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https://issues.apache.org/jira/browse/SOLR-15056?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jan Høydahl updated SOLR-15056:
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    Component/s: Circuit Breakers

> CPU circuit breaker needs to use CPU utilization, not Unix load average
> -----------------------------------------------------------------------
>
>                 Key: SOLR-15056
>                 URL: https://issues.apache.org/jira/browse/SOLR-15056
>             Project: Solr
>          Issue Type: Bug
>          Components: Circuit Breakers, metrics
>    Affects Versions: 8.7
>            Reporter: Walter Underwood
>            Assignee: Atri Sharma
>            Priority: Major
>              Labels: Metrics
>         Attachments: 
> 0001-SOLR-15056-Circuit-Breakers-use-CPU-utilization-inst.patch, 
> 0002-SOLR-15056-clean-up-linkage-to-SolrCore-add-back-loa.patch, 
> SOLR-15056.patch
>
>          Time Spent: 7h 10m
>  Remaining Estimate: 0h
>
> The config range, 50% to 95%, assumes that the circuit breaker is triggered 
> by a CPU utilization metric that goes from 0% to 100%. But the code uses the 
> metric OperatingSystemMXBean.getSystemLoadAverage(). That is an average of 
> the count of processes waiting to run. It is effectively unbounded. I've seen 
> it as high as 50 to 100. It is not bound by 1.0 (100%).
> A good limit for load average would need to be aware of the number of CPUs 
> available to the JVM. A load average of 8 is no problem for a 32 CPU host. It 
> is a critical situation for a 2 CPU host.
> Also, load average is a Unix OS metric. I don't know if it is even available 
> on Windows.
> Instead, use a CPU utilization metric that goes from 0.0 to 1.0. A good 
> choice is OperatingSystemMXBean.getSystemCPULoad(). This name also uses 
> "load", but it is a usage metric.
> From the Javadoc:
> > Returns the "recent cpu usage" for the whole system. This value is a double 
> >in the [0.0,1.0] interval. A value of 0.0 means that all CPUs were idle 
> >during the recent period of time observed, while a value of 1.0 means that 
> >all CPUs were actively running 100% of the time during the recent period 
> >being observed. All values betweens 0.0 and 1.0 are possible depending of 
> >the activities going on in the system. If the system recent cpu usage is not 
> >available, the method returns a negative value.
> https://docs.oracle.com/javase/7/docs/jre/api/management/extension/com/sun/management/OperatingSystemMXBean.html#getSystemCpuLoad()
> Also update the documentation to explain which JMX metrics are used for the 
> memory and CPU circuit breakers.
>  



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