[jira] [Commented] (SOLR-18284) Fix load-average and memory circuit breakers

["Jason Gerlowski (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-18284?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18129173#comment-18129173 ] 

Jason Gerlowski commented on SOLR-18284:
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Hey [~markrmiller] - should this be closed?

> Fix load-average and memory circuit breakers
> --------------------------------------------
>
>                 Key: SOLR-18284
>                 URL: https://issues.apache.org/jira/browse/SOLR-18284
>             Project: Solr
>          Issue Type: Bug
>            Reporter: Mark Robert Miller
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 6h 20m
>  Remaining Estimate: 0h
>
> Load-average and memory circuit breakers were doing more harm than good under high concurrency.
> LoadAverageCircuitBreaker called OperatingSystemMXBean.getSystemLoadAverage() on every request. The OS load average is a one-minute moving average, so re-polling it per-request is wasted work - and when many requests arrived concurrently, the syscall stampede hammered the CPU, which is the condition this breaker exists to prevent rather than cause.
> MemoryCircuitBreaker sampled MemoryMXBean.getHeapMemoryUsage().getUsed() on a 30-second moving average. With a generational collector that signal climbs toward max between collections during normal operation; the breaker would trip on transient pre-GC peaks that GC was about to reclaim.
> * I extracted these from the experimental circuit breaker overhaul PR.



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