Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/2684#discussion_r18498021
--- Diff: core/src/main/scala/org/apache/spark/rdd/HadoopRDD.scala ---
@@ -132,24 +132,12 @@ class HadoopRDD[K, V](
// Returns a JobConf that will be used on slaves to obtain input splits
for Hadoop reads.
protected def getJobConf(): JobConf = {
val conf: Configuration = broadcastedConf.value.value
- if (conf.isInstanceOf[JobConf]) {
- // A user-broadcasted JobConf was provided to the HadoopRDD, so
always use it.
- conf.asInstanceOf[JobConf]
- } else if (HadoopRDD.containsCachedMetadata(jobConfCacheKey)) {
- // getJobConf() has been called previously, so there is already a
local cache of the JobConf
- // needed by this RDD.
- HadoopRDD.getCachedMetadata(jobConfCacheKey).asInstanceOf[JobConf]
- } else {
- // Create a JobConf that will be cached and used across this RDD's
getJobConf() calls in the
- // local process. The local cache is accessed through
HadoopRDD.putCachedMetadata().
- // The caching helps minimize GC, since a JobConf can contain ~10KB
of temporary objects.
- // Synchronize to prevent ConcurrentModificationException
(Spark-1097, Hadoop-10456).
- HadoopRDD.CONFIGURATION_INSTANTIATION_LOCK.synchronized {
- val newJobConf = new JobConf(conf)
+ HadoopRDD.CONFIGURATION_INSTANTIATION_LOCK.synchronized {
+ val newJobConf = new JobConf(conf)
--- End diff --
JobConf seems to implement this constructor by calling the superclass's
constructor.
Take a look at the `git blame` for Configuration:
https://github.com/apache/hadoop/blame/release-2.5.1/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java#L662
It looks like this constructor performs proper copying and has done so for
a while (since 2009 or 2010).
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