collectd 聚合函数配置cpu聚合

参考：https://libraries.io/github/librato/collectd-librato
https://collectd.org/wiki/index.php/Plugin:Aggregation/Config

LoadPlugin aggregation
<Plugin aggregation>
  <Aggregation>
    Plugin "cpu"
    Type "cpu"

    GroupBy "Host"
    GroupBy "TypeInstance"

    CalculateNum true
    CalculateSum true
    CalculateAverage true
  </Aggregation>
</Plugin>

LoadPlugin match_regex
<Chain "PostCache">
  <Rule "ignore_cpu"> # Send "cpu" values to the aggregation plugin
    <Match "regex">
      Plugin "^cpu$"
    </Match>
    <Target "write">
      Plugin "aggregation"
    </Target>
    Target stop
  </Rule>
  Target "write"
</Chain>