Confucius

A Clojure library for composable and declarative configuration.

Suggestions on api, bugfixes, feature request, etc are all very welcome!

Rationale

Applications that require configuration should read values from the environment they live in (see 12factor). Unfortunately this may clutter the application with (Sytem/getenv) calls that return un-typed data. Having all the configuration related data in one handy map that can read properties from the environment and provide sensible default values wherever possible should be the the way to go. This makes it easy to add configuration to version control too!

confucius aims at solving exactly these problems. It builds on some of the ideas from other libraries such as immuconf (composability), nomad, or environ.

Is it used in production?

YES! It's been used in production since late 2015!

Quick Start

The code below show how to use confucius. The files awesome-service.yml, host.edn, subsys.json follow the example.

(ns my.amazing.ns
 (:require
  [confucius.core  :as c]

  ;; If you want support for json and/or yaml you'll need to add
  ;; clojure.data.json or snakeyaml (or both) to your dependencies.
  ;;[confucius.ext.yaml]
  ;;[confucius.ext.json]
  [confucius.ext.all] ; this requires both

  [clojure.java.io :as io]))

(c/load-config
 ;; Why not calling prismatic's schema for validation & complex
 ;; coercion in postprocess?
 {:postprocess-fn identity} ; optional
 [{:global {:tmp-dir "${tmp.dir:/tmp}"}}
  (io/resource "awesome-service.yml")
  "host.edn"])

;; => {:global
;;      {:tmp-dir "/tmp"}
;;
;;     :http
;;      {:bind-address "0.0.0.0"
;;       :port 8080}
;;
;;      :audit-log-dir
;;      "/var/log/service/audit"  ;; assuming ${log-dir} was set to
;;                                ;; `/var/log` in the native environment
;;
;;      :subsys
;;      {:id "subsys1"}}

File contents:

# file: awesome-service.yml (on classpath)
http:
  bind-address: "0.0.0.0"
  port: 80

# Include configuration from `sub-system.json`.
# Supports relative file urls.
subsys: "@:file://./subsys.json"

# Reference (in that order) either
# another value in the configuration,
# a java system property or the native
# enrivonment. Uses `get-in` split at
# `.` to resolve value within the configuration
# map, the value as is for java system
# properties and uppercaseing with `. -> _`
# replacement for native env lookups.
audit-log: "${log-dir}/service/audit"

# file: subsys.json (file system)
{ "id" : "subsys1" }

# file: host.edn
{:http {:port 8080}}

More to come... for an extensive example see the test ns confucius.example_test.clj

See confucius.cli for an example how to integrate command line argument parsing.

Documentation

TBD

Loading

TBD

Composing

TBD

Validation & Coercion

TBD

Extending

TBD

confucius.proto/ValueReader

confucius.proto/ConfigSource

confucius.proto/from-url

TODO

• support printing of configuration map
• warn/log when config properties are being overwritten by other files. use metadata to show where the value came from?

Features? Suggesions? Issues?

Submit bug reports/patches etc through the GitHub repository in the usual way. Cheers!

Contributors

• Fabio Bernasconi (initial design)
• Cedric Roussel (edn support)

License

Copyright © 2015 Fabio Bernasconi

Distributed under the Eclipse Public License, the same as Clojure.