Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/3518#discussion_r21062519
--- Diff:
core/src/main/scala/org/apache/spark/util/SerializationHelper.scala ---
@@ -0,0 +1,127 @@
+/*
+ * 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.
+ */
+
+// Created by Ilya Ganelin
+package org.apache.spark.util
+
+import java.io.NotSerializableException
+
+import org.apache.spark.rdd.RDD
+import org.apache.spark.scheduler.Task
+import org.apache.spark.serializer.{SerializerInstance, Serializer}
+
+import scala.collection.mutable.HashMap
+import scala.util.control.NonFatal
+
+/**
+ * This class is designed to encapsulate some utilities to facilitate
debugging serialization
+ * problems in the DAGScheduler and the TaskSetManager. See SPARK-3694.
+ */
+object SerializationHelper {
+ // Define vars to standardize debugging output
+ var Failed = "Failed to serialize"
+ var FailedDeps = "Failed to serialize dependencies"
+ var Serialized = "Serialized"
+
+ /**
+ * Helper function to check whether an RDD is serializable.
+ *
+ * If any dependency of an RDD is un-serializable, a
NotSerializableException will be thrown
+ * and the entire RDD will be deemed un-serializable if done with a
single try-catch.
+ *
+ * Therefore, split the evaluation into two stages, in the first stage
attempt to serialize
+ * the rdd. If it fails, attempt to serialize its dependencies in the
failure handler and see
+ * if those also fail.
+ *
+ * This approach will show if any of the dependencies are
un-serializable and will not
+ * incorrectly identify the parent RDD as being serializable.
+ *
+ * @param closureSerializer - An instance of a serializer
(single-threaded) that will be used
+ * @param rdd - Rdd to attempt to serialize
+ * @return - An output string qualifying success or failure.
+ */
+ def isSerializable(closureSerializer : SerializerInstance, rdd : RDD[_])
: String = {
--- End diff --
Maybe a better return type would be an Either: it either returns serialized
bytes or an error trace.
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