SPARK-1480: Clean up use of classloaders

The Spark codebase is a bit fast-and-loose when accessing classloaders and this has caused a few bugs to surface in master.

This patch defines some utility methods for accessing classloaders. This makes the intention when accessing a classloader much more explicit in the code and fixes a few cases where the wrong one was chosen.

case (a) -> We want the classloader that loaded Spark
case (b) -> We want the context class loader, or if not present, we want (a)

This patch provides a better fix for SPARK-1403 (https://issues.apache.org/jira/browse/SPARK-1403) than the current work around, which it reverts. It also fixes a previously unreported bug that the `./spark-submit` script did not work for running with `local` master. It didn't work because the executor classloader did not properly delegate to the context class loader (if it is defined) and in local mode the context class loader is set by the `./spark-submit` script. A unit test is added for that case.

Author: Patrick Wendell <pwendell@gmail.com>

Closes #398 from pwendell/class-loaders and squashes the following commits:

b4a1a58 [Patrick Wendell] Minor clean up
14f1272 [Patrick Wendell] SPARK-1480: Clean up use of classloaders

1 files changed, 3 insertions, 1 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/package.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/package.scala
index a001d95359..49fc4f70fd 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/package.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/package.scala
@@ -19,6 +19,8 @@ package org.apache.spark.sql.catalyst
 
 import java.io.{PrintWriter, ByteArrayOutputStream, FileInputStream, File}
 
+import org.apache.spark.util.{Utils => SparkUtils}
+
 package object util {
   /**
    * Returns a path to a temporary file that probably does not exist.
@@ -54,7 +56,7 @@ package object util {
   def resourceToString(
       resource:String,
       encoding: String = "UTF-8",
-      classLoader: ClassLoader = this.getClass.getClassLoader) = {
+      classLoader: ClassLoader = SparkUtils.getSparkClassLoader) = {
     val inStream = classLoader.getResourceAsStream(resource)
     val outStream = new ByteArrayOutputStream
     try {