Simple restart approach

Use a def expression to create a named reference to the running server, providing a simple way to stop the application server.

The app-server starts when the application starts, as the app-server-start is called from -main once the port value has been taken from either an argument to -main, an operating system $PORT environment variable or the default 8080.

(def app-server-instance (-main 8080)) is placed within a (comment ) expression. This provides a manual way for the developer to start the application server.

The app-server-instance is a symbol pointing to the server instance. This instance can be used to shut down the server.

When the developer evaluates (.stop app-server-instance), the instance is used to shut down the running application server.

The REPL itself is still running, so the application can be started again quickly by evaluating (def app-server-instance (-main 8888)).

Code Example

(ns practicalli.example-webapp
  (:gen-class)
  (:require [ring.adapter.jetty :as jetty]
            [compojure.core :refer [defroutes GET]]))


;; Routing

(defroutes app
  (GET "/" [] {:status 200 :body "App Server Running"}))


;; System

  (defn app-server-start
    [port]
    (jetty/run-jetty (site #'app) {:port port :join? false}))


  (defn -main [& [port]]
    (let [port (Integer. (or port
                             (System/getenv "PORT")
                             8888))]
      (app-server-start port)))


;; REPL driven development

(comment

  (def app-server-instance (-main 8888))
  (.stop app-server-instance)
)

The -main function identifies a value for a port and calls app-server-start function which starts the http-kit server.

(def app-server-instance (-main 8888)) is placed within a (comment ) expression. This provides a manual way for the developer to start the application server.

The app-server-instance reference can be used to stop the app-server by calling it with the arguments :timeout 100 and gracefully shutting down the server, (app-server-instance :timeout 100).

Code Example

(ns practicalli.example-webapp
  (:gen-class)
  (:require [org.httpkit.server :as app-server]
            [compojure.core :refer [defroutes GET]]))


;; Routing

(defroutes app
  (GET "/" [] {:status 200 :body "App Server Running"}))


;; System

(defn app-server-start
  "Start the application server and run the application"
  [port]
  (println "INFO: Starting server on port: " port)
  (app-server/run-server #'app {:port port}))

(defn -main
  "Start the application server on a speicific port"
  [& [port]]
  (let [port (Integer. (or port (System/getenv "PORT") 8888))]
    (app-server-start port)))


;; REPL driven develpment

(comment

  (def app-server-instance (-main 8888))
  (app-server-instance :timeout 100)
)

Http-kit server documentation contains details of asynchronous websockets and HTTP streaming configurations.

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