I am using monger to fetch and save some data in MongoDb from my Clojure simple app. I have strong Ruby on Rails background so I am familiar with database settings per environment (development, test, production). I want to have something similar in Clojure. How can I add the environment to my code? I want to do it in Clojure-way, code as data, without any yaml files. I am using Leiningen if it changes something.
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3 Answers
You can use Leiningen profiles feature.
In your project.clj define your profiles (most cases you need dev and prod)
:profiles {:dev {:resource-paths ["resource-dev"]} :prod {:resource-paths ["resource-prod"]}} Now create 2 directories resource-dev and resource-prod and create config.clj file in both of them which will have define a map to store configuration. Something like:
(ns myapp.config) (def config {:database "dev"}) Then in your app code you can use below snippet to load the config file (only once) and access the config map:
(use 'clojure.java.io) (def config (delay (load-file (.getFile (resource "config.clj"))))) (defn get-config [] @(force config)) Now you can use get-config function to access the config map.
5 Comments
Lee
How does the app know which environment is running to load the correct settings?
Ankur
You run the app with a specific profile :
lein with-profile dev runLee
And when you deploy to somewhere like Heroku and you can't use lein with-profile (I think, but I have 5 days of after hours Clojure under my belt...). Also, can you set defaults such as run uses "dev" and your tests use "test" unless specified elsewhere?
Erin Swenson-Healey
John Doe - You can use Heroku and
lein with-profile via your Procfile, e.g. web: lein with-profile production trampoline run -m horus.core
Tommi Kyntola
I'm a little new to clojure, but the above didn't work until I removed the @. What exactly was that deref-future (?) supposed to do there?
Have a look at clj-boilerplate, a sample web app I created.
There's info in the README about how it understands environments out of the box and an example environment file can be seen here - but it looks something like this:
(def config (let [env (or (System/getenv "ENVIRONMENT") "development")] ((keyword env) {:development {:database-url "postgres://lborges:@localhost/clj-boilerplate"} :test {:database-url "postgres://lborges:@localhost/clj-boilerplate-test" :production {:database-url (System/getenv "DATABASE_URL")}}))) I have since evolved this approach but this should get you started.
Hope this helps.
Comments
Have a look at using Confijulate (plug for a personal project!):
https://github.com/bbbates/confijulate
It allows you to define environment specific configuration maps, and specify which one to use via JVM system properties.
