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From aaron morton <>
Subject Re: CompletedTasks attribute exposed via JMX
Date Tue, 11 Oct 2011 20:55:05 GMT
Its the number of mutations, a mutation is a collection of changes for a single row across
one or more column families. 

Take a look at the nodetool cfstats, this is where I assume Ops Centre is getting it's data

Aaron Morton
Freelance Cassandra Developer

On 12/10/2011, at 3:44 AM, Alexandru Dan Sicoe wrote:

> Hello everyone,
>  I was trying to get some cluster wide statistics of the total insertions performed in
my 3 node Cassandra 0.8.6 cluster. So I wrote a nice little program that gets the CompletedTasks
attribute of org.apache.cassandra.db:type=Commitlog from every node, sums up the values and
records them in a .csv every 10 sec or so. Everything works and I get my stats but later I
found out that I am not really sure what this measure means. I think it is the individual
column insertions performed! Am I correct?
>  In the meantime I installed the trial version of the DataStax Operations Center. The
cluster wide dashboard, showing Writes performed as a function of time, gives me much smaller
values of the rates, compared to the measurement I described before. The Datastax writes/sec
are of the same order of magnitude as the batch writes I perform on the cluster. But somehow
I cannot relate between this rate and the rate of my CompletedTasks measurement.
> How do people usually measure insertion rates for their custers ? Per batch, per single
columns or is actual data rate more important to know?
> Cheers,
> Alexandru

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