Following map reduce logs can be changed to DEBUG log level as they appear too many times in the log file and are not that important for debugging.
1. In org.apache.hadoop.mapreduce.task.reduce.Fetcher#copyFromHost(Fetcher.java : 313), the second log is not required to be at info level. This can be moved to debug as a warn log is anyways printed if verifyReply fails.
SecureShuffleUtils.verifyReply(replyHash, encHash, shuffleSecretKey);
LOG.info("for url="" sent hash and received reply");
2. Thread related info need not be printed in logs at INFO level. Below 2 logs can be moved to DEBUG
a) In org.apache.hadoop.mapreduce.task.reduce.ShuffleSchedulerImpl#getHost(ShuffleSchedulerImpl.java : 381), below log can be changed to DEBUG
LOG.info("Assigning " + host + " with " + host.getNumKnownMapOutputs() +
" to " + Thread.currentThread().getName());
b) In org.apache.hadoop.mapreduce.task.reduce.ShuffleScheduler.getMapsForHost(ShuffleSchedulerImpl.java : 411), below log can be changed to DEBUG
LOG.info("assigned " + includedMaps + " of " + totalSize + " to " +
host + " to " + Thread.currentThread().getName());