leetconfig

Leetconfig takes your clojure application configuration in different environments into a one singe place. Additionally it gives you the freedom to retrieve parts of configuration differently in different environments. The main idea is to take all the application configuration into a one single place, where you can see all the configuration instantly. Another main driver for this small project was to be able to use AWS EC2 Systems Manager only to certain configuration keys when deployed to AWS. That means, you can fetch configuration values with functions such as (fetch-my-config-value :configuration-key).

Usage should be simple. First argument to leetconfig is the "bootstrap" environment argument which defines the current environment, and second one is the configuration specification map in the following form:

{:configuration-key-1 "direct-default-value"
 :key-2 ["if sequential, first is the default"]
 :key-3 ["default" :env-key "Value, when bootstrapped is :env-key"]
 :key-4 ["default" :env1 "value in env1" :env2 "value in env2" :env3 "value in env3"]
 :key-from-fn my-config-fn ; (defn my-config-fn [key] ... get value for key ... )
 :key-from-fn-2 [my-config-fn] ; wrapped in sequential as well
 :key-from-fn-3 ["default value" :test my-config-fn] ; get it?
 :key-from-fn-4 ["default value" :test "hardcoded test value in test environment" :prod my-config-fn] ; capiche?
 }

Example usage would be something like this:

(def config (leetconfig (env :environment)
                        {:appname "my-leet-app" ; default in all environments
                         :db-host ["localhost"
                                   :test "app-db1-test"
                                   :prod "app-db1-prod"]
                         :db-user ["localuser"
                                   :test "test-db-user"
                                   :prod "prod-db-user"]
                         :db-pass ["localpassword"
                                   :test retrieve-from-crypto-storage
                                   :prod retrieve-from-crypto-storage]}))

This will merely generate a map, with values selected or fetched via provider function

; Calling above like (leetconfig nil ...) or (leetconfig :local ...) will produce a map
(def config {:appname "my-leet-ap"
             :db-host "localhost"
             :db-user "localuser"
             :db-pass "localpassword"})

; Calling with (leetconfig :test ...) will produce
(def config {:appname "my-leet-ap"
             :db-host "app-db1-test"
             :db-user "test-db-user"
             :db-pass "secretsecretsecret"})
; ...when (retrieve-from-crypto-storage :db-pass) returns "secretsecretsecret"

The first argument can be fetched by function or given directly. Whatever suits you. We use environ to fetch it from system environment and start our applications like ENVIRONMENT=test java -jar app.jar, and keep any other environment inside our config namespace.

Take a note, that leetconfig does not enforce how you actually use config map in your application. We use clojure.spec to assert that configuration is actually valid, and then we have something like (defn get-config-value [key] (key config)).

Roadmap

Partial overrides for nested structures

"Partial override" support for nested structures in configuration map, such as:

(def config (leetconfig (env :environment)
                        {:cache-seconds 100
                         :texts [{:name "My application name"
                                  :environment-label "Local environment"}

                                 :test {:environment-label "Test environment"}
                                 :prod {:environment-label "Production environment"}]}))
; Produces in :local|nil
{:cache-seconds 100
 :texts {:name "My application"
         :environment-label "Local environment"}}

; Produces in :test
{:cache-seconds 100
 :texts {:name "My application"
         :environment-label "Test environment"}}

; Produces in :test
{:cache-seconds 100
 :texts {:name "My application"
         :environment-label "Production environment"}}

License

Copyright © 2017 FIXME

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.