onion

Layer based configuration for golang

Programming language: Go

License: MIT License

Tags: Configuration    

Latest version: v0.1.3

README

onion

import "github.com/goraz/onion"

Package onion is a layer based, pluggable config manager for golang.

The current version in develop branch is work in progress (see the milestone), for older versions check the v2 and v3 branches and use the gopkg.in/goraz/onion.v1 and gopkg.in/goraz/onion.v2 For the next release we use the go module and tagging using semantic version.

Shrek: For your information, there's a lot more to ogres than people think.
Donkey: Example?
Shrek: Example... uh... ogres are like onions! 
[holds up an onion, which Donkey sniffs] 
Donkey: They stink? 
Shrek: Yes... No! 
Donkey: Oh, they make you cry? 
Shrek: No! 
Donkey: Oh, you leave 'em out in the sun, they get all brown, start sproutin' little white hairs...
Shrek: [peels an onion] NO! Layers. Onions have layers. Ogres have layers... You get it? We both have layers.
[walks off]
Donkey: Oh, you both have LAYERS. Oh. You know, not everybody like onions. CAKE! Everybody loves cake! Cakes have layers!
Shrek: I don't care what everyone likes! Ogres are not like cakes.
Donkey: You know what ELSE everybody likes? Parfaits! Have you ever met a person, you say, "Let's get some parfait," they say, "Hell no, I don't like no parfait."? Parfaits are delicious!
Shrek: NO! You dense, irritating, miniature beast of burden! Ogres are like onions! End of story! Bye-bye! See ya later.
Donkey: Parfait's gotta be the most delicious thing on the whole damn planet! 

Goals

The main goal is to have minimal dependency based on usage. if you need normal config files in the file system, there should be no dependency to etcd or consul, if you have only yaml files, including toml or any other format is just not right.

Usage

Choose the layer first. normal file layer and json are built-in but for any other type you need to import the package for that layer.

Example json file layer

package main

import (
    "fmt"

    "github.com/goraz/onion"
)

func main() {
    // Create a file layer to load data from json file. onion loads the file based on the extension.
    // so the json file should have `.json` ext.
    l1, err := onion.NewFileLayer("/etc/shared.json", nil)
    if err != nil {
        panic(err)
    }

    // Create a layer based on the environment. it loads every environment with APP_ prefix
    // for example APP_TEST_STRING is available as o.Get("test.string")
    l2 := onion.NewEnvLayerPrefix("_", "APP")

    // Create the onion, the final result is union of l1 and l2 but l2 overwrite l1.
    o := onion.New(l1, l2)
    str := o.GetStringDefault("test.string", "empty")
    fmt.Println(str)
    // Now str is the string in this order
    // 1- if the APP_TEST_STRING is available in the env
    // 2- if the shared.json had key like this { "test" : { "string" : "value" }} then the str is "value"
    // 3- the provided default, "empty"
}

Loading other file format

Currently onion support json format out-of-the-box, while you need to blank import the loader package of others formats to use them:

• toml (for 0.4.0 version)
• toml-0.5.0 (for 0.5.0 version)
• yaml
• properties

For example:

import (
    _ "github.com/goraz/onion/loaders/toml" // Needed to load TOML format
)

Watch file and etcd

Also there is other layers, (like etcd and filewatchlayer) that watches for change.

package main

import (
    "fmt"

    "github.com/goraz/onion"
    "github.com/goraz/onion/layers/etcdlayer"
    "github.com/goraz/onion/layers/filewatchlayer"
)

func main() {
    // Create a file layer to load data from json file. also it watches for change in the file
    l1, err := filewatchlayer.NewFileWatchLayer("/etc/shared.json", nil)
    if err != nil {
        panic(err)
    }

    l2, err := etcdlayer.NewEtcdLayer("/app/config", "json", []string{"http://127.0.0.1:2379"}, nil)
    if err != nil {
        panic(err)
    }

    // Create the onion, the final result is union of l1 and l2 but l2 overwrite l1.
    o := onion.New(l1, l2)
    // Get the latest version of the key 
    str := o.GetStringDefault("test.string", "empty")
    fmt.Println(str)
}

Encrypted config

Also if you want to store data in encrypted content. currently only secconf (based on the crypt project) is supported. also the onioncli helps you to manage this keys.

package main

import (
    "bytes"
    "fmt"

    "github.com/goraz/onion"
    "github.com/goraz/onion/ciphers/secconf"
    "github.com/goraz/onion/layers/etcdlayer"
    "github.com/goraz/onion/layers/filewatchlayer"
)

// Normally this should be in a safe place, not here
const privateKey = `PRIVATE KEY`

func main() {
    // The private key should be in the safe place. this is just a demo, also there is a cli tool
    // to create this `go get -u github.com/goraz/onion/cli/onioncli`
    cipher, err := secconf.NewCipher(bytes.NewReader([]byte(privateKey)))
    if err != nil {
        panic(err)
    }

    // Create a file layer to load data from json file. also it watches for change in the file
    // passing the cipher to this make means the file in base64 and pgp encrypted
    l1, err := filewatchlayer.NewFileWatchLayer("/etc/shared.json", cipher)
    if err != nil {
        panic(err)
    }

    // Create a etcd layer. it watches the /app/config key and it should be json file encoded with
    // base64 and pgp
    l2, err := etcdlayer.NewEtcdLayer("/app/config", "json", []string{"http://127.0.0.1:2379"}, cipher)
    if err != nil {
        panic(err)
    }

    // Create the onion, the final result is union of l1 and l2 but l2 overwrites l1.
    o := onion.New(l1, l2)
    // Get the latest version of the key
    str := o.GetStringDefault("test.string", "empty")
    fmt.Println(str)
}