Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/12612#discussion_r61658910
--- Diff: core/src/main/scala/org/apache/spark/NewAccumulator.scala ---
@@ -0,0 +1,391 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark
+
+import java.{lang => jl}
+import java.io.ObjectInputStream
+import java.util.concurrent.atomic.AtomicLong
+import javax.annotation.concurrent.GuardedBy
+
+import org.apache.spark.scheduler.AccumulableInfo
+import org.apache.spark.util.Utils
+
+
+private[spark] case class AccumulatorMetadata(
+ id: Long,
+ name: Option[String],
+ countFailedValues: Boolean) extends Serializable
+
+
+/**
+ * The base class for accumulators, that can accumulate inputs of type
`IN`, and produce output of
+ * type `OUT`.
+ */
+abstract class NewAccumulator[IN, OUT] extends Serializable {
+ private[spark] var metadata: AccumulatorMetadata = _
+ private[this] var atDriverSide = true
+
+ private[spark] def register(
+ sc: SparkContext,
+ name: Option[String] = None,
+ countFailedValues: Boolean = false): Unit = {
+ if (this.metadata != null) {
+ throw new IllegalStateException("Cannot register an Accumulator
twice.")
+ }
+ this.metadata = AccumulatorMetadata(AccumulatorContext.newId(), name,
countFailedValues)
+ AccumulatorContext.register(this)
+ sc.cleaner.foreach(_.registerAccumulatorForCleanup(this))
+ }
+
+ /**
+ * Returns true if this accumulator has been registered. Note that all
accumulators must be
+ * registered before ues, or it will throw exception.
+ */
+ final def isRegistered: Boolean =
+ metadata != null &&
AccumulatorContext.originals.containsKey(metadata.id)
+
+ private def assertMetadataNotNull(): Unit = {
+ if (metadata == null) {
+ throw new IllegalAccessError("The metadata of this accumulator has
not been assigned yet.")
+ }
+ }
+
+ /**
+ * Returns the id of this accumulator, can only be called after
registration.
+ */
+ final def id: Long = {
+ assertMetadataNotNull()
+ metadata.id
+ }
+
+ /**
+ * Returns the name of this accumulator, can only be called after
registration.
+ */
+ final def name: Option[String] = {
+ assertMetadataNotNull()
+ metadata.name
+ }
+
+ /**
+ * Whether to accumulate values from failed tasks. This is set to true
for system and time
+ * metrics like serialization time or bytes spilled, and false for
things with absolute values
+ * like number of input rows. This should be used for internal metrics
only.
+ */
+ private[spark] final def countFailedValues: Boolean = {
+ assertMetadataNotNull()
+ metadata.countFailedValues
+ }
+
+ /**
+ * Creates an [[AccumulableInfo]] representation of this
[[NewAccumulator]] with the provided
+ * values.
+ */
+ private[spark] def toInfo(update: Option[Any], value: Option[Any]):
AccumulableInfo = {
+ val isInternal =
name.exists(_.startsWith(InternalAccumulator.METRICS_PREFIX))
+ new AccumulableInfo(id, name, update, value, isInternal,
countFailedValues)
+ }
+
+ final private[spark] def isAtDriverSide: Boolean = atDriverSide
+
+ /**
+ * Tells if this accumulator is zero value or not. e.g. for a counter
accumulator, 0 is zero
+ * value; for a list accumulator, Nil is zero value.
+ */
+ def isZero(): Boolean
+
+ /**
+ * Creates a new copy of this accumulator, which is zero value. i.e.
call `isZero` on the copy
+ * must return true.
+ */
+ def copyAndReset(): NewAccumulator[IN, OUT]
+
+ /**
+ * Takes the inputs and accumulates. e.g. it can be a simple `+=` for
counter accumulator.
+ */
+ def add(v: IN): Unit
+
+ /**
+ * Merges another same-type accumulator into this one and update its
state, i.e. this should be
+ * merge-in-place.
+ */
+ def merge(other: NewAccumulator[IN, OUT]): Unit
+
+ /**
+ * Access this accumulator's current value; only allowed on driver.
+ */
+ final def value: OUT = {
+ if (atDriverSide) {
+ localValue
+ } else {
+ throw new UnsupportedOperationException("Can't read accumulator
value in task")
+ }
+ }
+
+ /**
+ * Defines the current value of this accumulator.
+ *
+ * This is NOT the global value of the accumulator. To get the global
value after a
+ * completed operation on the dataset, call `value`.
+ */
+ def localValue: OUT
+
+ // Called by Java when serializing an object
+ final protected def writeReplace(): Any = {
+ if (atDriverSide) {
+ if (!isRegistered) {
+ throw new UnsupportedOperationException(
+ "Accumulator must be registered before send to executor")
+ }
+ val copy = copyAndReset()
+ assert(copy.isZero(), "copyAndReset must return a zero value copy")
+ copy.metadata = metadata
+ copy
+ } else {
+ this
+ }
+ }
+
+ // Called by Java when deserializing an object
+ private def readObject(in: ObjectInputStream): Unit =
Utils.tryOrIOException {
+ in.defaultReadObject()
+ if (atDriverSide) {
+ atDriverSide = false
+
+ // Automatically register the accumulator when it is deserialized
with the task closure.
+ // This is for external accumulators and internal ones that do not
represent task level
+ // metrics, e.g. internal SQL metrics, which are per-operator.
+ val taskContext = TaskContext.get()
+ if (taskContext != null) {
+ taskContext.registerAccumulator(this)
+ }
+ } else {
+ atDriverSide = true
--- End diff --
When the accumulator is sent back from executor to driver, we should set
the `atDriverSide` flag.
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