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From Apache Wiki <wikidi...@apache.org>
Subject [Cassandra Wiki] Update of "Operations" by JonathanEllis
Date Tue, 07 Sep 2010 03:27:29 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Cassandra Wiki" for change notification.

The "Operations" page has been changed by JonathanEllis.
The comment on this change is: link jconsole-via-ssh post.
http://wiki.apache.org/cassandra/Operations?action=diff&rev1=67&rev2=68

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  Running `nodetool cfstats` can provide an overview of each Column Family, and important
metrics to graph your cluster. Some folks prefer having to deal with non-jmx clients, there
is a JMX-to-REST bridge available at http://code.google.com/p/polarrose-jmx-rest-bridge/
  
- Important metrics to watch on a per-Column Family basis would be: '''Read Count, Read Latency,
Write Count and Write Latency'''. '''Pending Tasks''' tell you if things are backing up. These
metrics can also be exposed using any JMX client such as `jconsole`
+ Important metrics to watch on a per-Column Family basis would be: '''Read Count, Read Latency,
Write Count and Write Latency'''. '''Pending Tasks''' tell you if things are backing up. These
metrics can also be exposed using any JMX client such as `jconsole`.  (See also [[http://simplygenius.com/2010/08/jconsole-via-socks-ssh-tunnel.html]]
for how to proxy JConsole to firewalled machines.)
  
  You can also use jconsole, and the MBeans tab to look at PendingTasks for thread pools.
If you see one particular thread backing up, this can give you an indication of a problem.
One example would be ROW-MUTATION-STAGE indicating that write requests are arriving faster
than they can be handled. A more subtle example is the FLUSH stages: if these start backing
up, cassandra is accepting writes into memory fast enough, but the sort-and-write-to-disk
stages are falling behind.
  

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