Flatcfg

Simple, easy-to-use clojure library for configure projects. Because smart things must be handled by admins or devops.

Configuration supports three sources, resolved in the following order:

1. Command-line args
2. From environment by environ library.
3. Config-file

Installation

[flatcfg "0.1.1"]

Usage

Main point is equal config key from any source. For example

• AUTH_TWITTER_KEY=val from ENV is equal to
• -Dauth.twitter.key=val from Java system properties is equal to
• auth-twitter-key val from command line is equal to
• {:auth {:twitter {:key "val"}}} from config file is equal to
• {:auth-twitter-key "val"} from another config file.

And it can be accessed by simple api:

(get! :auth-twitter-key)
;; or
(get-in! :auth :twitter :key)

• As environ does all keys from command-line, args are lowercased, characters "_" and "." replaced by "-" and converted to keyword.

• By default flatcfg will try to read config from config.edn in same directory where jar file or lein project are located.

• Config file location can be set by config parameter in ENV or in cmd-args. If it found, flatcfg will read it automatically.

API

• (get! key [default]) → config value
• (get-in! [& args]) → config value
• (get key [default]) → same as (delay (get! key [default])
• (get-in [& args]) → same Delay object
• (consume-args [args]) ← load args as command-line args
• (load-config-file [filename]) ← load config from file

Delay object is required if we want to define config value at top-level side but config will not be ready yet because it is filled later by consume-args for example.

Nested structure in config file

A key in nested structure at EDN config file can be accessed by the key with "-" as separate character. For example for this config file:

{:auth {:twitter {:key "super-secret-key-here"}}}

(get! :auth-twitter-key)
;; the same as
(get-in! :auth :twitter :key)

BTW, AUTH_TWITTER_KEY=my-secret-here java -jar app.jar will work in the same way as config file, see below.

Config examples

All config examples from below are equal.

• From command-line arguments: java -jar app-standalone.jar db-name testing
• From environment by environ:
• DB_NAME=testing java -jar app-standalone.jar
• java -Ddb.name=testing -jar app-standalone.jar
• Advanced usage at environ site, for example consume settings from the Leiningen project map.
• From EDN config file

{:db {:name "testing"}}

• Or in that way

{:db-name "testing"}}

Code example

(ns main
 (:require  [clojure.java.io :as io]
            [flatcfg :as cfg])
 (:gen-class))

(defn -main [& args]
  (cfg/consume-args args)
  ;; if we want not default behaviour
  (cfg/load-config-file (io/resource "config.edn"))
  (my-service/start))

(ns my-service
  (:require [flatcfg :as cfg]))

(def my-secret-key (cfg/get-in :auth :secret-key))

(defn auth! []
  (use-my-secret @my-secret-key))

License

Copyright © 2015 Sergey Rublev

Distributed under the MIT License.