aboutsummaryrefslogtreecommitdiff
path: root/vendor/github.com/spf13/viper/README.md
blob: 64bf47435847d3b092866baf49dfa55329027616 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
![viper logo](https://cloud.githubusercontent.com/assets/173412/10886745/998df88a-8151-11e5-9448-4736db51020d.png)

Go configuration with fangs!

Many Go projects are built using Viper including:

* [Hugo](http://gohugo.io)
* [EMC RexRay](http://rexray.readthedocs.org/en/stable/)
* [Imgur’s Incus](https://github.com/Imgur/incus)
* [Nanobox](https://github.com/nanobox-io/nanobox)/[Nanopack](https://github.com/nanopack)
* [Docker Notary](https://github.com/docker/Notary)
* [BloomApi](https://www.bloomapi.com/)
* [doctl](https://github.com/digitalocean/doctl)
* [Clairctl](https://github.com/jgsqware/clairctl)

[![Build Status](https://travis-ci.org/spf13/viper.svg)](https://travis-ci.org/spf13/viper) [![Join the chat at https://gitter.im/spf13/viper](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/spf13/viper?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![GoDoc](https://godoc.org/github.com/spf13/viper?status.svg)](https://godoc.org/github.com/spf13/viper)


## 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, 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, 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

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 it’s useful in the event that a key hasn’t been set via
config file, environment variable, remote configuration or flag.

Examples:

```go
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, 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.

```go
viper.SetConfigName("config") // name of config file (without extension)
viper.AddConfigPath("/etc/appname/")   // path to look for the config file in
viper.AddConfigPath("$HOME/.appname")  // call multiple times to add many search paths
viper.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: %s \n", err))
}
```

### 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()`**

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

### 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.

```go
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.

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

### Registering and Using Aliases

Aliases permit a single value to be referenced by multiple keys

```go
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 working
with ENV:

 * `AutomaticEnv()`
 * `BindEnv(string...) : error`
 * `SetEnvPrefix(string)`
 * `SetEnvKeyReplacer(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. 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.

`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`.

#### Env example

```go
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](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.

For individual flags, the `BindPFlag()` method provides this functionality.

Example:

```go
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:

```go
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](https://github.com/spf13/pflag/) in Viper does not preclude
the use of other packages that use the [flag](https://golang.org/pkg/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:

```go
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:

```go
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:

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

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

```go
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:

```go
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 or HCL) 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.

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.

```bash
$ 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:

```bash
$ 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

```go
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"
err := viper.ReadRemoteConfig()
```

### Remote Key/Value Store Example - Encrypted

```go
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"
err := viper.ReadRemoteConfig()
```

### Watching Changes in etcd - Unencrypted

```go
// 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"

// 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) : 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 a zero
value if it’s not found. To check if a given key exists, the `IsSet()` method
has been provided.

Example:
```go
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:

```json
{
    "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:

```go
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.

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

```json
{
    "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"
```

### Extract sub-tree

Extract sub-tree from Viper.

For example, `viper` represents:

```json
app:
  cache1:
    max-items: 100
    item-size: 64
  cache2:
    max-items: 200
    item-size: 80
```

After executing:

```go
subv := viper.Sub("app.cache1")
```

`subv` represents:

```json
max-items: 100
item-size: 64
```

Suppose we have:

```go
func NewCache(cfg *Viper) *Cache {...}
```

which creates a cache based on config information formatted as `subv`.
Now it’s easy to create these 2 caches separately as:

```go
cfg1 := viper.Sub("app.cache1")
cache1 := NewCache(cfg1)

cfg2 := viper.Sub("app.cache2")
cache2 := NewCache(cfg2)
```

### 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 interface{}) : error`
 * `UnmarshalKey(key string, rawVal interface{}) : error`

Example:

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

var C config

err := Unmarshal(&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 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:

```go
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](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.

Q: Why is it called “Cobra”?

A: Is there a better name for a [commander](http://en.wikipedia.org/wiki/Cobra_Commander)?