Ming Ma created HDFS-5693:
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Summary: Few NN metrics data points were collected via JMX when NN
is under heavy load
Key: HDFS-5693
URL: https://issues.apache.org/jira/browse/HDFS-5693
Project: Hadoop HDFS
Issue Type: Improvement
Components: namenode
Reporter: Ming Ma
JMX sometimes doesn’t return any value when NN is under heavy load. However,
that is when we would like to get metrics to help to diagnosis the issue.
When NN is under heavy load due to bad application or other reasons, it holds
FSNamesystem's writer lock for a long period of time. Many of the FSNamesystem
metrics require FSNamesystem's reader lock and thus can't be processed.
This is a special case to improve the overall NN concurrency.
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