scala---SparkContet的方法集合源码理解

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accumulable:创建一个[org.apache.spark.Accumulable]共享变量。

/**
   * Create an [[org.apache.spark.Accumulable]] shared variable, to which tasks can add values
   * with `+=`. Only the driver can access the accumulable's `value`.
   * @tparam R accumulator result type
   * @tparam T type that can be added to the accumulator
   */
  @deprecated("use AccumulatorV2", "2.0.0")
  def accumulable[R, T](initialValue: R)(implicit param: AccumulableParam[R, T])
    : Accumulable[R, T] = {
    val acc = new Accumulable(initialValue, param)
    cleaner.foreach(_.registerAccumulatorForCleanup(acc.newAcc))
    acc
  }

  /**
   * Create an [[org.apache.spark.Accumulable]] shared variable, with a name for display in the
   * Spark UI. Tasks can add values to the accumulable using the `+=` operator. Only the driver can
   * access the accumulable's `value`.
   * @tparam R accumulator result type
   * @tparam T type that can be added to the accumulator
   */
  @deprecated("use AccumulatorV2", "2.0.0")
  def accumulable[R, T](initialValue: R, name: String)(implicit param: AccumulableParam[R, T])
    : Accumulable[R, T] = {
    val acc = new Accumulable(initialValue, param, Option(name))
    cleaner.foreach(_.registerAccumulatorForCleanup(acc.newAcc))
    acc
  }

  /**
   * Create an accumulator from a "mutable collection" type.
   *
   * Growable and TraversableOnce are the standard APIs that guarantee += and ++=, implemented by
   * standard mutable collections. So you can use this with mutable Map, Set, etc.
   */
  @deprecated("use AccumulatorV2", "2.0.0")
  def accumulableCollection[R <% Growable[T] with TraversableOnce[T] with Serializable: ClassTag, T]
      (initialValue: R): Accumulable[R, T] = {
    // TODO the context bound (<%) above should be replaced with simple type bound and implicit
    // conversion but is a breaking change. This should be fixed in Spark 3.x.
    val param = new GrowableAccumulableParam[R, T]
    val acc = new Accumulable(initialValue, param)
    cleaner.foreach(_.registerAccumulatorForCleanup(acc.newAcc))
    acc
  }

未完待续。。。。。