[SPARK-5355] make SparkConf thread-safe

The SparkConf is not thread-safe, but is accessed by many threads. The getAll() could return parts of the configs if another thread is access it.

This PR changes SparkConf.settings to a thread-safe TrieMap.

Author: Davies Liu <davies@databricks.com>

Closes #4143 from davies/safe-conf and squashes the following commits:

f8fa1cf [Davies Liu] change to TrieMap
a1d769a [Davies Liu] make SparkConf thread-safe

(cherry picked from commit 9bad062268676aaa66dcbddd1e0ab7f2d7742425)
Signed-off-by: Josh Rosen <joshrosen@databricks.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/core/src/main/scala/org/apache/spark/SparkConf.scala b/core/src/main/scala/org/apache/spark/SparkConf.scala
index dae170f942..dd80013757 100644
--- a/core/src/main/scala/org/apache/spark/SparkConf.scala
+++ b/core/src/main/scala/org/apache/spark/SparkConf.scala
@@ -18,6 +18,7 @@
 package org.apache.spark
 
 import scala.collection.JavaConverters._
+import scala.collection.concurrent.TrieMap
 import scala.collection.mutable.{HashMap, LinkedHashSet}
 import org.apache.spark.serializer.KryoSerializer
 
@@ -46,7 +47,7 @@ class SparkConf(loadDefaults: Boolean) extends Cloneable with Logging {
   /** Create a SparkConf that loads defaults from system properties and the classpath */
   def this() = this(true)
 
-  private[spark] val settings = new HashMap[String, String]()
+  private[spark] val settings = new TrieMap[String, String]()
 
   if (loadDefaults) {
     // Load any spark.* system properties
@@ -177,7 +178,7 @@ class SparkConf(loadDefaults: Boolean) extends Cloneable with Logging {
   }
 
   /** Get all parameters as a list of pairs */
-  def getAll: Array[(String, String)] = settings.clone().toArray
+  def getAll: Array[(String, String)] = settings.toArray
 
   /** Get a parameter as an integer, falling back to a default if not set */
   def getInt(key: String, defaultValue: Int): Int = {