Just curious - why did you restart the Data Nodes? Did they crash? ... View more

Hi @Joshua Adeleke, how frequently do you see the errors. These are some times seen in busy clusters and usually clients/HDFS recover from transient failures. If there are no job or task failures around the time you of the errors, I would just ignore them. Edit: I took a look at your attached log file. There's a lot of GC pauses as @Namit Maheshwari pointed out. Try increasing the DataNode heap size and PermGen/NewGen allocations until the GC pauses go away. 2017-03-25 10:10:18,219 WARN util.JvmPauseMonitor (JvmPauseMonitor.java:run(192)) - Detected pause in JVM or host machine (eg GC): pause of approximately 44122ms GC pool 'ConcurrentMarkSweep' had collection(s): count=1 time=44419ms ... View more

Hi @Kumar Veerappan, Yes this alert seems to be new for Ambari 2.2.2. I don't see it in the 2.2.1 release. ... View more

@apappu is correct. These JVM options should be added to HADOOP_DATANODE_OPTS in the hadoop-env template. After making the changes you should restart all the DataNodes (there is no need to restart the NameNodes). I recommend restarting DataNodes two at a time. ... View more

This error has nothing to do with the missing user-specific group. The NameNode has no requirement that the group name match the user name. As long as the id command succeeded and returned any groups the NameNode would not have logged the error. This error was likely due to a temporary infrastructure issue as pointed out by @Smart Solutions in a later comment. The following article is a good starting point for any issues related to groups lookups. https://community.hortonworks.com/articles/38591/hadoop-and-ldap-usage-load-patterns-and-tuning.html ... View more