1 override def execute(triggerHandler: () => Boolean): Unit = {
 2     while (true) {
 3       val triggerTimeMs = clock.getTimeMillis
 4       val nextTriggerTimeMs = nextBatchTime(triggerTimeMs)
 5       val terminated = !triggerHandler()
 6       if (intervalMs > 0) {
 7         val batchElapsedTimeMs = clock.getTimeMillis - triggerTimeMs
 8         if (batchElapsedTimeMs > intervalMs) {
 9           notifyBatchFallingBehind(batchElapsedTimeMs)
10         }
11         if (terminated) {
12           return
13         }
14         clock.waitTillTime(nextTriggerTimeMs)
15       } else {
16         if (terminated) {
17           return
18         }
19       }
20     }
21   }

def execute(triggerHandler: () => Boolean): Unit = {
 while(true) {
    獲取current_time
    根據current_time和interval獲取下一個批次start_time
    執行query任務獲取並獲取是否結束stream的標誌位
    if(interval > 0) {
       query使用時間 = 新獲取的current_time - 舊的current_time
       if(query使用時間 > interval) {
          notifyBatchFallingBehind // 目前只是列印warn日誌
       }
       if(stream終止標誌位為true){
          return // 結束這個while循環退出方法
       }
        // Clock.waitTillTime SystemClock子類通過while + sleep(ms)實現，其餘子類通過while + wait(ms) 來實現,使用while是為了防止外部中斷導致wait時間不夠
    } else {
       if(stream終止標誌位為true){
          return // 結束這個while循環退出方法
       }
    }
 }
}

 1 override protected def runActivatedStream(sparkSessionForStream: SparkSession): Unit = {
 2     val stateUpdate = new UnaryOperator[State] {
 3       override def apply(s: State) = s match {
 4         // If we ended the query to reconfigure, reset the state to active.
 5         case RECONFIGURING => ACTIVE
 6         case _ => s
 7       }
 8     }
 9 
10     do {
11       runContinuous(sparkSessionForStream)
12     } while (state.updateAndGet(stateUpdate) == ACTIVE)
13   }

  /**
   * Do a continuous run.
   * @param sparkSessionForQuery Isolated [[SparkSession]] to run the continuous query with.
   */
  private def runContinuous(sparkSessionForQuery: SparkSession): Unit = {
    // A list of attributes that will need to be updated.
    val replacements = new ArrayBuffer[(Attribute, Attribute)]
    // Translate from continuous relation to the underlying data source.
    var nextSourceId = 0
    continuousSources = logicalPlan.collect {
      case ContinuousExecutionRelation(dataSource, extraReaderOptions, output) =>
        val metadataPath = s"$resolvedCheckpointRoot/sources/$nextSourceId"
        nextSourceId += 1

        dataSource.createContinuousReader(
          java.util.Optional.empty[StructType](),
          metadataPath,
          new DataSourceOptions(extraReaderOptions.asJava))
    }
    uniqueSources = continuousSources.distinct

    val offsets = getStartOffsets(sparkSessionForQuery)

    var insertedSourceId = 0
    val withNewSources = logicalPlan transform {
      case ContinuousExecutionRelation(source, options, output) =>
        val reader = continuousSources(insertedSourceId)
        insertedSourceId += 1
        val newOutput = reader.readSchema().toAttributes

        assert(output.size == newOutput.size,
          s"Invalid reader: ${Utils.truncatedString(output, ",")} != " +
            s"${Utils.truncatedString(newOutput, ",")}")
        replacements ++= output.zip(newOutput)

        val loggedOffset = offsets.offsets(0)
        val realOffset = loggedOffset.map(off => reader.deserializeOffset(off.json))
        reader.setStartOffset(java.util.Optional.ofNullable(realOffset.orNull))
        StreamingDataSourceV2Relation(newOutput, source, options, reader)
    }

    // Rewire the plan to use the new attributes that were returned by the source.
    val replacementMap = AttributeMap(replacements)
    val triggerLogicalPlan = withNewSources transformAllExpressions {
      case a: Attribute if replacementMap.contains(a) =>
        replacementMap(a).withMetadata(a.metadata)
      case (_: CurrentTimestamp | _: CurrentDate) =>
        throw new IllegalStateException(
          "CurrentTimestamp and CurrentDate not yet supported for continuous processing")
    }

    val writer = sink.createStreamWriter(
      s"$runId",
      triggerLogicalPlan.schema,
      outputMode,
      new DataSourceOptions(extraOptions.asJava))
    val withSink = WriteToContinuousDataSource(writer, triggerLogicalPlan)

    val reader = withSink.collect {
      case StreamingDataSourceV2Relation(_, _, _, r: ContinuousReader) => r
    }.head

    reportTimeTaken("queryPlanning") {
      lastExecution = new IncrementalExecution(
        sparkSessionForQuery,
        withSink,
        outputMode,
        checkpointFile("state"),
        runId,
        currentBatchId,
        offsetSeqMetadata)
      lastExecution.executedPlan // Force the lazy generation of execution plan
    }

    sparkSessionForQuery.sparkContext.setLocalProperty(
      StreamExecution.IS_CONTINUOUS_PROCESSING, true.toString)
    sparkSessionForQuery.sparkContext.setLocalProperty(
      ContinuousExecution.START_EPOCH_KEY, currentBatchId.toString)
    // Add another random ID on top of the run ID, to distinguish epoch coordinators across
    // reconfigurations.
    val epochCoordinatorId = s"$runId--${UUID.randomUUID}"
    currentEpochCoordinatorId = epochCoordinatorId
    sparkSessionForQuery.sparkContext.setLocalProperty(
      ContinuousExecution.EPOCH_COORDINATOR_ID_KEY, epochCoordinatorId)
    sparkSessionForQuery.sparkContext.setLocalProperty(
      ContinuousExecution.EPOCH_INTERVAL_KEY,
      trigger.asInstanceOf[ContinuousTrigger].intervalMs.toString)

    // Use the parent Spark session for the endpoint since it's where this query ID is registered.
    val epochEndpoint =
      EpochCoordinatorRef.create(
        writer, reader, this, epochCoordinatorId, currentBatchId, sparkSession, SparkEnv.get)
    val epochUpdateThread = new Thread(new Runnable {
      override def run: Unit = {
        try {
          triggerExecutor.execute(() => {
            startTrigger()

            if (reader.needsReconfiguration() && state.compareAndSet(ACTIVE, RECONFIGURING)) {
              if (queryExecutionThread.isAlive) {
                queryExecutionThread.interrupt()
              }
              false
            } else if (isActive) {
              currentBatchId = epochEndpoint.askSync[Long](IncrementAndGetEpoch)
              logInfo(s"New epoch $currentBatchId is starting.")
              true
            } else {
              false
            }
          })
        } catch {
          case _: InterruptedException =>
            // Cleanly stop the query.
            return
        }
      }
    }, s"epoch update thread for $prettyIdString")

    try {
      epochUpdateThread.setDaemon(true)
      epochUpdateThread.start()

      reportTimeTaken("runContinuous") {
        SQLExecution.withNewExecutionId(sparkSessionForQuery, lastExecution) {
          lastExecution.executedPlan.execute()
        }
      }
    } catch {
      case t: Throwable
          if StreamExecution.isInterruptionException(t) && state.get() == RECONFIGURING =>
        logInfo(s"Query $id ignoring exception from reconfiguring: $t")
        // interrupted by reconfiguration - swallow exception so we can restart the query
    } finally {
      // The above execution may finish before getting interrupted, for example, a Spark job having
      // 0 partitions will complete immediately. Then the interrupted status will sneak here.
      //
      // To handle this case, we do the two things here:
      //
      // 1. Clean up the resources in `queryExecutionThread.runUninterruptibly`. This may increase
      //    the waiting time of `stop` but should be minor because the operations here are very fast
      //    (just sending an RPC message in the same process and stopping a very simple thread).
      // 2. Clear the interrupted status at the end so that it won't impact the `runContinuous`
      //    call. We may clear the interrupted status set by `stop`, but it doesn't affect the query
      //    termination because `runActivatedStream` will check `state` and exit accordingly.
      queryExecutionThread.runUninterruptibly {
        try {
          epochEndpoint.askSync[Unit](StopContinuousExecutionWrites)
        } finally {
          SparkEnv.get.rpcEnv.stop(epochEndpoint)
          epochUpdateThread.interrupt()
          epochUpdateThread.join()
          stopSources()
          // The following line must be the last line because it may fail if SparkContext is stopped
          sparkSession.sparkContext.cancelJobGroup(runId.toString)
        }
      }
      Thread.interrupted()
    }
  }