Hi Walter, Thanks for taking this up.
You can file a PR for the documentation change too as our docs are now a part of the repo. Here's where you can find the docs: https://github.com/apache/lucene-solr/tree/master/solr/solr-ref-guide On Fri, Dec 18, 2020 at 9:26 AM Walter Underwood <wun...@wunderwood.org> wrote: > Looking at the code, the CPU circuit breaker is unusable. > > This actually does use Unix load average > (operatingSystemMXBean.getSystemLoadAverage()). That is a terrible idea. > Interpreting the load average requires knowing the number of CPUs on a > system. If I have 16 CPUs, I would probably set the limit at 16, with one > process waiting for each CPU. > > Unfortunately, this implementation limits the thresholds to 0.5 to 0.95, > because the implementer thought they were getting a CPU usage value, I > guess. So the whole thing doesn’t work right. > > I’ll file a bug and submit a patch to use > OperatingSystemMXBean.getSystemCPULoad(). How do I fix the documentation? > > wunder > Walter Underwood > wun...@wunderwood.org > http://observer.wunderwood.org/ (my blog) > > > On Dec 16, 2020, at 10:41 AM, Walter Underwood <wun...@wunderwood.org> > wrote: > > > > In https://lucene.apache.org/solr/guide/8_7/circuit-breakers.html < > https://lucene.apache.org/solr/guide/8_7/circuit-breakers.html> > > > > URL to Wikipedia is broken, but that doesn’t matter, because that > article is about a different metric. The Unix “load average” is the length > of the run queue, the number of processes or threads waiting to run. That > can go much, much higher than 1.0. In a high load system, I’ve seen it at > 2X the number of CPUs or higher. > > > > Remove that link, it is misleading. > > > > The page should list the JMX metrics that are used for this. I’m > guessing this uses OperatingSystemMXBean.getSystemCPULoad(). That metric > goes from 0.0 to 1.0. > > > > > https://docs.oracle.com/javase/7/docs/jre/api/management/extension/com/sun/management/OperatingSystemMXBean.html > < > https://docs.oracle.com/javase/7/docs/jre/api/management/extension/com/sun/management/OperatingSystemMXBean.html > > > > > > I can see where the “load average” and “getSystemCPULoad” names cause > confusion, but this should be correct in the documents. > > > > Which metric is used for the memory threshold? My best guess is that the > percentage is calculated from the MemoryUsage object returned by > MemoryMXBean.getHeapMemoryUsage(). > > > > > https://docs.oracle.com/javase/7/docs/api/java/lang/management/MemoryMXBean.html > < > https://docs.oracle.com/javase/7/docs/api/java/lang/management/MemoryMXBean.html > > > > > https://docs.oracle.com/javase/7/docs/api/java/lang/management/MemoryUsage.html > < > https://docs.oracle.com/javase/7/docs/api/java/lang/management/MemoryUsage.html > > > > > > wunder > > Walter Underwood > > wun...@wunderwood.org <mailto:wun...@wunderwood.org> > > http://observer.wunderwood.org/ (my blog) > > > > -- Anshum Gupta
