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/*
* 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.util
import java.io.{ByteArrayInputStream, ByteArrayOutputStream}
import java.lang.invoke.SerializedLambda
import scala.collection.mutable.{Map, Set, Stack}
import scala.language.existentials
import org.apache.xbean.asm6.{ClassReader, ClassVisitor, MethodVisitor, Type}
import org.apache.xbean.asm6.Opcodes._
import org.apache.spark.{SparkEnv, SparkException}
import org.apache.spark.internal.Logging
/**
* A cleaner that renders closures serializable if they can be done so safely.
*/
private[spark] object ClosureCleaner extends Logging {
private val isScala2_11 = scala.util.Properties.versionString.contains("2.11")
// Get an ASM class reader for a given class from the JAR that loaded it
private[util] def getClassReader(cls: Class[_]): ClassReader = {
// Copy data over, before delegating to ClassReader - else we can run out of open file handles.
val className = cls.getName.replaceFirst("^.*\\.", "") + ".class"
val resourceStream = cls.getResourceAsStream(className)
if (resourceStream == null) {
null
} else {
val baos = new ByteArrayOutputStream(128)
Utils.copyStream(resourceStream, baos, true)
new ClassReader(new ByteArrayInputStream(baos.toByteArray))
}
}
// Check whether a class represents a Scala closure
private def isClosure(cls: Class[_]): Boolean = {
cls.getName.contains("$anonfun$")
}
// Get a list of the outer objects and their classes of a given closure object, obj;
// the outer objects are defined as any closures that obj is nested within, plus
// possibly the class that the outermost closure is in, if any. We stop searching
// for outer objects beyond that because cloning the user's object is probably
// not a good idea (whereas we can clone closure objects just fine since we
// understand how all their fields are used).
private def getOuterClassesAndObjects(obj: AnyRef): (List[Class[_]], List[AnyRef]) = {
for (f <- obj.getClass.getDeclaredFields if f.getName == "$outer") {
f.setAccessible(true)
val outer = f.get(obj)
// The outer pointer may be null if we have cleaned this closure before
if (outer != null) {
if (isClosure(f.getType)) {
val recurRet = getOuterClassesAndObjects(outer)
return (f.getType :: recurRet._1, outer :: recurRet._2)
} else {
return (f.getType :: Nil, outer :: Nil) // Stop at the first $outer that is not a closure
}
}
}
(Nil, Nil)
}
/**
* Return a list of classes that represent closures enclosed in the given closure object.
*/
private def getInnerClosureClasses(obj: AnyRef): List[Class[_]] = {
val seen = Set[Class[_]](obj.getClass)
val stack = Stack[Class[_]](obj.getClass)
while (!stack.isEmpty) {
val cr = getClassReader(stack.pop())
if (cr != null) {
val set = Set.empty[Class[_]]
cr.accept(new InnerClosureFinder(set), 0)
for (cls <- set -- seen) {
seen += cls
stack.push(cls)
}
}
}
(seen - obj.getClass).toList
}
/** Initializes the accessed fields for outer classes and their super classes. */
private def initAccessedFields(
accessedFields: Map[Class[_], Set[String]],
outerClasses: Seq[Class[_]]): Unit = {
for (cls <- outerClasses) {
var currentClass = cls
assert(currentClass != null, "The outer class can't be null.")
while (currentClass != null) {
accessedFields(currentClass) = Set.empty[String]
currentClass = currentClass.getSuperclass()
}
}
}
/** Sets accessed fields for given class in clone object based on given object. */
private def setAccessedFields(
outerClass: Class[_],
clone: AnyRef,
obj: AnyRef,
accessedFields: Map[Class[_], Set[String]]): Unit = {
for (fieldName <- accessedFields(outerClass)) {
val field = outerClass.getDeclaredField(fieldName)
field.setAccessible(true)
val value = field.get(obj)
field.set(clone, value)
}
}
/** Clones a given object and sets accessed fields in cloned object. */
private def cloneAndSetFields(
parent: AnyRef,
obj: AnyRef,
outerClass: Class[_],
accessedFields: Map[Class[_], Set[String]]): AnyRef = {
val clone = instantiateClass(outerClass, parent)
var currentClass = outerClass
assert(currentClass != null, "The outer class can't be null.")
while (currentClass != null) {
setAccessedFields(currentClass, clone, obj, accessedFields)
currentClass = currentClass.getSuperclass()
}
clone
}
/**
* Clean the given closure in place.
*
* More specifically, this renders the given closure serializable as long as it does not
* explicitly reference unserializable objects.
*
* @param closure the closure to clean
* @param checkSerializable whether to verify that the closure is serializable after cleaning
* @param cleanTransitively whether to clean enclosing closures transitively
*/
def clean(
closure: AnyRef,
checkSerializable: Boolean = true,
cleanTransitively: Boolean = true): Unit = {
clean(closure, checkSerializable, cleanTransitively, Map.empty)
}
/**
* Try to get a serialized Lambda from the closure.
*
* @param closure the closure to check.
*/
private def getSerializedLambda(closure: AnyRef): Option[SerializedLambda] = {
if (isScala2_11) {
return None
}
val isClosureCandidate =
closure.getClass.isSynthetic &&
closure
.getClass
.getInterfaces.exists(_.getName == "scala.Serializable")
if (isClosureCandidate) {
try {
Option(inspect(closure))
} catch {
case e: Exception =>
// no need to check if debug is enabled here the Spark
// logging api covers this.
logDebug("Closure is not a serialized lambda.", e)
None
}
} else {
None
}
}
private def inspect(closure: AnyRef): SerializedLambda = {
val writeReplace = closure.getClass.getDeclaredMethod("writeReplace")
writeReplace.setAccessible(true)
writeReplace.invoke(closure).asInstanceOf[java.lang.invoke.SerializedLambda]
}
/**
* Helper method to clean the given closure in place.
*
* The mechanism is to traverse the hierarchy of enclosing closures and null out any
* references along the way that are not actually used by the starting closure, but are
* nevertheless included in the compiled anonymous classes. Note that it is unsafe to
* simply mutate the enclosing closures in place, as other code paths may depend on them.
* Instead, we clone each enclosing closure and set the parent pointers accordingly.
*
* By default, closures are cleaned transitively. This means we detect whether enclosing
* objects are actually referenced by the starting one, either directly or transitively,
* and, if not, sever these closures from the hierarchy. In other words, in addition to
* nulling out unused field references, we also null out any parent pointers that refer
* to enclosing objects not actually needed by the starting closure. We determine
* transitivity by tracing through the tree of all methods ultimately invoked by the
* inner closure and record all the fields referenced in the process.
*
* For instance, transitive cleaning is necessary in the following scenario:
*
* class SomethingNotSerializable {
* def someValue = 1
* def scope(name: String)(body: => Unit) = body
* def someMethod(): Unit = scope("one") {
* def x = someValue
* def y = 2
* scope("two") { println(y + 1) }
* }
* }
*
* In this example, scope "two" is not serializable because it references scope "one", which
* references SomethingNotSerializable. Note that, however, the body of scope "two" does not
* actually depend on SomethingNotSerializable. This means we can safely null out the parent
* pointer of a cloned scope "one" and set it the parent of scope "two", such that scope "two"
* no longer references SomethingNotSerializable transitively.
*
* @param func the starting closure to clean
* @param checkSerializable whether to verify that the closure is serializable after cleaning
* @param cleanTransitively whether to clean enclosing closures transitively
* @param accessedFields a map from a class to a set of its fields that are accessed by
* the starting closure
*/
private def clean(
func: AnyRef,
checkSerializable: Boolean,
cleanTransitively: Boolean,
accessedFields: Map[Class[_], Set[String]]): Unit = {
// most likely to be the case with 2.12, 2.13
// so we check first
// non LMF-closures should be less frequent from now on
val lambdaFunc = getSerializedLambda(func)
if (!isClosure(func.getClass) && lambdaFunc.isEmpty) {
logDebug(s"Expected a closure; got ${func.getClass.getName}")
return
}
// TODO: clean all inner closures first. This requires us to find the inner objects.
// TODO: cache outerClasses / innerClasses / accessedFields
if (func == null) {
return
}
if (lambdaFunc.isEmpty) {
logDebug(s"+++ Cleaning closure $func (${func.getClass.getName}) +++")
// A list of classes that represents closures enclosed in the given one
val innerClasses = getInnerClosureClasses(func)
// A list of enclosing objects and their respective classes, from innermost to outermost
// An outer object at a given index is of type outer class at the same index
val (outerClasses, outerObjects) = getOuterClassesAndObjects(func)
// For logging purposes only
val declaredFields = func.getClass.getDeclaredFields
val declaredMethods = func.getClass.getDeclaredMethods
if (log.isDebugEnabled) {
logDebug(s" + declared fields: ${declaredFields.size}")
declaredFields.foreach { f => logDebug(s" $f") }
logDebug(s" + declared methods: ${declaredMethods.size}")
declaredMethods.foreach { m => logDebug(s" $m") }
logDebug(s" + inner classes: ${innerClasses.size}")
innerClasses.foreach { c => logDebug(s" ${c.getName}") }
logDebug(s" + outer classes: ${outerClasses.size}" )
outerClasses.foreach { c => logDebug(s" ${c.getName}") }
logDebug(s" + outer objects: ${outerObjects.size}")
outerObjects.foreach { o => logDebug(s" $o") }
}
// Fail fast if we detect return statements in closures
getClassReader(func.getClass).accept(new ReturnStatementFinder(), 0)
// If accessed fields is not populated yet, we assume that
// the closure we are trying to clean is the starting one
if (accessedFields.isEmpty) {
logDebug(" + populating accessed fields because this is the starting closure")
// Initialize accessed fields with the outer classes first
// This step is needed to associate the fields to the correct classes later
initAccessedFields(accessedFields, outerClasses)
// Populate accessed fields by visiting all fields and methods accessed by this and
// all of its inner closures. If transitive cleaning is enabled, this may recursively
// visits methods that belong to other classes in search of transitively referenced fields.
for (cls <- func.getClass :: innerClasses) {
getClassReader(cls).accept(new FieldAccessFinder(accessedFields, cleanTransitively), 0)
}
}
logDebug(s" + fields accessed by starting closure: " + accessedFields.size)
accessedFields.foreach { f => logDebug(" " + f) }
// List of outer (class, object) pairs, ordered from outermost to innermost
// Note that all outer objects but the outermost one (first one in this list) must be closures
var outerPairs: List[(Class[_], AnyRef)] = outerClasses.zip(outerObjects).reverse
var parent: AnyRef = null
if (outerPairs.nonEmpty) {
val (outermostClass, outermostObject) = outerPairs.head
if (isClosure(outermostClass)) {
logDebug(s" + outermost object is a closure, so we clone it: ${outerPairs.head}")
} else if (outermostClass.getName.startsWith("$line")) {
// SPARK-14558: if the outermost object is a REPL line object, we should clone
// and clean it as it may carray a lot of unnecessary information,
// e.g. hadoop conf, spark conf, etc.
logDebug(s" + outermost object is a REPL line object, so we clone it: ${outerPairs.head}")
} else {
// The closure is ultimately nested inside a class; keep the object of that
// class without cloning it since we don't want to clone the user's objects.
// Note that we still need to keep around the outermost object itself because
// we need it to clone its child closure later (see below).
logDebug(" + outermost object is not a closure or REPL line object," +
"so do not clone it: " + outerPairs.head)
parent = outermostObject // e.g. SparkContext
outerPairs = outerPairs.tail
}
} else {
logDebug(" + there are no enclosing objects!")
}
// Clone the closure objects themselves, nulling out any fields that are not
// used in the closure we're working on or any of its inner closures.
for ((cls, obj) <- outerPairs) {
logDebug(s" + cloning the object $obj of class ${cls.getName}")
// We null out these unused references by cloning each object and then filling in all
// required fields from the original object. We need the parent here because the Java
// language specification requires the first constructor parameter of any closure to be
// its enclosing object.
val clone = cloneAndSetFields(parent, obj, cls, accessedFields)
// If transitive cleaning is enabled, we recursively clean any enclosing closure using
// the already populated accessed fields map of the starting closure
if (cleanTransitively && isClosure(clone.getClass)) {
logDebug(s" + cleaning cloned closure $clone recursively (${cls.getName})")
// No need to check serializable here for the outer closures because we're
// only interested in the serializability of the starting closure
clean(clone, checkSerializable = false, cleanTransitively, accessedFields)
}
parent = clone
}
// Update the parent pointer ($outer) of this closure
if (parent != null) {
val field = func.getClass.getDeclaredField("$outer")
field.setAccessible(true)
// If the starting closure doesn't actually need our enclosing object, then just null it out
if (accessedFields.contains(func.getClass) &&
!accessedFields(func.getClass).contains("$outer")) {
logDebug(s" + the starting closure doesn't actually need $parent, so we null it out")
field.set(func, null)
} else {
// Update this closure's parent pointer to point to our enclosing object,
// which could either be a cloned closure or the original user object
field.set(func, parent)
}
}
logDebug(s" +++ closure $func (${func.getClass.getName}) is now cleaned +++")
} else {
logDebug(s"Cleaning lambda: ${lambdaFunc.get.getImplMethodName}")
// scalastyle:off classforname
val captClass = Class.forName(lambdaFunc.get.getCapturingClass.replace('/', '.'),
false, Thread.currentThread.getContextClassLoader)
// scalastyle:on classforname
// Fail fast if we detect return statements in closures
getClassReader(captClass)
.accept(new ReturnStatementFinder(Some(lambdaFunc.get.getImplMethodName)), 0)
logDebug(s" +++ Lambda closure (${lambdaFunc.get.getImplMethodName}) is now cleaned +++")
}
if (checkSerializable) {
ensureSerializable(func)
}
}
private def ensureSerializable(func: AnyRef) {
try {
if (SparkEnv.get != null) {
SparkEnv.get.closureSerializer.newInstance().serialize(func)
}
} catch {
case ex: Exception => throw new SparkException("Task not serializable", ex)
}
}
private def instantiateClass(
cls: Class[_],
enclosingObject: AnyRef): AnyRef = {
// Use reflection to instantiate object without calling constructor
val rf = sun.reflect.ReflectionFactory.getReflectionFactory()
val parentCtor = classOf[java.lang.Object].getDeclaredConstructor()
val newCtor = rf.newConstructorForSerialization(cls, parentCtor)
val obj = newCtor.newInstance().asInstanceOf[AnyRef]
if (enclosingObject != null) {
val field = cls.getDeclaredField("$outer")
field.setAccessible(true)
field.set(obj, enclosingObject)
}
obj
}
}
private[spark] class ReturnStatementInClosureException
extends SparkException("Return statements aren't allowed in Spark closures")
private class ReturnStatementFinder(targetMethodName: Option[String] = None)
extends ClassVisitor(ASM6) {
override def visitMethod(access: Int, name: String, desc: String,
sig: String, exceptions: Array[String]): MethodVisitor = {
// $anonfun$ covers Java 8 lambdas
if (name.contains("apply") || name.contains("$anonfun$")) {
// A method with suffix "$adapted" will be generated in cases like
// { _:Int => return; Seq()} but not { _:Int => return; true}
// closure passed is $anonfun$t$1$adapted while actual code resides in $anonfun$s$1
// visitor will see only $anonfun$s$1$adapted, so we remove the suffix, see
// https://github.com/scala/scala-dev/issues/109
val isTargetMethod = targetMethodName.isEmpty ||
name == targetMethodName.get || name == targetMethodName.get.stripSuffix("$adapted")
new MethodVisitor(ASM6) {
override def visitTypeInsn(op: Int, tp: String) {
if (op == NEW && tp.contains("scala/runtime/NonLocalReturnControl") && isTargetMethod) {
throw new ReturnStatementInClosureException
}
}
}
} else {
new MethodVisitor(ASM6) {}
}
}
}
/** Helper class to identify a method. */
private case class MethodIdentifier[T](cls: Class[T], name: String, desc: String)
/**
* Find the fields accessed by a given class.
*
* The resulting fields are stored in the mutable map passed in through the constructor.
* This map is assumed to have its keys already populated with the classes of interest.
*
* @param fields the mutable map that stores the fields to return
* @param findTransitively if true, find fields indirectly referenced through method calls
* @param specificMethod if not empty, visit only this specific method
* @param visitedMethods a set of visited methods to avoid cycles
*/
private[util] class FieldAccessFinder(
fields: Map[Class[_], Set[String]],
findTransitively: Boolean,
specificMethod: Option[MethodIdentifier[_]] = None,
visitedMethods: Set[MethodIdentifier[_]] = Set.empty)
extends ClassVisitor(ASM6) {
override def visitMethod(
access: Int,
name: String,
desc: String,
sig: String,
exceptions: Array[String]): MethodVisitor = {
// If we are told to visit only a certain method and this is not the one, ignore it
if (specificMethod.isDefined &&
(specificMethod.get.name != name || specificMethod.get.desc != desc)) {
return null
}
new MethodVisitor(ASM6) {
override def visitFieldInsn(op: Int, owner: String, name: String, desc: String) {
if (op == GETFIELD) {
for (cl <- fields.keys if cl.getName == owner.replace('/', '.')) {
fields(cl) += name
}
}
}
override def visitMethodInsn(
op: Int, owner: String, name: String, desc: String, itf: Boolean) {
for (cl <- fields.keys if cl.getName == owner.replace('/', '.')) {
// Check for calls a getter method for a variable in an interpreter wrapper object.
// This means that the corresponding field will be accessed, so we should save it.
if (op == INVOKEVIRTUAL && owner.endsWith("$iwC") && !name.endsWith("$outer")) {
fields(cl) += name
}
// Optionally visit other methods to find fields that are transitively referenced
if (findTransitively) {
val m = MethodIdentifier(cl, name, desc)
if (!visitedMethods.contains(m)) {
// Keep track of visited methods to avoid potential infinite cycles
visitedMethods += m
var currentClass = cl
assert(currentClass != null, "The outer class can't be null.")
while (currentClass != null) {
ClosureCleaner.getClassReader(currentClass).accept(
new FieldAccessFinder(fields, findTransitively, Some(m), visitedMethods), 0)
currentClass = currentClass.getSuperclass()
}
}
}
}
}
}
}
}
private class InnerClosureFinder(output: Set[Class[_]]) extends ClassVisitor(ASM6) {
var myName: String = null
// TODO: Recursively find inner closures that we indirectly reference, e.g.
// val closure1 = () = { () => 1 }
// val closure2 = () => { (1 to 5).map(closure1) }
// The second closure technically has two inner closures, but this finder only finds one
override def visit(version: Int, access: Int, name: String, sig: String,
superName: String, interfaces: Array[String]) {
myName = name
}
override def visitMethod(access: Int, name: String, desc: String,
sig: String, exceptions: Array[String]): MethodVisitor = {
new MethodVisitor(ASM6) {
override def visitMethodInsn(
op: Int, owner: String, name: String, desc: String, itf: Boolean) {
val argTypes = Type.getArgumentTypes(desc)
if (op == INVOKESPECIAL && name == "" && argTypes.length > 0
&& argTypes(0).toString.startsWith("L") // is it an object?
&& argTypes(0).getInternalName == myName) {
// scalastyle:off classforname
output += Class.forName(
owner.replace('/', '.'),
false,
Thread.currentThread.getContextClassLoader)
// scalastyle:on classforname
}
}
}
}
}
