Github user mingyukim commented on a diff in the pull request:
https://github.com/apache/spark/pull/8763#discussion_r39552025
--- Diff: core/src/main/scala/org/apache/spark/rdd/NewHadoopRDD.scala ---
@@ -230,12 +251,16 @@ class NewHadoopRDD[K, V](
super.persist(storageLevel)
}
-
- def getConf: Configuration = confBroadcast.value.value
}
private[spark] object NewHadoopRDD {
/**
+ * Configuration's constructor is not threadsafe (see SPARK-1097 and
HADOOP-10456).
+ * Therefore, we synchronize on this lock before calling new
Configuration().
+ */
+ val CONFIGURATION_INSTANTIATION_LOCK = new Object()
--- End diff --
HADOOP-10456 is fixed in Hadoop 2.4.1
(https://issues.apache.org/jira/browse/HADOOP-10456), so people will still hit
the issue in some configurations.
The concurrency issue with the Configuration/JobConf instantiations seems
to be per object, not per class. (i.e. happens when two threads try to copy the
same conf object, not when two threads try to instantiate Configuration/JobConf
with two separate conf objects.) The lock could've even be allocated per
NewHadoopRDD instance or HadoopRDD instance.
So, I think this should be safe, although I can certainly move this to
SparkHadoopUtil for clarity. Please let me know what you think!
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