A null context which has a thread calling
periodically when monitoring is started. This keeps the data sampled
In all other respects, this is like the NULL context: No data is emitted.
This is suitable for Monitoring systems like JMX which reads the metrics
when someone reads the data from JMX.
The default impl of start and stop monitoring:
is the AbstractMetricsContext is good enough.
Fields inherited from interface org.apache.hadoop.metrics.MetricsContext