HADOOP-13921. Remove log4j classes from JobConf.

Signed-off-by: Akira Ajisaka <aajisaka@apache.org>

hadoop-client-modules/hadoop-client-runtime/pom.xml

@@ -96,7 +96,6 @@
     </dependency>
     <!-- Move log4j to optional, since it is needed for some pieces folks might not use:
          * one of the three custom log4j appenders we have
-         * JobConf (?!) (so essentially any user of MapReduce)
       -->
     <dependency>
       <groupId>log4j</groupId>

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-common/src/main/java/org/apache/hadoop/mapreduce/v2/util/MRApps.java

@@ -650,12 +650,12 @@ public class MRApps extends Apps {
     if (isMap) {
       return conf.get(
           MRJobConfig.MAP_LOG_LEVEL,
-          JobConf.DEFAULT_LOG_LEVEL.toString()
+          JobConf.DEFAULT_LOG_LEVEL
       );
     } else {
       return conf.get(
           MRJobConfig.REDUCE_LOG_LEVEL,
-          JobConf.DEFAULT_LOG_LEVEL.toString()
+          JobConf.DEFAULT_LOG_LEVEL
       );
     }
   }

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/JobConf.java

@@ -53,7 +53,6 @@ import org.apache.hadoop.security.Credentials;
 import org.apache.hadoop.util.ClassUtil;
 import org.apache.hadoop.util.ReflectionUtils;
 import org.apache.hadoop.util.Tool;
-import org.apache.log4j.Level;
 
 /** 
  * A map/reduce job configuration.
@@ -333,7 +332,7 @@ public class JobConf extends Configuration {
   private Credentials credentials = new Credentials();
   
   /**
-   * Configuration key to set the logging {@link Level} for the map task.
+   * Configuration key to set the logging level for the map task.
    *
    * The allowed logging levels are:
    * OFF, FATAL, ERROR, WARN, INFO, DEBUG, TRACE and ALL.
@@ -342,7 +341,7 @@ public class JobConf extends Configuration {
     JobContext.MAP_LOG_LEVEL;
   
   /**
-   * Configuration key to set the logging {@link Level} for the reduce task.
+   * Configuration key to set the logging level for the reduce task.
    *
    * The allowed logging levels are:
    * OFF, FATAL, ERROR, WARN, INFO, DEBUG, TRACE and ALL.
@@ -353,7 +352,7 @@ public class JobConf extends Configuration {
   /**
    * Default logging level for map/reduce tasks.
    */
-  public static final Level DEFAULT_LOG_LEVEL = Level.INFO;
+  public static final String DEFAULT_LOG_LEVEL = JobContext.DEFAULT_LOG_LEVEL;
 
   /**
    * The variable is kept for M/R 1.x applications, M/R 2.x applications should