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From Apache Wiki <wikidi...@apache.org>
Subject [Cassandra Wiki] Update of "Operations" by JonathanEllis
Date Thu, 10 Dec 2009 16:11:56 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.
http://wiki.apache.org/cassandra/Operations?action=diff&rev1=15&rev2=16

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  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`
  
- For debugging purposes you can 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. If you are seeing a lot of tasks being
built up, your hardware or configuration tuning is probably the bottleneck.
+ 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. 
+ 
+ If you are seeing a lot of tasks being built up, your hardware or configuration tuning is
probably the bottleneck.
  
  Running `nodeprobe tpstats` will dump all of those threads to console if you don't want
to use jconsole. Example:
  

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