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https://issues.apache.org/jira/browse/HADOOP-6728?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12917714#action_12917714
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Luke Lu commented on HADOOP-6728:
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Hi Eric,
Thanks for the +1 :) the main reason we decided to use metrics2 is that we
anticipated alternative evolution paths preferred by the community (see:
http://goo.gl/Rjb1 and http://goo.gl/NLLs). It looks like like old and new
metrics packages are going to coexist for a while, i.e. taking the #2 path:
* Port all hadoop core metrics (common, hdfs and mapreduce) to new framework.
* Deprecating the old metrics package so that external package (e.g. HBase
etc.) can still function (in the old way)
BTW, there is already implicit versioning in hadoop as well, e.g., mapred vs
mapreduce package, which I think is more confusing to (newer) people as it's
not immediately clear which one is the new version.
IMO, it's quite reasonable to have some package versioning scheme, when there
is a coexisting period for old and new packages that are not compatible.
> Overhaul metrics framework
> --------------------------
>
> Key: HADOOP-6728
> URL: https://issues.apache.org/jira/browse/HADOOP-6728
> Project: Hadoop Common
> Issue Type: Improvement
> Affects Versions: 0.20.2
> Reporter: Luke Lu
> Assignee: Luke Lu
> Fix For: 0.22.0
>
> Attachments: hadoop-6728-y20.104.patch, metrics1-flow.png,
> metrics2-builder-r2.png, metrics2-builder.png, metrics2-flow.png,
> metrics2-mutable-r2.png, metrics2-mutable.png, metrics2-record-r2.png,
> metrics2-record.png, metrics2-uml-r2.png, metrics2-uml.png
>
>
> Per discussions with Arun, Chris, Hong and Rajiv, et al, we concluded that
> the current metrics framework needs an overhaul to:
> * Allow multiple plugins for different monitoring systems simultaneously (see
> also: HADOOP-6508).
> * Refresh metrics plugin config without server restart.
> ** Including filtering of metrics per plugin.
> * Support metrics schema for plugins.
> The jira will be resolved when core hadoop components (hdfs, mapreduce) are
> updated to use the new framework . Updates to external components that use
> the existing metrics framework will be tracked by different issues.
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