Go Flexible Configuration

Go package providing a uniform interface to configuration, independent of how or where that configuration is defined.

Installation

Install the package using standard GO package retrieval:

go get github.com/zadoo/flexconfig

Test the installed package by changing directory to $(go env GOPATH)/src/github.com/zadoo/flexconfig and running the following command:

ETCDCTL_ENDPOINTS=0.0.0.0:2379 go test

Change 0.0.0.0 to the IP address of your ectd server to test using a configuration store. Omit the environment variable to test without a configuration store.

Use

In GO files that use configuration, add an import statement as follows:

import "github.com/zadoo/flexconfig"

Quickstart

package main

import (
	"fmt"
	"log"

	"github.com/zadoo/flexconfig"
)

func main() {
	// Connect to the etcd running on the local machine and use a prefix
	// of "/example/" for all property keys accessed by this program.
	cfgstore, err := flexconfig.NewFlexConfigStore(
		flexconfig.FlexConfigStoreEtcd,
		[]string{"127.0.0.1:2379"},
		"/example")
	if err != nil {
		log.Print("Failed connecting to config store: ", err)
	}

	// Create Config. Search for config files for the application "example".
	// Convert all environment variables beginning with "EXAMPLE_" to
	// properties. Use a configuration store. Also, all command line
	// variables of the form --<name>=<value> set properties (e.g.
	// --example.log.filepath=/var/log/myapp.log).
	cfg, err := flexconfig.NewFlexibleConfiguration(
		flexconfig.ConfigurationParameters{
			ApplicationName:             "example",
			EnvironmentVariablePrefixes: []string{"EXAMPLE_"},
			ConfigurationStore:          cfgstore,
		})
	if err != nil {
		log.Fatal("Failed creating configuration: ", err)
	}

	logPath := cfg.Get("log.path")
	fmt.Printf("%s = %s\n", "log.path", logPath)

	fooPluginName := cfg.Get("example.plugins.foo.name")
	fmt.Printf("%s = %s\n", "example.plugins.foo.name", fooPluginName)
}

The program can be invoked as follows (assuming it is called main.go):

EXAMPLE_PLUGINS_FOO_NAME=univeral.xyz go run main.go --log.path=/var/xyz/www.log

and it will print:

log.path = /var/xyz/www.log
example.plugins.foo.name = universal.xyz

Alternatively, create a directory named ".example" (this is the application name passed to NewFlexibleConfiguration), and add a file having a suffix of ".conf" (e.g. config.conf) to the directory with the following contents:

log:
  path: /var/xyz/www.log
example:
  plugins:
    foo:
      name: universal.xyz

and invoke it with no arguments or environment variables:

go run main.go

Experiment with a combination of file configuration values, environment variables and command line arguments to see the priority each source has in defining the configuration. Also, omit the application name, or array of environment variable prefixes to control which sources contribute to the final configuration.

If no instance of etcd is available, remove the code to connect to the FlexConfigStore and delete the line setting ConfigurationStore in the request to create a new Config.

Copyright

Copyright (C) 2018-2019 The flexconfig authors.

flexconfig package released under Apache 2.0 License. See LICENSE for details.