike and Dave Cheney. If you're unfamiliar with this style, see https://commandcenter.blogspot.com/2014/01/self-referential-functions-and-design.html and https://dave.cheney.net/2014/10/17/functional-options-for-friendly-apis.

func EnvKeyReplacer added in v1.6.0 

func EnvKeyReplacer(r StringReplacer) Option

EnvKeyReplacer sets a replacer used for mapping environment variables to internal keys.

func IniLoadOptions added in v1.8.0 

func IniLoadOptions(in ini.LoadOptions) Option

IniLoadOptions sets the load options for ini parsing.

func KeyDelimiter added in v1.6.0 

func KeyDelimiter(d string) Option

KeyDelimiter sets the delimiter used for determining key parts. By default it's value is ".".

func WithLogger added in v1.17.0 

func WithLogger(l *slog.Logger) Option

WithLogger sets a custom logger.

type RemoteConfigError 

type RemoteConfigError string

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

func (RemoteConfigError) Error 

func (rce RemoteConfigError) Error() string

Error returns the formatted remote provider error.

type RemoteProvider 

type RemoteProvider interface {
	Provider() string
	Endpoint() string
	Path() string
	SecretKeyring() string
}

RemoteProvider stores the configuration necessary to connect to a remote key/value store. Optional secretKeyring to unencrypt encrypted values can be provided.

type RemoteResponse 

type RemoteResponse struct {
	Value []byte
	Error error
}

type StringReplacer added in v1.6.0 

type StringReplacer interface {
	// Replace returns a copy of s with all replacements performed.
	Replace(s string) string
}

StringReplacer applies a set of replacements to a string.

type UnsupportedConfigError 

type UnsupportedConfigError string

UnsupportedConfigError denotes encountering an unsupported configuration filetype.

func (UnsupportedConfigError) Error 

func (str UnsupportedConfigError) Error() string

Error returns the formatted configuration error.

type UnsupportedRemoteProviderError 

type UnsupportedRemoteProviderError string

UnsupportedRemoteProviderError denotes encountering an unsupported remote provider. Currently only etcd and Consul are supported.

func (UnsupportedRemoteProviderError) Error 

func (str UnsupportedRemoteProviderError) Error() string

Error 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"
}

Note: Vipers are not safe for concurrent Get() and Set() operations.

func GetViper 

func GetViper() *Viper

GetViper gets the global Viper instance.

func New 

func New() *Viper

New returns an initialized Viper instance.

func NewWithOptions added in v1.6.0 

func NewWithOptions(opts ...Option) *Viper

NewWithOptions creates a new Viper instance.

func Sub 

func Sub(key string) *Viper

Sub returns new Viper instance representing a sub tree of this instance. Sub is case-insensitive for a key.

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]any

func (*Viper) AllowEmptyEnv added in v1.3.0 

func (v *Viper) AllowEmptyEnv(allowEmptyEnv bool)

func (*Viper) AutomaticEnv 

func (v *Viper) AutomaticEnv()

func (*Viper) BindEnv 

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

func (*Viper) BindFlagValue 

func (v *Viper) BindFlagValue(key string, flag FlagValue) error

func (*Viper) BindFlagValues 

func (v *Viper) BindFlagValues(flags FlagValueSet) (err error)

func (*Viper) BindPFlag 

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

func (*Viper) BindPFlags 

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

func (*Viper) ConfigFileUsed 

func (v *Viper) ConfigFileUsed() string

func (*Viper) Debug 

func (v *Viper) Debug()

func (*Viper) DebugTo added in v1.13.0 

func (v *Viper) DebugTo(w io.Writer)

func (*Viper) Get 

func (v *Viper) Get(key string) any

func (*Viper) GetBool 

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

func (*Viper) GetDuration 

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

func (*Viper) GetEnvPrefix added in v1.17.0 

func (v *Viper) GetEnvPrefix() string

func (*Viper) GetFloat64 

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

func (*Viper) GetInt 

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

func (*Viper) GetInt32 added in v1.1.0 

func (v *Viper) GetInt32(key string) int32

func (*Viper) GetInt64 

func (v *Viper) GetInt64(key string) int64

func (*Viper) GetIntSlice added in v1.5.0 

func (v *Viper) GetIntSlice(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]any

func (*Viper) GetStringMapString 

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

func (*Viper) GetStringMapStringSlice 

func (v *Viper) GetStringMapStringSlice(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) GetUint added in v1.4.0 

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

func (*Viper) GetUint16 added in v1.13.0 

func (v *Viper) GetUint16(key string) uint16

func (*Viper) GetUint32 added in v1.4.0 

func (v *Viper) GetUint32(key string) uint32

func (*Viper) GetUint64 added in v1.4.0 

func (v *Viper) GetUint64(key string) uint64

func (*Viper) InConfig 

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

func (*Viper) IsSet 

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

func (*Viper) MergeConfig 

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

func (*Viper) MergeConfigMap added in v1.3.0 

func (v *Viper) MergeConfigMap(cfg map[string]any) error

func (*Viper) MergeInConfig 

func (v *Viper) MergeInConfig() error

func (*Viper) MustBindEnv added in v1.12.0 

func (v *Viper) MustBindEnv(input ...string)

func (*Viper) OnConfigChange 

func (v *Viper) OnConfigChange(run func(in fsnotify.Event))

OnConfigChange sets the event handler that is called when a config file changes.

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, key string)

func (*Viper) SafeWriteConfig added in v1.0.1 

func (v *Viper) SafeWriteConfig() error

func (*Viper) SafeWriteConfigAs added in v1.0.1 

func (v *Viper) SafeWriteConfigAs(filename string) error

func (*Viper) Set 

func (v *Viper) Set(key string, value any)

func (*Viper) SetConfigFile 

func (v *Viper) SetConfigFile(in string)

func (*Viper) SetConfigName 

func (v *Viper) SetConfigName(in string)

func (*Viper) SetConfigPermissions added in v1.4.0 

func (v *Viper) SetConfigPermissions(perm os.FileMode)

func (*Viper) SetConfigType 

func (v *Viper) SetConfigType(in string)

func (*Viper) SetDefault 

func (v *Viper) SetDefault(key string, value any)

func (*Viper) SetEnvKeyReplacer 

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

func (*Viper) SetEnvPrefix 

func (v *Viper) SetEnvPrefix(in string)

func (*Viper) SetFs 

func (v *Viper) SetFs(fs afero.Fs)

func (*Viper) SetTypeByDefaultValue 

func (v *Viper) SetTypeByDefaultValue(enable bool)

func (*Viper) Sub 

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

func (*Viper) Unmarshal 

func (v *Viper) Unmarshal(rawVal any, opts ...DecoderConfigOption) error

func (*Viper) UnmarshalExact 

func (v *Viper) UnmarshalExact(rawVal any, opts ...DecoderConfigOption) error

func (*Viper) UnmarshalKey 

func (v *Viper) UnmarshalKey(key string, rawVal any, opts ...DecoderConfigOption) error

func (*Viper) WatchConfig 

func (v *Viper) WatchConfig()

WatchConfig starts watching a config file for changes.

func (*Viper) WatchRemoteConfig 

func (v *Viper) WatchRemoteConfig() error

func (*Viper) WatchRemoteConfigOnChannel 

func (v *Viper) WatchRemoteConfigOnChannel() error

func (*Viper) WriteConfig added in v1.0.1 

func (v *Viper) WriteConfig() error

func (*Viper) WriteConfigAs added in v1.0.1 

func (v *Viper) WriteConfigAs(filename string) error

Source Files

View all Source files

Directories

Path Synopsis
internal
encoding
encoding/dotenv
encoding/hcl
encoding/ini
encoding/javaproperties
encoding/json
encoding/toml
encoding/yaml
features
testutil
Package remote integrates the remote features of Viper.
 Package remote integrates the remote features of Viper.

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