I've been advising users to truncate the table by removing entries older than 1 or 2 months. The DB is used to support search in Ranger UI, and the events are independent, so, IMO, no harm is done. They are also storing audit data in hdfs as well, and all data remains available there if needed. When you truncate the table by date, you can use the event_time field, for example in case of Mysql delete from xa_access_audit where event_time < DATE_SUB(now(), INTERVAL 1 MONTH); ... View more

You haven't cleared Ambari DB. Stop ambari-server and do this ambari-server reset # answer yes to all prompts dropdb -U ambari ambari # default PW is "bigdata" ambari-server setup # continue with Ambari install ... View more

Q1) Why only two Nodes have all the Mapper tasks running. Why are the other nodes not running any mapper? A: Mappers and reducers only run in Yarn containers on nodes running Node Manager. Click on your Yarn service in Ambari, and in the Summary tab check how many NMs do you have. You most likely have only 2 NMs on Machine1 and Machine2. Now, why only 2 mappers per machine? That depends on your Yarn and MapReduce settings. If no other jobs are running it means each node can run only 2 mappers at a time. To confirm check your yarn.nodemanager.resource.memory-mb in Yarn, and mapreduce.map.memory.mb in Mapreduce. Q2) If one mapper is per 128 MB file block, why the mapper task on machine 1 is showing 21627027 byes (21120 MB) of data ? A: 21627027 bytes is 21,627,027 or about 21M, not 21120M and so less than 128M. Note also that all blocks are not 128M, some are smaller (if a file has 150M one block will be "full" 128M, another one will be only 22M). ... View more