Sane, smart, fast, Clojure web services -- Rook

Sane, smart, fast, Clojure web services — Rook Howard Lewis
Ship - [email protected] - @hlship

Liberator (defresource entry-resource [id] :allowed-methods [:get :put :delete] :known-content-type? #(check-content-type
% ["application/json"]) :exists? (fn [_] (let [e (get @entries id)] (if-not (nil? e) {::entry e}))) :existed? (fn [_] (nil? (get @entries id ::sentinel))) :available-media-types ["application/json"] :handle-ok ::entry :delete! (fn [_] (dosync (alter entries assoc id nil))) :malformed? #(parse-json % ::data) :can-put-to-missing? false :put! #(dosync (alter entries assoc id (::data %))) :new? (fn [_] (nil? (get @entries id ::sentinel))))

Resource vs. Endpoints

Rook — Goals & Philosophy

Goal: Simple Functions

(ns org.example.resources.health-check)    (defn ping  {:route [:get []]}  []  {:status
200  :headers {}  :body "Health check A-OK!"})

(ns org.example.server (:require [ring.adapter.jetty :as jetty] [io.aviso.rook :as rook])) (defn
start-server [port] (let [handler (-> (rook/namespace-handler ['org.example.resources.health-check]) rook/wrap-with-standard-middleware)] (jetty/run-jetty handler {:port port :join? false})))

$ http localhost:8080 HTTP/1.1 200 OK Content-Length: 18 Date: Thu,
26 Mar 2015 23:49:54 GMT Server: Jetty(7.6.13.v20130916) Health check A-OK!

Goal:  Simple/Smart Access to Request Data

(ns org.example.resources.health-check)    (defn ping  {:route [:get [:id]]}  [request id] 
{:status 200  :headers {}  :body {:uri (:uri request)  :message (format "Health check %s A-OK!" id)}})  

$ http localhost:8080 HTTP/1.1 404 Not Found Cache-Control: must-revalidate,no-cache,no-store Content-Length:
1267 Content-Type: text/html;charset=ISO-8859-1 Date: Thu, 26 Mar 2015 23:59:19 GMT Server: Jetty(7.6.13.v20130916) <html> <head> <meta http-equiv="Content-Type" content="text/html;charset=ISO-8859-1"/> <title>Error 404 Not Found</title> </head> <body> <h2>HTTP ERROR: 404</h2> <p>Problem accessing /. Reason: <pre> Not Found</pre></p> <hr /><i><small>Powered by Jetty://</small></i> </body> </html>

$ http localhost:8080/gnip HTTP/1.1 200 OK Content-Length: 51 Content-Type: application/json;
charset=utf-8 Date: Fri, 27 Mar 2015 00:00:36 GMT Server: Jetty(7.6.13.v20130916) { "message": "Health check gnip A-OK!", "uri": "/gnip" }

(ns org.example.resources.health-check)    (defn ping  {:route [:get [:id]]}  [request id] 
{:status 200  :headers {}  :body {:uri (:uri request)  :message (format "Health check %s A-OK!" id)}})  

Goal:  Free From Globals

(ns org.example.resources.offers  (:require [io.aviso.rook.utils :as utils]))    (defn show  [db-conn
id]  (utils/response {:db-conn db-conn  :id id}))

(ns org.example.complex-server  (:require  [ring.adapter.jetty :as jetty]  [io.aviso.rook :as rook]  [io.aviso.rook.server
:as server]))    (defn create-handler [database-connection]  (-> (rook/namespace-handler {:arg-resolvers {'db-conn (fn [request] database-connection)}}  ["offers" 'org.example.resources.offers]  ["users" 'org.example.resources.users])  rook/wrap-with-standard-middleware))    (defn start-server  [database-connection port]  (jetty/run-jetty (server/construct-handler {:log true :reload true} #'create-handler database-connection)  {:port port :join? false}))

$ http localhost:8080/offers/1234 HTTP/1.1 200 OK Content-Length: 44 Content-Type: application/json;
charset=utf-8 Date: Fri, 27 Mar 2015 00:21:30 GMT Server: Jetty(7.6.13.v20130916) { "db-conn": "mock-db-connection", "id": "1234" }

:as server]))    (defn create-handler [database-connection]  (-> (rook/namespace-handler {:arg-resolvers {'db-conn (fn [request] database-connection)}}  ["offers" 'org.example.resources.offers]  ["users" 'org.example.resources.users])  rook/wrap-with-standard-middleware))    (defn start-server  [database-connection port]  (jetty/run-jetty (server/construct-handler {:log true :reload true} #'create-handler database-connection)  {:port port :join? false}))

{:arg-resolvers {'db-conn (fn [request] database-connection)} Symbol to match Resolves the
argument value from the request

{:arg-resolvers {'db-conn (constantly database-connection)} Symbol to match Resolves the argument
value from the request

:as server]))    (defn create-handler [database-connection]  (-> (rook/namespace-handler {:arg-resolvers {'db-conn (fn [request] database-connection)}}  ["offers" 'org.example.resources.offers]  ["users" 'org.example.resources.users])  rook/wrap-with-standard-middleware))    (defn start-server  [database-connection port]  (jetty/run-jetty (server/construct-handler {:log true :reload true} #'create-handler database-connection)  {:port port :join? false})) Development mode: the handler is recreated on each request

Goal: Leverage Metadata

(defn ping  {:route [:get [:id]]}  [request id]  {:status 200  :headers
{}  :body (format "Health check %s A-OK!" id)}) 

(defn create  {:schema create-schema  :responses create-responses  :required-permissions "auth/user/create"  :operation-trace "Creating
new user."}  […] …)

Endpoint Middleware (fn [handler endpoint-metadata]) ➠ handler Meta-data of function
merged w/ namespace metadata (to provide defaults)

(rook/compose-middleware  tracking/wrap-with-operation-tracking  (rv/wrap-with-response-validation (not production-mode))  sv/wrap-with-schema-validation  auth/auth-middleware  wrap-with-endpoint-identifier)

(defn wrap-with-operation-tracking  "Checks for the :operation-trace metadata …"  [handler metadata] 
(when-let [label (:operation-trace metadata)]  (let [logger (-> metadata :ns t/get-logger)]  (fn [request]  (t/track* logger label (handler request))))))

Middleware Shootout Ring Rook No Metadata Available Has full metadata
of endpoint function Must return a handler Can return handler, or return nil Interceptors execute during request dispatch Interceptors execute after dispatch (once endpoint known) Tree of contexts & interceptors Stack of interceptors unique for each endpoint

Goal: Efﬁcient

Checklist • Sane? — Yes, natural mapping from URIs to
simple functions • Smart? — Yes, metadata on functions w/ argument resolvers and middleware keeps code tight & free of globals • Fast? — Yes, efﬁcient dispatch & interceptors

Links • Rook — http://github.com/AvisoNovate/rook

Sane, smart, fast, Clojure web services -- Rook

Sane, smart, fast, Clojure web services -- Rook

Howard M. Lewis Ship

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