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From Chris Lohfink <clohf...@blackbirdit.com>
Subject Re: How often are JMX Cassandra metrics reset?
Date Thu, 28 Aug 2014 22:55:30 GMT
In the version of metrics used theres a uniform reservoir and a exponentially weighted one.
 This is used to compute the min, max, mean, std dev and quantiles.  For the timers it uses
by default it uses the exp. decaying one which is weighted for the last 5 minutes. 

http://grepcode.com/file/repo1.maven.org/maven2/com.yammer.metrics/metrics-core/2.2.0/com/yammer/metrics/core/Timer.java?av=f

Chris Lohfink


On Aug 28, 2014, at 5:39 PM, Donald Smith <Donald.Smith@audiencescience.com> wrote:

> The metrics OneMinuteRate, FIveMinuteRate, FifteenMinuteRate, and MeanRate  are NOT lifetime
values but they’re all counts of requests, not latency.  The latency values (Max, Count,
50thPercentile, Mean, etc) ARE lifetime values, I think, and thus would seem to be kinda useless
for me, since our servers have been running for months. 
>  
> Maybe there’s a way to reset lifetime metrics to zero. I connected to a cassandra server
remotely via jConsole (port 7199) and I can read various metrics via the MBeans, but I don’t
see an operation for resetting to zero.   But perhaps that’s because I’m connecting remotely.
>  
> ClientRequest/Read/Latency:
>     LatencyUnit = MICROSECONDS
>     FiveMinuteRate = 1.12
>     FifteenMinuteRate = 1.11
>     RateUnit = SECONDS
>     MeanRate = 1.65
>     OneMinuteRate = 1.13
>     EventType = calls
>    Max = 237,373.37
>     Count = 961,312
>     50thPercentile = 383.2
>     Mean = 908.46
>     Min = 95.64
>     StdDev = 3,034.62
>     75thPercentile = 626.34
>     95thPercentile = 954.31
>     98thPercentile = 1,443.11
>     99thPercentile = 1,472.4
>     999thPercentile = 1,858.1
>  
>  
> From: Nick Bailey [mailto:nick@datastax.com] 
> Sent: Thursday, August 28, 2014 1:50 PM
> To: user@cassandra.apache.org
> Subject: Re: How often are JMX Cassandra metrics reset?
>  
> Those percentile values should be for the lifetime of the node yes. Depending on what
version of OpsCenter you are using it is either using the 'recent' metrics described by Rob,
or it is using the FiveMinuteRate from JMX as well as doing some of it's own aggregation depending
on the rollup size.
>  
> 
> On Thu, Aug 28, 2014 at 12:36 PM, Robert Coli <rcoli@eventbrite.com> wrote:
> On Thu, Aug 28, 2014 at 9:27 AM, Donald Smith <Donald.Smith@audiencescience.com>
wrote:
> And yet OpsCenter shows graphs with ever-changing metrics that show recent performance.
Does OpsCenter not get its stats from JMX?
>  
> 1) Certain JMX endpoints expose "recent" metrics, or at least used to. These are "recent"
as in "since the last time someone polled this endpoint."
> 2) OpsCenter samples via JMX and then stores metrics in its own columnfamily. I would
not be shocked if it does some minor aggregation as it does so.
>  
> This all said, OpsCenter is not Apache Cassandra software, so the Apache Cassandra user
mailing list may not be the ideal place for it to be discussed or supported...
>  
> =Rob


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