Storm-源码分析- hook (backtype.storm.hooks)-白红宇

task hook

在某些task事件发生时, 如果用户希望执行一些额外的逻辑, 就需要使用hook

当前定义如下事件, emit, cleanup, spoutAck……

用户只需要开发实现ITaskHook的类, 并将类名配置到(storm-conf TOPOLOGY-AUTO-TASK-HOOKS)

系统会在这些事件发生时, 自动调用所有注册的hook中的相应的functions

public interface ITaskHook {    void prepare(Map conf, TopologyContext context);    void cleanup();    void emit(EmitInfo info);    void spoutAck(SpoutAckInfo info);    void spoutFail(SpoutFailInfo info);    void boltExecute(BoltExecuteInfo info);    void boltAck(BoltAckInfo info);    void boltFail(BoltFailInfo info);}

public class EmitInfo {    public List

1. add hook

在mk-task的时候, 会从storm-conf配置里面读出hooks的class names

创建hook对象, 加入到TopologyContext的_hooks中

(defn mk-task [executor-data task-id]    (doseq [klass (storm-conf TOPOLOGY-AUTO-TASK-HOOKS)]      (.addTaskHook ^TopologyContext (:user-context task-data) (-> klass Class/forName .newInstance))))

public class TopologyContext extends WorkerTopologyContext implements IMetricsContext {    private List
     
       _hooks = new ArrayList
      
       ();        public void addTaskHook(ITaskHook hook) {        hook.prepare(_stormConf, this);        _hooks.add(hook);    }        public Collection
       
         getHooks() {        return _hooks;    }}

2. apply hook

当发生相应的事件时, 调用事先注册的hooks

下面的例子是在emit时, 调用相应的hooks

apply-hooks宏实现也很简单, 从topology context中取出hooks列表, 对每个hook调用emit(EmitInfo)

(apply-hooks user-context .emit (EmitInfo. values stream task-id out-tasks))

(defmacro apply-hooks [topology-context method-sym info-form]  (let [hook-sym (with-meta (gensym "hook") {:tag 'backtype.storm.hooks.ITaskHook})]    `(let [hooks# (get-context-hooks ~topology-context)]       (when-not (hooks-empty? hooks#)         (let [info# ~info-form]           (fast-list-iter [~hook-sym hooks#]             (~method-sym ~hook-sym info#)             ))))))

本文章摘自博客园，原文发布日期：2013-07-30