Thanks Kanaka Kumar Avvaru for the effort.
Here are some comments on the patch.
1. datanode.metrics.logger=INFO,NullAppender, I think default we can set to enable metrics logs as done for nnmetrics. I feel both should be in sync in defualt behaviour. If NullAppender is used, same is preferred for nnmetrics too.
2. I see no trim() happens for dn-metrics but done for NN. Any particular reason for this?
3. public ScheduledThreadPoolExecutor getMetricsLoggerTimer(), I think default accessor is enough. No need of public. agree?