HDFS-9009. Send metrics logs to NullAppender by default. (Arpit Agarwal)

hadoop-common-project/hadoop-common/src/main/conf/log4j.properties

@@ -152,7 +152,8 @@ log4j.appender.RFAAUDIT.MaxBackupIndex=${hdfs.audit.log.maxbackupindex}
 # NameNode metrics logging.
 # The default is to retain two namenode-metrics.log files up to 64MB each.
 #
-log4j.logger.NameNodeMetricsLog=INFO,NNMETRICSRFA
+namenode.metrics.logger=INFO,NullAppender
+log4j.logger.NameNodeMetricsLog=${namenode.metrics.logger}
 log4j.additivity.NameNodeMetricsLog=false
 log4j.appender.NNMETRICSRFA=org.apache.log4j.RollingFileAppender
 log4j.appender.NNMETRICSRFA.File=${hadoop.log.dir}/namenode-metrics.log

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -1287,6 +1287,8 @@ Release 2.8.0 - UNRELEASED
     HDFS-8885. ByteRangeInputStream used in webhdfs does not override
     available(). (Shradha Revankar via aajisaka)
 
+    HDFS-9009. Send metrics logs to NullAppender by default. (Arpit Agarwal)
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES