This document discusses how to build a reloadable Clojure application using Stuart Sierra's Component framework. It describes setting up the application with different components like a database connection, services, and a web server. Components are assembled into a system map and can be started, stopped, and reloaded altogether or individually via the REPL. The components close over dependencies injected by the system so changes can take effect on reload.

1. Reloadable ClojureApp
Stuart Sierra's Component Framework

2. » Signifier
» 93-00
» 01-16 ・通信系スタートアップで開
発
» 16 7 Signifier Clojure
» Clojure

3. Clojure
» REPL
»
» ->Prismatic Schema

4. REPL
» pallet/alembic ... (load-project)
» user=> (use 'my-ns.a-namespace :reload)
» :reload
»
» defmulti/defprotocol/macro
» Closure

5. clojure/tools.namespace
user=> (require '[clojure.tools.namespace.repl :refer [refresh]])
nil
user=> (refresh)
:reloading (com.example.util com.example.app com.example.app-test)
:ok

6. clojure/tools.namespace
» ring.middleware.reload
(ns myapp
(:require
[compojure.core :refer [GET defroutes]]
[ring.middleware.reload :refer [wrap-reload]]))
(defroutes app
(GET "/" [] "hello world"))
(def reloadable-app
(wrap-reload app))
» reload >> weavejester/ns-tracker >> clojure/tools.namespace

7. c.t.namespace
»
» def ・シングルトン
(def state-of-world (ref {}))
(def object-handle (atom nil))

8. c.t.namespace
»
(defn create-application []
{:state-of-world (ref {})
:object-handle (atom nil)})
def DB connection,
config, etc...

9. ...
» Stuart Sierra's Component
» Record/Map
・終了処理を管理する
» API
»
» Map (System)
»

10. » danielsz/system
»
» Jetty, HTTP kit, Carmine, ElasticSearch, etc...
» (e.g. Jetty)
» API

11. project.clj
(defproject a-project-ec "0.1.0-SNAPSHOT"
(...snip...)
:dependencies
[[funcool/clojure.jdbc "0.9.0"]
[hikari-cp "1.7.4"]
[honeysql "0.8.0"]
[http-kit "2.1.18"]
[metosin/compojure-api "1.1.7" :exclusions [org.clojure/tools.reader]]
[migratus "0.8.31"]
[org.clojure/clojure "1.8.0"]
[org.danielsz/system "0.3.1"]
[org.postgresql/postgresql "9.4.1211"]
[ring "1.5.0" :exclusions [commons-codec
org.clojure/tools.reader]]]
(...snip...)

12. user.clj
(ns user
(:require
[system.repl :as repl :refer [system set-init! start stop reset]]
[clojure.tools.namespace.repl :refer [refresh]]
[a-project-ec.systems :refer [dev-system]]))
(set-init! #'dev-system)
(defn reload []
(stop)
(refresh :after 'system.repl/reset))

13. systems.clj
(ns a-project-ec.systems
(:require [com.stuartsierra.component :as component]
[a-project-ec.components.customer-master :refer [new-customer-master]]
[a-project-ec.components.jetty :refer [new-web-server]]
[a-project-ec.components.migratus :refer [new-migratus]]
[a-project-ec.components.orders :refer [new-orders]]
[a-project-ec.components.product-master :refer [new-product-master]]
[a-project-ec.components.ring-handler :refer [new-ring-handler]]
[system.components.hikari :refer [new-hikari-cp]]
[system.components.repl-server :refer [new-repl-server]]
[system.core :refer [defsystem]]))

14. systems.clj
(defn dev-system []
(component/system-map
:customer-master (new-customer-master)
:hikari-cp (component/using
(new-hikari-cp {:adapter "postgresql"
:username "a-project"
:password "password"
:database-name "a-project"
:server-name "localhost"
:port-number 5432})
[:migratus])
:migratus (new-migratus {:store :database
:migration-dir "migrations"
:db {:classname "org.postgresql.ds.PGSimpleDataSource"
:subprotocol "postgresql"
:subname "//localhost:5432/a-project"
:user "a-project"
:password "a-project123"}})
:orders (component/using
(new-orders)
[:hikari-cp :product-master :customer-master])
:product-master (new-product-master)
:ring-handler (component/using
(new-ring-handler) [:customer-master
:orders
:product-master])
:web (component/using
(new-web-server (Integer. (or (env :http-port) "3000")))
{:handler :ring-handler})))
(defn prod-system []
(dev-system))

15. systems.clj
» component/system-map Component SystemMap
» component/using Map/Record Vector
Inject
(component/system-map
:customer-master (new-customer-master)
:hikari-cp (component/using
(new-hikari-cp {:adapter "postgresql"
:username "a-project"
:password "password"
:database-name "a-project"
:server-name "localhost"
:port-number 5432})
[:migratus])
:migratus (new-migratus {:store :database
:migration-dir "migrations"
...

16. System
» System
user=>(start)
»
user=>(stop)
»
user=>(reload)

17. product-master.clj
(ns a-project-ec.components.product-master
(:require [again.core :as again]
[cheshire.core :as json]
[com.stuartsierra.component :as component]
[a-project-ec.retry :as retry]
[org.httpkit.client :as http]
[schema.core :as s]
[slingshot.slingshot :refer [throw+]]
[taoensso.timbre :as log]))

18. product-master.clj
(def sheetsu-api-url "https://sheetsu.com/apis/v1.0/123456abcde")
(def sheetsu-basic-auth-user "a-user")
(def sheetsu-basic-auth-pass "a-password")
(defn load-product-master
[product-master]
(again/with-retries
retry/http-call-intervals
(let [options {:basic-auth [sheetsu-basic-auth-user
sheetsu-basic-auth-pass]}
{:keys [status
headers
body
error] :as resp} @(http/get sheetsu-api-url options)]
(if (or (nil? status) (>= status 300))
(do (log/warn "load-product-master: failed to call sheetsu api." error)
(throw+ {:type :rest-api-failure :message error :status status}))
(reset! product-master (json/parse-string body true)))))
product-master)

19. product-master.clj
(defrecord ProductMaster [product-master]
component/Lifecycle
(start [component]
(log/info "Starting ProductMaster...")
(assoc component :product-master (load-product-master product-master)))
(stop [component]
(log/info "Stopping ProductMaster...")
(dissoc component :product-master)))
(defn new-product-master
[]
(map->ProductMaster {:product-master (atom nil)}))

20. def ...
(defn load-product-master
[product-master sheetsu-api-url
sheetsu-basic-auth-user sheetwsu-basic-auth-pass]
(again/with-retries
retry/http-call-intervals
(let [options {:basic-auth [sheetsu-basic-auth-user
sheetsu-basic-auth-pass]}
{:keys [status
headers
body
error] :as resp} @(http/get sheetsu-api-url options)]
(if (or (nil? status) (>= status 300))
(do (log/warn "load-product-master: failed to call sheetsu api." error)
(throw+ {:type :rest-api-failure :message error :status status}))
(reset! product-master (json/parse-string body true)))))
product-master)
(defrecord ProductMaster [product-master]
component/Lifecycle
(start [component]
(log/info "Starting ProductMaster...")
(assoc component :product-master (load-product-master product-master)))
(stop [component]
(log/info "Stopping ProductMaster...")
(dissoc component :product-master)))
(defn new-product-master
[url user pass]
(map->ProductMaster {:sheetsu-api-url url
:sheetsu-basic-auth-user user
:sheetsu-basic-auth-pass pass
:product-master (atom nil)}))

21. systems.clj config
:product-master (new-product-master "https://sheetsu.com/apis/v1.0/123456abcde"
"a-user" "a-pass")

22. Injection hikari-cp-> orders
(ns a-project-ec.systems
(:require ...
[system.components.hikari :refer [new-hikari-cp]]))
:hikari-cp (component/using
(new-hikari-cp {:adapter "postgresql"
:username "a-project"
:password "password"
:database-name "a-project"
:server-name "localhost"
:port-number 5432})
[:migratus])
:orders (component/using
(new-orders)
[:hikari-cp :product-master :customer-master])

23. Injection orders.clj
(ns a-project-ec.components.orders
(:require [clj-uuid :as uuid]
[com.stuartsierra.component :as component]
[a-project-ec.crud :as crud]
[a-project-ec.schema.a-project :refer :all]
[jdbc.core :as jdbc]
[schema.core :as s]
[taoensso.timbre :as log]))

24. Injection orders.clj
(def salt "12345668-abcd-1111-2222-1a2b3c4d5e6f")
(defrecord Orders [hikari-cp product-master customer-master])
(defn new-orders []
(map->Orders {}))

25. Injection orders.clj
(s/defn order-item-id :- s/Uuid
[order-id :- s/Uuid
product-code :- ProductCode]
(uuid/v5 order-id product-code))
(s/defn create :- s/Uuid
[this :- Orders
order :- OrderRequest]
(log/info "order-req:" order)
(let [{:keys [hikari-cp product-master customer-master]} this
order-id (-> (uuid/v1)
(uuid/v5 salt)
(uuid/v5 (:retailer-id order)))
order (-> order
(assoc :id order-id)
(assoc :order-items (map #(assoc %
:id (order-item-id order-id (:product-code %))
:order-id order-id)
(:order-items order))))]
(jdbc/atomic hikari-cp
(let [id (crud/create hikari-cp :orders (dissoc order :order-items))]
(for [order-item (:order-items order)]
(crud/create hikari-cp :order-items order-item))
id))))

26. Injection crud.clj
(s/defn create :- s/Str
[conn
table :- s/Keyword
kv :- {s/Keyword s/Any}]
(let [kv (assoc kv
:created-at :%now
:updated-at :%now)
sql (-> (h/insert-into table)
(h/values [kv])
(ph/returning :id)
sql/format)]
(log/debug "create:" sql)
(:id (first (jdbc/fetch conn sql)))))

27. Close over
» systems.clj
:ring-handler (component/using
(new-ring-handler) [:customer-master
:orders
:product-master])
» ring-handler.clj
(ns a-project-ec.components.ring-handler
(:require [com.stuartsierra.component :as component]
[compojure.api.sweet :refer :all]
[a-project-ec.routes.customer-master :refer [customer-master-routes]]
[a-project-ec.routes.order :refer [order-routes]]
[a-project-ec.routes.product-master :refer [product-master-routes]]
[ring.util.http-response :refer :all]
[schema.core :as s]
[taoensso.timbre :as log]))

28. Close over
(defmethod compojure.api.meta/restructure-param :components
[_ components acc]
(update-in acc [:letks] into
[components `(::components ~'+compojure-api-request+)]))
(defn wrap-components [handler components]
(fn [req]
(handler (assoc req ::components components))))
(s/defn make-handler
[this handler-fn]
(wrap-components handler-fn this))

29. Close over
(def app
(api
{:swagger
{:ui "/a-project-ec/api-docs"
:spec "/a-project-ec/swagger.json"
:data {:basePath "/"
:info {:title "a-project E-commerce API"
:description "API for Cigar Retailers"}}}}
customer-master-routes
order-routes
product-master-routes))
(s/defrecord RingHandler [product-master]
component/Lifecycle
(start [component]
(log/info "Starting RingHandler...")
(assoc component
:handler-fn (make-handler component #'app)))
(stop [component]
(log/info "Shutting down RingHandler...")
(dissoc component :deps :handler-fn)))
(s/defn new-ring-handler
[] (map->RingHandler {}))

30. Ring-handler Jetty Inject
(ns a-project-ec.components.jetty
(:require [a-project-ec.components.ring-handler :as h]
[taoensso.timbre :as log]
[com.stuartsierra.component :as component]
[ring.adapter.jetty :refer [run-jetty]]
[schema.core :as s])
(:import (org.eclipse.jetty.server Server)))

31. Ring-handler Jetty Inject
(s/defrecord WebServer
[port :- s/Int
server :- Server
handler :- h/->RingHandler]
component/Lifecycle
(start [component]
(log/info "Starting Jetty...")
(if (nil? (:server component))
(try
(let [handler (:handler-fn handler)
server (run-jetty handler {:port port :join? false})]
(assoc component :server server))
(catch java.net.BindException e
(log/warn e "Jetty has already started.")
component))
component))
(stop [component]
(log/info "Shutting down Jetty...")
(when server
(try (.stop server)
(catch Throwable t
(log/warn t "Failed to stp Jetty.")))
(dissoc component :server))))

32. Ring-handler Jetty Inject
(defn new-web-server
([port]
(map->WebServer {:port port}))
([port handler]
(map->WebServer {:port port :handler handler})))

33. compojure-api Component
(defroutes order-routes
(context "/a-project-ec/api/orders" []
:tags ["Orders"]
(POST "/" []
:components [orders]
:return OrderId
:summary " "
:body [order-request OrderRequest]
(ok (orders/create orders order-request)))))

34. FAQ
»
» System
»
» System Inject
»
» system.repl/system (:orders
system.repl/system) Component

35. Component
» (reload) REPL
» REPL
»
» DB ring middleware
REPL
»

36. » @k2nakamura
» http://signifier.jp