这篇文章主要介绍“Driver容错安全性怎么实现”，在日常操作中，相信很多人在Driver容错安全性怎么实现问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”Driver容错安全性怎么实现”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！

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• ·  第一、看ReceiverTracker的容错，主要是ReceiverTracker接收元数据的进入WAL,看ReceiverTracker的addBlock方法，代码如下

  def addBlock(receivedBlockInfo: ReceivedBlockInfo): Boolean = {

   try {

     val writeResult = writeToLog(BlockAdditionEvent(receivedBlockInfo))

     if (writeResult) {

       synchronized {

         getReceivedBlockQueue(receivedBlockInfo.streamId) += receivedBlockInfo

       }

       logDebug(s"Stream ${receivedBlockInfo.streamId} received " +

         s"block ${receivedBlockInfo.blockStoreResult.blockId}")

     } else {

       logDebug(s"Failed to acknowledge stream ${receivedBlockInfo.streamId} receiving " +

         s"block ${receivedBlockInfo.blockStoreResult.blockId} in the Write Ahead Log.")

     }

     writeResult

   } catch {

     case NonFatal(e) =>

       logError(s"Error adding block $receivedBlockInfo", e)

       false

   }

  }

  writeToLog方法就是进行WAL的操作，看writeToLog的代码

  private def writeToLog(record: ReceivedBlockTrackerLogEvent): Boolean = {

   if (isWriteAheadLogEnabled) {

     logTrace(s"Writing record: $record")

     try {

       writeAheadLogOption.get.write(ByteBuffer.wrap(Utils.serialize(record)),

         clock.getTimeMillis())

       true

     } catch {

       case NonFatal(e) =>

         logWarning(s"Exception thrown while writing record: $record to the WriteAheadLog.", e)

         false

     }

   } else {

     true

   }

  }

  首先判断是否开启了WAL，根据一下isWriteAheadLogEnabled值

  private[streaming] def isWriteAheadLogEnabled: Boolean = writeAheadLogOption.nonEmpty

  接着看writeAheadLogOption

  private val writeAheadLogOption = createWriteAheadLog()

  再看createWriteAheadLog()方法

  private def createWriteAheadLog(): Option[WriteAheadLog] = {

   checkpointDirOption.map { checkpointDir =>

     val logDir = ReceivedBlockTracker.checkpointDirToLogDir(checkpointDirOption.get)

     WriteAheadLogUtils.createLogForDriver(conf, logDir, hadoopConf)

   }

  }

  根据checkpoint的配置，获取checkpoint的目录，这里可以看出，checkpoint可以有多个目录。
  写完WAL才将receivedBlockInfo放到内存队列getReceivedBlockQueue中

  ·  第二、看ReceivedBlockTracker的allocateBlocksToBatch方法，代码如下

  def allocateBlocksToBatch(batchTime: Time): Unit = synchronized {

   if (lastAllocatedBatchTime == null || batchTime > lastAllocatedBatchTime) {

     val streamIdToBlocks = streamIds.map { streamId =>

         (streamId, getReceivedBlockQueue(streamId).dequeueAll(x => true))

     }.toMap

     val allocatedBlocks = AllocatedBlocks(streamIdToBlocks)

     if (writeToLog(BatchAllocationEvent(batchTime, allocatedBlocks))) {

       timeToAllocatedBlocks.put(batchTime, allocatedBlocks)

       lastAllocatedBatchTime = batchTime

     } else {

       logInfo(s"Possibly processed batch $batchTime need to be processed again in WAL recovery")

     }

   } else {

     // This situation occurs when:

     // 1. WAL is ended with BatchAllocationEvent, but without BatchCleanupEvent,

     // possibly processed batch job or half-processed batch job need to be processed again,

     // so the batchTime will be equal to lastAllocatedBatchTime.

     // 2. Slow checkpointing makes recovered batch time older than WAL recovered

     // lastAllocatedBatchTime.

     // This situation will only occurs in recovery time.

     logInfo(s"Possibly processed batch $batchTime need to be processed again in WAL recovery")

   }

  }

  首先从getReceivedBlockQueue中获取每一个receiver的ReceivedBlockQueue队列赋值给streamIdToBlocks，然后包装一下

  val allocatedBlocks = AllocatedBlocks(streamIdToBlocks)

  allocatedBlocks就是根据时间获取的一批元数据，交给对应batchDuration的job，job在执行的时候就可以使用，在使用前先进行WAL，如果job出错恢复后，可以知道数据计算到什么位置

  val allocatedBlocks = AllocatedBlocks(streamIdToBlocks)

     if (writeToLog(BatchAllocationEvent(batchTime, allocatedBlocks))) {

       timeToAllocatedBlocks.put(batchTime, allocatedBlocks)

       lastAllocatedBatchTime = batchTime

     } else {

       logInfo(s"Possibly processed batch $batchTime need to be processed again in WAL recovery")

  }

  ·  第三、看cleanupOldBatches方法，cleanupOldBatches的功能是从内存中清楚不用的batches元数据，再删除WAL的数据，再删除之前把要删除的batches信息也进行WAL

  def cleanupOldBatches(cleanupThreshTime: Time, waitForCompletion: Boolean): Unit = synchronized {

   require(cleanupThreshTime.milliseconds < clock.getTimeMillis())

   val timesToCleanup = timeToAllocatedBlocks.keys.filter { _ < cleanupThreshTime }.toSeq

   logInfo("Deleting batches " + timesToCleanup)

   if (writeToLog(BatchCleanupEvent(timesToCleanup))) {

     timeToAllocatedBlocks --= timesToCleanup

     writeAheadLogOption.foreach(_.clean(cleanupThreshTime.milliseconds, waitForCompletion))

   } else {

     logWarning("Failed to acknowledge batch clean up in the Write Ahead Log.")

   }

  }

  ·  总结一下上面的三种WAL,对应下面的三种事件，这就是ReceiverTracker的容错

  /** Trait representing any event in the ReceivedBlockTracker that updates its state. */

  private[streaming] sealed trait ReceivedBlockTrackerLogEvent

  private[streaming] case class BlockAdditionEvent(receivedBlockInfo: ReceivedBlockInfo)

  extends ReceivedBlockTrackerLogEvent

  private[streaming] case class BatchAllocationEvent(time: Time, allocatedBlocks: AllocatedBlocks)

  extends ReceivedBlockTrackerLogEvent

  private[streaming] case class BatchCleanupEvent(times: Seq[Time])  extends ReceivedBlockTrackerLogEvent

  ·  看一下Dstream.graph和JobGenerator的容错，从开始

  private def generateJobs(time: Time) {

  SparkEnv has been removed.

   SparkEnv.set(ssc.env)

   Try {

   

     // allocate received blocks to batch

     // 分配接收到的数据给batch

     jobScheduler.receiverTracker.allocateBlocksToBatch(time)

     // 使用分配的块生成jobs

     graph.generateJobs(time) // generate jobs using allocated block

   } match {

     case Success(jobs) =>

       // 获取元数据信息

       val streamIdToInputInfos = jobScheduler.inputInfoTracker.getInfo(time)

       // 提交jobSet

       jobScheduler.submitJobSet(JobSet(time, jobs, streamIdToInputInfos))

     case Failure(e) =>

       jobScheduler.reportError("Error generating jobs for time " + time, e)

   }

   eventLoop.post(DoCheckpoint(time, clearCheckpointDataLater = false))

  }

  jobs生成完成后发送DoCheckpoint消息，最终调用doCheckpoint方法,代码如下

  private def doCheckpoint(time: Time, clearCheckpointDataLater: Boolean) {

   if (shouldCheckpoint && (time - graph.zeroTime).isMultipleOf(ssc.checkpointDuration)) {

     logInfo("Checkpointing graph for time " + time)

     ssc.graph.updateCheckpointData(time)

     checkpointWriter.write(new Checkpoint(ssc, time), clearCheckpointDataLater)

   }

  }

   

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