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https://issues.apache.org/jira/browse/HADOOP-7324?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13041966#comment-13041966
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Luke Lu commented on HADOOP-7324:
---------------------------------

My limited knowledge with gmond wire format is from a quick scan of the 
GangliaContext\*.java source.

I have a question that I hope Ganglia experts can answer: the wire format seems 
_sparse_, in that it contains full key value pairs. I wonder if the update can 
be sparse as well, i.e., the metrics that haven't changed since the last 
snapshot doesn't need to be sent to gmond as well. The metrics2 system allows 
sparse update to reduce object/bandwidth usage.

If the update can be sparse, it quite straight forward to adapt FileSink and 
GangliaContext code. OTOH, If only dense update is allowed, 
{{o.a.h.metrics2.util.MetricsCache}} can be used.

> Ganglia plugins for metrics v2
> ------------------------------
>
>                 Key: HADOOP-7324
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7324
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: metrics
>    Affects Versions: 0.20.203.0, 0.23.0
>            Reporter: Luke Lu
>             Fix For: 0.20.204.0, 0.23.0
>
>
> Although, all metrics in metrics v2 are exposed via the standard JMX 
> mechanisms, there are a few users who prefer using Ganglia to collect metrics.

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