[SPARK-15681][CORE] allow lowercase or mixed case log level string when calling sc.setLogLevel

## What changes were proposed in this pull request?
Currently `SparkContext API setLogLevel(level: String) `can not handle lower case or mixed case input string. But `org.apache.log4j.Level.toLevel` can take lowercase or mixed case.

This PR is to allow case-insensitive user input for the log level.

## How was this patch tested?
A unit testcase is added.

Author: Xin Wu <xinwu@us.ibm.com>

Closes #13422 from xwu0226/reset_loglevel.

1 files changed, 15 insertions, 0 deletions

diff --git a/core/src/test/scala/org/apache/spark/SparkContextSuite.scala b/core/src/test/scala/org/apache/spark/SparkContextSuite.scala
index ae665138b9..4fa3cab181 100644
--- a/core/src/test/scala/org/apache/spark/SparkContextSuite.scala
+++ b/core/src/test/scala/org/apache/spark/SparkContextSuite.scala
@@ -363,4 +363,19 @@ class SparkContextSuite extends SparkFunSuite with LocalSparkContext {
     sc.stop()
     assert(result == null)
   }
+
+  test("log level case-insensitive and reset log level") {
+    sc = new SparkContext(new SparkConf().setAppName("test").setMaster("local"))
+    val originalLevel = org.apache.log4j.Logger.getRootLogger().getLevel
+    try {
+      sc.setLogLevel("debug")
+      assert(org.apache.log4j.Logger.getRootLogger().getLevel === org.apache.log4j.Level.DEBUG)
+      sc.setLogLevel("INfo")
+      assert(org.apache.log4j.Logger.getRootLogger().getLevel === org.apache.log4j.Level.INFO)
+    } finally {
+      sc.setLogLevel(originalLevel.toString)
+      assert(org.apache.log4j.Logger.getRootLogger().getLevel === originalLevel)
+      sc.stop()
+    }
+  }
 }