Cassandra 3.0 latency statistic incorrect

问题:

I have setup new Cassandra 3.3 cluster. Then I use jvisualvm to monitor Cassandra read/write latency by using MBean (jmx metric).

The result of read/write latency is always stable in all nodes for many weeks whereas read/write request in that cluster have normally movement (heavy or less in some day).

As I use jvisualvm to monitor Cassandra 2.0 cluster. The read/write latency have normally behavior. It have movement depending on read/wire requests.

I wonder that Why the read/write latency statistics of Cassandra 3.0+ are always stable? And I think it is incorrect result. (I have load tested in Cassandra v3.3, v3.7).

[Updated] I have found bug relate with this issue.

Cassandra metric flat. https://issues.apache.org/jira/browse/CASSANDRA-11752

The detail show that this problem has been solved in C* version 2.2.8, 3.0.9, 3.8. But after I have tested in version 3.0.9, The result of latency still show flat line.

Any Idea?

Thanks.

回答1:

have not found any metrics problem When using C*3.3

first,try to monitor with jconsole,have met same issue？

second,which attribute do you see?avg value or percentage?there value always count from node up,so it is common to see percentage value is same.but not always happens on average value.try to restart cassandra node and check the value.