当调用launch-worker的时候, clojure会自动根据defmulti里面定义的fn来判断是调用哪个版本的launch-worker
(defmulti launch-worker (fn [supervisor & _] (cluster-mode (:conf supervisor))))
(defmethod launch-worker :distributed [supervisor storm-id port worker-id] (let [conf (:conf supervisor) storm-home (System/getProperty "storm.home") stormroot (supervisor-stormdist-root conf storm-id) stormjar (supervisor-stormjar-path stormroot) storm-conf (read-supervisor-storm-conf conf storm-id) classpath (add-to-classpath (current-classpath) [stormjar]) childopts (.replaceAll (str (conf WORKER-CHILDOPTS) " " (storm-conf TOPOLOGY-WORKER-CHILDOPTS)) "%ID%" (str port)) logfilename (str "worker-" port ".log") command (str "java -server " childopts " -Djava.library.path=" (conf JAVA-LIBRARY-PATH) " -Dlogfile.name=" logfilename " -Dstorm.home=" storm-home " -Dlogback.configurationFile=" storm-home "/logback/cluster.xml" " -cp " classpath " backtype.storm.daemon.worker " (java.net.URLEncoder/encode storm-id) " " (:assignment-id supervisor) " " port " " worker-id)] (log-message "Launching worker with command: " command) (launch-process command :environment {"LD_LIBRARY_PATH" (conf JAVA-LIBRARY-PATH)}) )) (defmethod launch-worker :local [supervisor storm-id port worker-id] (let [conf (:conf supervisor) pid (uuid) worker (worker/mk-worker conf (:shared-context supervisor) storm-id (:assignment-id supervisor) port worker-id)] (psim/register-process pid worker) (swap! (:worker-thread-pids-atom supervisor) assoc worker-id pid) ))
在executor.clj中通过multimethods来区分blot和spout不同的创建逻辑
(defmulti mk-threads executor-selector) (defmulti mk-executor-stats executor-selector) (defmulti close-component executor-selector) 本文章摘自博客园，原文发布日期：2013-06-28 相关资源：敏捷开发V1.0.pptx