Start and stop services in a particular order.
Based on ideas from component. Differences from component:
- No need to explicitly define dependencies for a particular service. Simply order the services in the system map to facilitate dependency needs.
- Configuration is first-class. To start the system or a particular service, a config value must be passed. This allows you to start/stop a system using a development or production config in a functional way.
- Systems can be combined and added to after inital creation.
[com.2tothe8th/system "0.2.0"]http://dubiousdavid.github.io/system/
Example scenario:
(use 'system.core)
(defrecord LDAP [conn]
Service
(start [this config deps]
(->LDAP (ldap/connect (:ldap config))))
(stop [this config]
(->LDAP (ldap/close conn))))
(defrecord MySQL [conn]
Service
(start [this config deps]
(->MySQL (mysql/connect (:mysql config))))
(stop [this config]
(->MySQL (mysql/close conn))))
(defrecord HTTP [server]
Service
(start [this config deps]
(let [routes (mk-routes (:ldap deps) (:mysql deps))]
(->HTTP (http/start (:http config) routes))))
(stop [this _]
(->HTTP (http/stop server))))
(defsystem system
:ldap (->LDAP nil)
:mysql (->MySQL nil)
:http (->HTTP nil))
(def config
{:ldap {:host "localhost" :port 389}
:mysql {:host "localhost" :port 3306}
:http {:port 80}})
;; Start the system
(def started (start system config))
;; Transform the system into a hash map
(->map started)
;; Stop the system
(stop started)You can also use conj and concat with a system to add another service or combine multiple systems.
(defsystem sys1
:ldap (->LDAP nil))
(defsystem sys2
:mysql (->MySQL nil))
;; Concatenate sys1 and sys2
(def sys3 (->SystemMap (concat sys1 sys2)))
;; Append the http service to sys1
(def sys4 (conj sys1 [:http (->HTTP nil)])
;; View the services in the order that they will be started
(pairs sys4)