I came across a similar issue today and was able to fix it. The issue was due to having "$HADOOP_CONF_DIR" as part of my Yarn classpath.  
 In my indexes.conf file, my Yarn classpath was set to this: 
  vix.yarn.application.classpath = $HADOOP_CONF_DIR,/usr/hdp/current/hadoop-client/*,/usr/hdp/current/hadoop-client/lib/*,/usr/hdp/current/hadoop-hdfs-client/*,/usr/hdp/current/hadoop-hdfs-client/lib/*,/usr/hdp/current/hadoop-yarn-client/*,/usr/hdp/current/hadoop-yarn-client/lib/*,/usr/hdp/current/hadoop-mapreduce-client/*
  
 Since $HADOOP_CONF_DIR is set to "/etc/hadoop/conf", I updated the Yarn classpath to this: 
  vix.yarn.application.classpath = /etc/hadoop/conf/*,/usr/hdp/current/hadoop-client/*,/usr/hdp/current/hadoop-client/lib/*,/usr/hdp/current/hadoop-hdfs-client/*,/usr/hdp/current/hadoop-hdfs-client/lib/*,/usr/hdp/current/hadoop-yarn-client/*,/usr/hdp/current/hadoop-yarn-client/lib/*,/usr/hdp/current/hadoop-mapreduce-client/*
  
 I restarted the search head and ran another query. It completed with no errors. Hope this helps. 
						
					
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