load on cluster nodes

[Marcelo Elias Del Valle <mv...@gmail.com>]

Hello,

     I am writing a lot of data on a cassandra cluster with 3 nodes. All my
three nodes are seeds, when I create the astyanax connection pool I specify
ip1,ip2,ip3 as seeds and so in the casandra.yaml config file.
      However, if I look at the server load when I am bombarding it with
data, I can see the first server is clearly being more demanded (graph
here: http://mvalle.com/downloads/serverload1.png) . I am writting data in
sequence, generating UUIDs for column families based on timestamp. Also, I
am using default partitioning (cassandra 1.1.9).
      Any hint why this is happening and how to solve it? I would expect
server loads to be more equal along the cluster...

Best regards,
-- 
Marcelo Elias Del Valle
http://mvalle.com - @mvallebr

Re: load on cluster nodes

["Hiller, Dean" <De...@nrel.gov>]

Check the logs for compaction.  CPU will go up while one node may be compacting and the other node is not compacting yet.  Compaction can also last quite a long time in some cases.  Also, you can do a jstack –l {pid} > thread.txt to do a thread dump to see what that node is doing and compare it with other nodes.

I am actually in the process of doing quite a bit of performance analysis myself and I know I need to go back and tweak the astyanax client somehow as well as I found I can run a test of running jmap heap dump on node 1 in my cluster and our website sometimes slows down(ie. I keep refreshing the pages) and I feel astyanax is going back to node 1 too often which results in a 10 second page load vs. when it hits nodes that are fine, it loads in 300ms.

We have been running live for a while and get various percentage bumps on some nodes vs. others but mostly has been compaction running at different times for quite a while.

Dean

From: Marcelo Elias Del Valle <mv...@gmail.com>>
Reply-To: "user@cassandra.apache.org<ma...@cassandra.apache.org>" <us...@cassandra.apache.org>>
Date: Wednesday, February 20, 2013 3:53 PM
To: "user@cassandra.apache.org<ma...@cassandra.apache.org>" <us...@cassandra.apache.org>>
Subject: load on cluster nodes

Hello,

     I am writing a lot of data on a cassandra cluster with 3 nodes. All my three nodes are seeds, when I create the astyanax connection pool I specify ip1,ip2,ip3 as seeds and so in the casandra.yaml config file.
      However, if I look at the server load when I am bombarding it with data, I can see the first server is clearly being more demanded (graph here: http://mvalle.com/downloads/serverload1.png) . I am writting data in sequence, generating UUIDs for column families based on timestamp. Also, I am using default partitioning (cassandra 1.1.9).
      Any hint why this is happening and how to solve it? I would expect server loads to be more equal along the cluster...

Best regards,
--
Marcelo Elias Del Valle
http://mvalle.com - @mvallebr