storm事件管理器EventManager源码分析-event.clj
storm事件管理器定义在event.clj中，主要功能就是通过独立线程执行"事件处理函数"。我们可以将"事件处理函数"添加到EventManager的阻塞队列中，EventManager的事件处理线程不断地从阻塞队列中获取"事件处理函数"并执行。
EventManager协议
协议就是一组函数定义的集合，协议中函数的第一个参数必须为实现该协议的实例本身，类似于java中实例方法的第一个参数为this；协议类似于java中的接口。
(defprotocol EventManager
(add [this event-fn])
(waiting? [this])
(shutdown [this]))
(add [this event-fn])
(waiting? [this])
(shutdown [this]))
event-manager函数
(defn event-manager
"Creates a thread to respond to events. Any error will cause process to halt"
;; daemon?表示是否将事件处理线程设置成守护线程
[daemon?]
;; added表示已添加的"事件处理函数"的个数
(let [added (atom 0)
;; processed表示已处理的"事件处理函数"的个数
processed (atom 0)
;; queue绑定事件管理器的阻塞队列LinkedBlockingQueue
^LinkedBlockingQueue queue (LinkedBlockingQueue.)
;; 设置事件管理器的状态为"running"
running (atom true)
;; 创建事件处理线程。Clojure函数实现了Runnable和Callable接口，所以可以将Clojure函数作为参数传递给java.lang.Thread类的构造函数
runner (Thread.
;; 事件处理线程循环检查事件处理器的状态是否是"running"，如果是，就从阻塞队列中获取"事件处理函数"，并执行；然后将processed加1
(fn []
(try-cause
(while @running
(let [r (.take queue)]
(r)
(swap! processed inc)))
(catch InterruptedException t
(log-message "Event manager interrupted"))
(catch Throwable t
(log-error t "Error when processing event")
(exit-process! 20 "Error when processing an event")))))]
(.setDaemon runner daemon?)
;; 启动事件处理线程
(.start runner)
;; 返回一个实现了EventManager协议的实例
(reify
EventManager
;; add函数将"事件处理函数"添加到事件处理器的阻塞队列中
(add
[this event-fn]
;; should keep track of total added and processed to know if this is finished yet
(when-not @running
(throw (RuntimeException. "Cannot add events to a shutdown event manager")))
(swap! added inc)
(.put queue event-fn))
;; waiting?判断事件处理线程是否处于等待状态
(waiting?
[this]
(or (Time/isThreadWaiting runner)
(= @processed @added)))
;; 关闭事件管理器
(shutdown
[this]
(reset! running false)
(.interrupt runner)
(.join runner)))))
"Creates a thread to respond to events. Any error will cause process to halt"
;; daemon?表示是否将事件处理线程设置成守护线程
[daemon?]
;; added表示已添加的"事件处理函数"的个数
(let [added (atom 0)
;; processed表示已处理的"事件处理函数"的个数
processed (atom 0)
;; queue绑定事件管理器的阻塞队列LinkedBlockingQueue
^LinkedBlockingQueue queue (LinkedBlockingQueue.)
;; 设置事件管理器的状态为"running"
running (atom true)
;; 创建事件处理线程。Clojure函数实现了Runnable和Callable接口，所以可以将Clojure函数作为参数传递给java.lang.Thread类的构造函数
runner (Thread.
;; 事件处理线程循环检查事件处理器的状态是否是"running"，如果是，就从阻塞队列中获取"事件处理函数"，并执行；然后将processed加1
(fn []
(try-cause
(while @running
(let [r (.take queue)]
(r)
(swap! processed inc)))
(catch InterruptedException t
(log-message "Event manager interrupted"))
(catch Throwable t
(log-error t "Error when processing event")
(exit-process! 20 "Error when processing an event")))))]
(.setDaemon runner daemon?)
;; 启动事件处理线程
(.start runner)
;; 返回一个实现了EventManager协议的实例
(reify
EventManager
;; add函数将"事件处理函数"添加到事件处理器的阻塞队列中
(add
[this event-fn]
;; should keep track of total added and processed to know if this is finished yet
(when-not @running
(throw (RuntimeException. "Cannot add events to a shutdown event manager")))
(swap! added inc)
(.put queue event-fn))
;; waiting?判断事件处理线程是否处于等待状态
(waiting?
[this]
(or (Time/isThreadWaiting runner)
(= @processed @added)))
;; 关闭事件管理器
(shutdown
[this]
(reset! running false)
(.interrupt runner)
(.join runner)))))
