第13课：Spark Streaming源码解读之Driver容错安全性

第13课：Spark Streaming源码解读之Driver容错安全性

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1、数据层面：ReceivedBlockTracker 是专门负责管理Spark Streaming运行的元数据。跟踪数据需维持状态。

2、调度层面：DStream和JobGenerator  框架调度的层面，从业务角度考虑的。
JobGenerator（作业生成，进展到什么地步了）。

ReceivedBlockTracker 注释写的好精彩!藏龙卧虎之地

/**
 * Class that keep track of all the received blocks, and allocate them to batches
 * when required. All actions taken by this class can be saved to a write ahead log
 * (if a checkpoint directory has been provided), so that the state of the tracker
 * (received blocks and block-to-batch allocations) can be recovered after driver failure.
 *
 * Note that when any instance of this class is created with a checkpoint directory,
 * it will try reading events f