Junegunn Choi created HBASE-29399:
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Summary: Update hadoop-metrics2-hbase.properties template
Key: HBASE-29399
URL: https://issues.apache.org/jira/browse/HBASE-29399
Project: HBase
Issue Type: Improvement
Components: conf, documentation
Reporter: Junegunn Choi
h2. Problem
The
[hadoop-metrics2-hbase.properties|https://github.com/apache/hbase/blob/master/conf/hadoop-metrics2-hbase.properties]
configuration template has a few errors, and it doesn't provide enough
examples to show how to configure the metrics.
h2. Issues and suggestions
h3. Invalid wildcard pattern
{code}
*.sink.file*.class=org.apache.hadoop.metrics2.sink.FileSink
{code}
It seems the original intention of {{file\*}} was to match all instances with
{{file}} prefix. However, it doesn't work as expected. Such partial wildcard
patterns are not allowed by [the regular
expression|https://github.com/apache/hadoop/blob/8378ab9f92c72dc6164b62f7be71826fd750dba4/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/impl/MetricsConfig.java#L88]
in the Hadoop codebase.
If we change it to {{\*.sink.\*.class}}, then it does match all instances. But
that would be overly broad and likely unintended, so I don't think we should do
that. Instead, I suggest just removing this line because it's pointless and
misleading.
h3. Incorrect context
{code}
# hbase.sink.file0.context=hmaster
{code}
The context should be {{master}}, not {{hmaster}}.
h3. Missing regionserver context example
I think it's strange that we don't show a sink example for {{regionserver}},
when we have others like thrift1, thrift2, and rest.
h3. Better naming of instances
The instances are named {{file-all}}, then {{file0}}, {{file1}}, {{file2}}, and
so on. More descriptive names like {{file-master}} or {{file-thrift1}} would
make the configuration easier to understand and maintain.
h3. Provide a filtering example
HBase emits a large number of metrics, and it is sometimes desired to reduce
the number by filtering out the metrics you are not interested in. But the
template doesn't provide a good example of how to do it.
Here is a sample configuration (we actually use) that demonstrates how to
exclude some metrics.
{code}
hbase.source.metric.filter.class=org.apache.hadoop.metrics2.filter.RegexFilter
hbase.source.metric.filter.exclude=.*_((25|75|90|95|98)th_percentile|min|mean)
{code}
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