Spark application注册master机制

直接上Master类的代码：

 case RegisterApplication(description) => {
      if (state == RecoveryState.STANDBY) {
        // ignore, don't send response
      } else {
        logInfo("Registering app " + description.name)
        val app = createApplication(description, sender)
        registerApplication(app)
        logInfo("Registered app " + description.name + " with ID " + app.id)
        persistenceEngine.addApplication(app)
        sender ! RegisteredApplication(app.id, masterUrl)
        schedule()
      }
    }

代码很直白-》

1：如果是（standby）备用master节点的话那么SparkDeploySchedulerBakend注册过来后什么都不做！

2：如果是active master的话就会根据standalone启动jar包时配置的参数（传递过来后被封装成ApplicationDescription对象），映射到ApplicationInfo中，并添加到app集合中；

3：sender ! RegisteredApplication(app.id, masterUrl)就是多个Actor之间的通信机制，相当于SparkDeploySchedulerBakend注册到master后的反注册动作；