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Integrant Config

A global configuration to start, restart and halt all the services that make up the system.

{:practicalli.scoreboard.service/app-server
 {:handler #ig/ref :practicalli.scoreboard.service/router
  :port 8888
  :join? false}

 :practicalli.scoreboard.service/router
 {:persistence-connection #ig/ref :practicalli.scoreboard.service/persistence}

 :practicalli.scoreboard.service/persistence
 {:connection {:url "http://localhost/" :port 12345 :database "scoreboard"}}
 #_()}

aero configuration for multiple environments

{:practicalli.scoreboard.service/app-server
 {:handler #ig/ref :practicalli.scoreboard.service/router
  :port #profile {:develop #long #or [#env APP_SERVER_PORT 8888]
                  :stage   #long #or [#env APP_SERVER_PORT 8080]
                  :live    #long #or [#env APP_SERVER_PORT 8000]}
  :join? false}

 :practicalli.scoreboard.service/router
 {:persistence #ig/ref :practicalli.scoreboard.service/relational-data-store}

 :practicalli.scoreboard.service/relational-data-store
 {:connection #profile {:develop  {:url "http://localhost/" :port 57207 :database "customer-entitlements-develop"}
                        :stage    {:url "http://localhost/" :port 57207 :database "customer-entitlements-stage"}
                        :live     {:url "http://localhost/" :port 57207 :database "customer-entitlements"}}
  ;;TODO: dynamodb: provide environment variables / access credentials for all environments
  }
 #_()}

configuration: environment profiles with aero

Aero library provides tag literals to configure values specific to each environment, all from one configuration file

Tag literals include

  • #profile - define a map of environment values
  • #env - get values from environment variables
  • #or - first truthy value from a vector of options
  • #long - cast a value to a Clojure long type

Configuration file - config.edn

Renamed top-level keys to represent namespace each key is initiated in and use auto-resolve names for the ig/init-key defmethod expressions

Start / Stop service

Use aero to prepare the configuration and start & stop helper functions to easily manage the application from the REPL

Dependencies

  • remove environ
  • add aero

Integrant pitfalls

Avoid using the same name for a key inside a configuration as the name for a referred (top-level) key

In this example the :persistence key clashes with the :practicalli.scoreboard.service/persistence top-level key

 :practicalli.scoreboard.service/router
 {:persistence #ig/ref :practicalli.scoreboard.service/key-value-store}

 :practicalli.scoreboard.service/key-value-store
 {:connection #profile {:develop  {:url "http://localhost/" :port 57207 :database "customer-entitlements-develop"}
                        :stage    {:url "http://localhost/" :port 57207 :database "customer-entitlements-stage"}
                        :live     {:url "http://localhost/" :port 57207 :database "customer-entitlements"}}

Integrant REPL

Example

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Development tools namespace
;;
;; Rich comment block contains expressions to start, restart and halt the system
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(ns user
 "Development tools to manage component lifecycle"
  (:require
   [aero.core            :as aero]
   [clojure.java.io      :as io]
   [integrant.repl       :as ig-repl]
   [integrant.repl.state :as ig-state]

   [clojure.pprint :as pprint]))


;;;; System Configuration

(defn environment-prep!
  "Parse system configuration with aero-reader and apply the given profile values
  Return: Integrant configuration to be used to start the system"
  [profile]
  (aero/read-config (io/resource "config.edn") {:profile profile})
  #_(ig-repl/set-prep! (practicalli.entitlements.service/aero-prep :develop)))


;;;; REPL convenience functions

(defn go
  "Prepare configuration and start the system services with Integrant-repl"
  ([] (go :develop))
  ([profile] (environment-prep! profile) (ig-repl/go)))


(defn reset
  "Read updates from the configuration and restart the system services with Integrant-repl"
  [profile] (environment-prep! profile) (ig-repl/reset))

(defn halt
  "Shutdown all services"
  [] (ig-repl/halt))

(defn system
  "The running system configuration"
  [] (ig-state/system))

(defn config
  "The current system configuration used by Integrant"
  [] (ig-state/config))


;; Rich comment block with redefined vars ignored
#_{:clj-kondo/ignore [:redefined-var]}
(comment

  ;; Prepare and start the system using the :develop profile
  (go)

  ;; Reload source files and restart the system:
  (reset :develop)

  ;; Return the Integrant configuration
  (config)

  ;; Shutdown the system using the app-server object reference in the Integrant state
  (halt)

  ;; Show the running system configuration
  (system)

  ;; Print the system state in the REPL
  (pprint/pprint ig-state/system)

  #_()) ;; End of rich comment block

Return the integrant configuration from the configuration file

#_(ig-repl/set-prep! (fn [] (-> "resources/config.edn" slurp ig/read-string)))

System Configuration

(defn environment-prep!
  "Parse system configuration with aero-reader and apply the given profile values
  Return: Integrant configuration to be used to start the system"
  [profile]
  (aero/read-config (io/resource "config.edn") {:profile profile})
  #_(ig-repl/set-prep! (practicalli.entitlements.service/aero-prep :develop)))

Define go as a REPL convenience function, optionally taking a keyword representing the name of environment to run under

(defn go
  "Prepare configuration and start the system services with Integrant-repl"
  ([] (go :develop))
  ([profile] (environment-prep! profile) (ig-repl/go)))

Rather than using a arity based polymorphic function, use the & variable arity syntax and use or to use the argument or :dev profile

(defn go-redux
  "Prepare configuration and start the system services with Integrant-repl"
  [& profile]
  (set-prep! (or (first profile) :develop))
  (ig-repl/go))

Set directories monitored for changed files:

(require '[clojure.tools.namespace.repl :refer [set-refresh-dirs]])
(set-refresh-dirs "src")