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https://issues.apache.org/jira/browse/HDDS-910?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16718804#comment-16718804
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Elek, Marton commented on HDDS-910:
-----------------------------------
Thanks [~bharatviswa] to explain it. I am not so familiar with the Ambari
metrics but it's a little bit strange for me.
As I see in the MetricsSystemImpl.register a MetricsSourceBuilder is used to
register the metrics POJO (OMMetrics in our case). It seems that the
MetricsSourceBuilder creates the required MetricsSource for the POJO:
{code}
public MetricsSource build() {
if (source instanceof MetricsSource) {
if (hasAtMetric && !hasRegistry) {
throw new MetricsException("Hybrid metrics: registry required.");
}
return (MetricsSource) source;
}
else if (!hasAtMetric) {
throw new MetricsException("No valid @Metric annotation found.");
}
return new MetricsSource() {
@Override
public void getMetrics(MetricsCollector builder, boolean all) {
registry.snapshot(builder.addRecord(registry.info()), all);
}
};
}
{code}
It's not clear why the MetricsSource should be implemented.
I also checked other metrics classes: CapacitySchedulerMetrics,
BlockReaderLocalMetrics, DataNodeMetrics, ... They don't implement the
MetricsSource interface (but my guess is that the Ambari Metric still read the
values from them somehow).
> Expose OMMetrics
> ----------------
>
> Key: HDDS-910
> URL: https://issues.apache.org/jira/browse/HDDS-910
> Project: Hadoop Distributed Data Store
> Issue Type: Bug
> Reporter: Bharat Viswanadham
> Assignee: Bharat Viswanadham
> Priority: Major
> Attachments: HDDS-910.00.patch
>
>
> Implement MetricsSource interface, so that external metrics can collect the
> OMMetrics.
>
> From *MetricsSource.java:*
> It registers with \{@link MetricsSystem}, which periodically polls it to
> collect \{@link MetricsRecord} and passes it to \{@link MetricsSink}.
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