In Coast, configuration in the dev environment can come from four places, a .env file, a env.edn file, a db.edn and the OS's environment variables.

All of these files are located in the project's root directory.

You can access configuration values via the coast/env function:

(ns your-project
  (:require [coast]))

(coast/env :session-key)

Environment variable values are fetched using coast/env which accepts a keyword argument referencing the key you want in the lowercase and kebab case style. Whereas OS environment variables tend to look like this:

COAST_ENV=dev SESSION_KEY=asecret123

Coast env keys look like this:

{:coast-env "dev"
 :session-key "asecret123"}

In development, the env.edn file stores environment variables intended to be shared amongst developers, and by default this is checked in to source control. So be careful what you put in there


In production, while the code looks the same (coast/env :session-key) where the values come from should not re-use the same values that are checked into source code in env.edn.

Coast encourages the use of either an on-server .env file located at the root of the project (i.e. the same directory as the running uberjar) or set the environment variables at the OS level or when running the uberjar from the shell session like so:

COAST_ENV=prod SESSION_KEY=prodsecret123 java -jar your-app-standalone.jar

Or if you use something like supervisor, you can set the environment variables in the specific .conf file for your project:

command=java -Dclojure.server.repl="{:port 5555 :accept clojure.core.server/repl}" -Xmx100m -jar /home/deploy/your-app/your-app.jar

Common Coast env variables and their defaults:

{:coast-env "dev" ; default
 :session-key "" ; there is no default, this is required for the cookie sessions
 :port "1337" ; this is the default, set it to any port your computer is listening for connections on


All database configuration values are stored in db.edn which is also safe to check in to source control and is not .gitignore'd by default.

Here is what the default db.edn file looks like:

{:dev {:database "your_app.sqlite3"
       :adapter "sqlite"}

 :test {:database "your_app.sqlite3"
        :adapter "sqlite"}

 :prod {:database #env :db-name
        :adapter "sqlite"}}

 ; or you can use postgres

 ; :prod {:database #env :db-name
 ;        :adapter "postgres"
 ;        :username #env :db-username
 ;        :password #env :db-password
 ;        :host #env :db-host
 ;        :port #env :db-port}}

There are three different values for the three different environments the database will be running in, dev, test and prod. The prod environment is special because it uses a tagged literal and retrieves the configuration values from the environment, either .env, env.edn or the OS.

This file can and should be checked in but try not to set the production values directly in the file, instead on the production server set these environment variables:

DB_NAME=<your database name>
DB_USERNAME=<if your database is password protected>
DB_PASSWORD=<if your database is password protected>
DB_HOST=<typically localhost>
DB_PORT=<by default for postgres this is 5432>