Xu Zhao created HDFS-12332:
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Summary: Logging improvement suggestion for SampleStat function
MinMax.add
Key: HDFS-12332
URL: https://issues.apache.org/jira/browse/HDFS-12332
Project: Hadoop HDFS
Issue Type: Improvement
Components: metrics
Affects Versions: 3.0.0-alpha4
Reporter: Xu Zhao
Priority: Minor
In order to debug performance anomlies, it is better to see when the max and
min value get updated in metrics.
For example, in our workload we would like to see the longest latency of a
write block request on DataNode.
The following metric updating code could possibly update the min/max value in
SampleStat class:
{code:java}
datanode.getMetrics().addWriteBlockOp(elapsed());
datanode.getMetrics().incrWritesFromClient(peer.isLocal(), size);
{code}
Here I am attaching an attempt to patch it.
The patch just adds additional DEBUG level logging in the MinMax class and
prints the new value when it gets updated.
Please let me know what you think. For example, if this patch would introduce
too much noises, what is the best way to trace the read/writeBlock that has the
minimum/maximum latency?
Any comments are appreciated!
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