From 4b6729a76f4ef53b6bb742d7ec8be60e1bb7c640 Mon Sep 17 00:00:00 2001
From: Xingbo Jiang <xingbo.jiang@databricks.com>
Date: Thu, 29 Jun 2017 21:17:43 +0800
Subject: [PATCH] add comments

---
 .../apache/spark/scheduler/OutputCommitCoordinatorSuite.scala   | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/core/src/test/scala/org/apache/spark/scheduler/OutputCommitCoordinatorSuite.scala b/core/src/test/scala/org/apache/spark/scheduler/OutputCommitCoordinatorSuite.scala
index 82d4276a938bf..1579b614ea5b0 100644
--- a/core/src/test/scala/org/apache/spark/scheduler/OutputCommitCoordinatorSuite.scala
+++ b/core/src/test/scala/org/apache/spark/scheduler/OutputCommitCoordinatorSuite.scala
@@ -269,6 +269,8 @@ private case class OutputCommitFunctions(tempDirPath: String) {
       isAppend = false)
 
     // Create TaskAttemptContext.
+    // Hadoop wants a 32-bit task attempt ID, so if ours is bigger than Int.MaxValue, roll it
+    // around by taking a mod. We expect that no task will be attempted 2 billion times.
     val taskAttemptId = (ctx.taskAttemptId % Int.MaxValue).toInt
     val attemptId = new TaskAttemptID(
       new TaskID(jobId.value, TaskType.MAP, ctx.partitionId), taskAttemptId)