maropu commented on a change in pull request #28463:
URL: https://github.com/apache/spark/pull/28463#discussion_r422011000
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File path: core/src/main/scala/org/apache/spark/util/ClosureCleaner.scala
##########
@@ -414,6 +434,296 @@ private[spark] object ClosureCleaner extends Logging {
}
}
+private[spark] object IndylambdaScalaClosures extends Logging {
+ // internal name of java.lang.invoke.LambdaMetafactory
+ val LambdaMetafactoryClassName = "java/lang/invoke/LambdaMetafactory"
+ // the method that Scala indylambda use for bootstrap method
+ val LambdaMetafactoryMethodName = "altMetafactory"
+ val LambdaMetafactoryMethodDesc = "(Ljava/lang/invoke/MethodHandles$Lookup;"
+
+ "Ljava/lang/String;Ljava/lang/invoke/MethodType;[Ljava/lang/Object;)" +
+ "Ljava/lang/invoke/CallSite;"
+
+ /**
+ * Check if the given reference is a indylambda style Scala closure.
+ * If so, return a non-empty serialization proxy (SerializedLambda) of the
closure;
+ * otherwise return None.
+ *
+ * @param maybeClosure the closure to check.
+ */
+ def getSerializationProxy(maybeClosure: AnyRef): Option[SerializedLambda] = {
+ val maybeClosureClass = maybeClosure.getClass
+
+ // shortcut the fast check:
+ // 1. indylambda closure classes are generated by Java's
LambdaMetafactory, and they're always
+ // synthetic.
+ // 2. We only care about Serializable closures, so let's check that as well
+ if (!maybeClosureClass.isSynthetic ||
!maybeClosure.isInstanceOf[Serializable]) return None
Review comment:
nit: How about using pattern-matching here like this;
```
def isClosureCandidate(clazz: Class[_]): Boolean = {
val implementedInterfaces = ClassUtils.getAllInterfaces(clazz).asScala
implementedInterfaces.exists(_.getName.startsWith("scala.Function"))
}
maybeClosure.getClass match {
// shortcut the fast check:
// 1. indylambda closure classes are generated by Java's
LambdaMetafactory, and they're always
// synthetic.
// 2. We only care about Serializable closures, so let's check that as
well
case c if !c.isSynthetic || !maybeClosure.isInstanceOf[Serializable]
=> None
case c if isClosureCandidate(c) =>
try {
val lambdaProxy = inspect(maybeClosure)
Option(lambdaProxy).filter(isIndylambdaScalaClosure)
} catch {
case e: Exception =>
// no need to check if debug is enabled here the Spark logging
api covers this.
logDebug("The given reference is not an indylambda Scala
closure.", e)
None
}
case _ => None
}
```
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