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https://issues.apache.org/jira/browse/CASSANDRA-18454?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17869906#comment-17869906
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Brad Schoening commented on CASSANDRA-18454:
--------------------------------------------
We have a managed service environment where ops can run nodetool, and users can
run CQLSH, and neither can login to the Linux nodes. Having it available to
both certainly makes sense.
Runtime stats is a good idea.
> Enhance nodetool gcstats
> -------------------------
>
> Key: CASSANDRA-18454
> URL: https://issues.apache.org/jira/browse/CASSANDRA-18454
> Project: Cassandra
> Issue Type: Improvement
> Components: Tool/nodetool
> Reporter: Brad Schoening
> Assignee: Dhanush Ananthkar
> Priority: Normal
>
> Nodetool gcstats provides only a brief one line output of historical GC
> activity with Max, Total, Stdev, etc
> {noformat}
> % nodetool gcstats
> Interval (ms) Max GC Elapsed (ms)Total GC Elapsed (ms)Stdev GC Elapsed
> (ms) GC Reclaimed (MB) Collections Direct Memory Bytes
> 11979 0 0
> NaN 0 0 -1
> {noformat}
> 1. Performance of garbage collection is such an key part of Cassandra
> performance that it would be helpful to have more complete metrics with
> *gcstats* here. The MBean java.lang.GarbageCollector has recent statistic
> which could be added in events/second for:
> * GcThreadCount
> * Duration
> The current size of eden / survivor / old space and humongous allocations
> should be shown as well.
> The metrics show with jhsdb jmap would be very helpful as well, if they're
> available.
> [https://docs.oracle.com/en/java/javase/11/troubleshoot/diagnostic-tools.html#GUID-A69901EC-F87D-4B63-A8B7-DE8684AD4FF9]
> 2. Since physical memory is also a critical part of GC performance, it would
> be useful to report the following MBeans
> |[cassandra_os_free_memory_bytes|https://github.com/instaclustr/cassandra-exporter/wiki/Exported-Metrics#_cassandra_os_free_memory_bytes]|Amount
> of free physical memory available (as seen by the Cassandra JVM process).|
> |[cassandra_os_free_swap_bytes|https://github.com/instaclustr/cassandra-exporter/wiki/Exported-Metrics#_cassandra_os_free_swap_bytes]|Amount
> of free swap space available (as seen by the Cassandra JVM process).|
> |[cassandra_os_memory_bytes_total|https://github.com/instaclustr/cassandra-exporter/wiki/Exported-Metrics#_cassandra_os_memory_bytes_total]|Total
> physical memory available (as seen by the Cassandra JVM process).|
> |[cassandra_os_swap_bytes_total|https://github.com/instaclustr/cassandra-exporter/wiki/Exported-Metrics#_cassandra_os_swap_bytes_total]|Total
> swap space available (as seen by the Cassandra JVM process).|
> or use
> [/proc/meminfo|https://stackoverflow.com/questions/59581597/get-available-ram-in-java]
> SystemInfo.java already reads /proc/<pid>/limits on Linux systems.
> 3. Status of memlock
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