[SPARK-1866] Closure cleaner does not null shadowed fields when outer scope is referenced

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Incomplete
• Affects Version/s: 1.0.0
• Component/s: Spark Core
• Labels: bulk-closed
• Assignee: Unassigned
• Reporter: Aaron Davidson
• Created: 17/May/14 03:13
• Updated: 21/May/19 04:13
• Resolved: 21/May/19 04:13

Description

Take the following example:

val x = 5
val instances = new org.apache.hadoop.fs.Path("/") /* non-serializable */
sc.parallelize(0 until 10).map { _ =>
  val instances = 3
  (instances, x)
}.collect

This produces a "java.io.NotSerializableException: org.apache.hadoop.fs.Path", despite the fact that the outer instances is not actually used within the closure. If you change the name of the outer variable instances to something else, the code executes correctly, indicating that it is the fact that the two variables share a name that causes the issue.

Additionally, if the outer scope is not used (i.e., we do not reference "x" in the above example), the issue does not appear.