For what it is worth, generally I would recommend just using the mean vs calculating it yourself. It's a lot easier and averages are meaningless for anything besides trending anyway (which is really what this is useful for, finding issues on the larger scale), especially with high volume clusters so the loss in accuracy kinda moot. Your average for local reads/writes will almost always be sub millisecond but you might end up having 500 millisecond requests or worse that the mean will hide.
Chris On Thu, May 30, 2019 at 6:30 AM shalom sagges <shalomsag...@gmail.com> wrote: > Thanks for your replies guys. I really appreciate it. > > @Alain, I use Graphite for backend on top of Grafana. But the goal is to > move from Graphite to Prometheus eventually. > > I tried to find a direct way of getting a specific Latency metric in > average and as Chris pointed out, then Mean value isn't that accurate. > I do not wish to use the percentile metrics either, but a single latency > metric like the *"Local read latency" *output in nodetool tablestats. > Looking at the code of nodetool tablestats, it seems that C* also divides > *ReadTotalLatency.Count* with *ReadLatency.Count *to get the latency > result. > > So I guess I will have no choice but to run the calculation on my own via > Graphite: > > divideSeries(averageSeries(keepLastValue(nonNegativeDerivative($env.path.to.host.$host.org_apache_cassandra_metrics.Table.$ks.$cf.ReadTotalLatency.Count))),averageSeries(keepLastValue(nonNegativeDerivative($env.path.to.host.$host.org_apache_cassandra_metrics.Table.$ks.$cf.ReadLatency.Count)))) > > Does this seem right to you? > > Thanks! > > On Thu, May 30, 2019 at 12:34 AM Paul Chandler <p...@redshots.com> wrote: > >> There are various attributes under >> org.apache.cassandra.metrics.ClientRequest.Latency.Read these measure the >> latency in milliseconds >> >> Thanks >> >> Paul >> www.redshots.com >> >> > On 29 May 2019, at 15:31, shalom sagges <shalomsag...@gmail.com> wrote: >> > >> > Hi All, >> > >> > I'm creating a dashboard that should collect read/write latency metrics >> on C* 3.x. >> > In older versions (e.g. 2.0) I used to divide the total read latency in >> microseconds with the read count. >> > >> > Is there a metric attribute that shows read/write latency without the >> need to do the math, such as in nodetool tablestats "Local read latency" >> output? >> > I saw there's a Mean attribute in >> org.apache.cassandra.metrics.ReadLatency but I'm not sure this is the right >> one. >> > >> > I'd really appreciate your help on this one. >> > Thanks! >> > >> > >> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: user-unsubscr...@cassandra.apache.org >> For additional commands, e-mail: user-h...@cassandra.apache.org >> >>
