Question: Over time there might be millions of log files stored on to hdfs. How to configure auto purging logs older than x number of days?
Answer: Admins can enable auto killing indexing logs by setting druid.indexer.logs.kill.enabled to true. and configure druid.indexer.logs.kill.durationToRetain to retain task logs that were created in last x milliseconds.
Please see http://druid.io/docs/latest/configuration/indexing-service.html#task-logging for more details.