http://www.datastax.com/support-forums/topic/write-latency-is-shown-as-nan Software, Support, and Training for Apache Cassandra en-US Sun, 19 May 2013 06:36:45 +0000 http://bbpress.org/?v=1.0.3 q http://www.datastax.com/support-forums/search.php http://www.datastax.com/support-forums/topic/write-latency-is-shown-as-nan#post-7539 Fri, 16 Nov 2012 22:23:08 +0000 thobbs 7539@http://www.datastax.com/support-forums/ <blockquote><p>Is there any way to get overall read/write latency for a column family?</p></blockquote> <p>You will have to go through JMX (e.g. use jconsole), but you can get the Read/WriteCount value and the TotalRead/WriteLatencyMicros value from the column family MBean and divide the second by the first.</p> <blockquote><p>What about latency values shown at keyspace level - are they for all transactions since cassandra started?</p></blockquote> <p>Yes, they are for all transactions since Cassandra started. Nodetool basically does what I describe above. </p> http://www.datastax.com/support-forums/topic/write-latency-is-shown-as-nan#post-7538 Fri, 16 Nov 2012 21:15:14 +0000 ravi.videla 7538@http://www.datastax.com/support-forums/ <p>Thanks Thobbs. Is there any way to get overall read/write latency for a column family? What about latency values shown at keyspace level - are they for all transactions since cassandra started? </p> http://www.datastax.com/support-forums/topic/write-latency-is-shown-as-nan#post-7533 Fri, 16 Nov 2012 19:38:15 +0000 thobbs 7533@http://www.datastax.com/support-forums/ <p>The write latency measured there is the "recent" write latency, which only covers writes since the last time the latency value was checked (basically, the last time nodetool cfstats was run or something like OpsCenter checked the value). If there haven't been any new writes since the last time it was checked, you will see NaN. </p> http://www.datastax.com/support-forums/topic/write-latency-is-shown-as-nan#post-7532 Fri, 16 Nov 2012 18:51:48 +0000 ravi.videla 7532@http://www.datastax.com/support-forums/ <p>Hi,</p> <p>We are using Apache Cassandra 1.0.5. For some column families, write latency is shown as NaN even though write count is present. See below. How can i make it show correct latency value. Appreciate your help.</p> <p>Keyspace: Test1<br /> Read Count: 389056<br /> Read Latency: 0.03497599831386741 ms.<br /> Write Count: 43413<br /> Write Latency: 0.024415106074217402 ms.<br /> Pending Tasks: 0<br /> Column Family: test_cf<br /> SSTable count: 2<br /> Space used (live): 1007557<br /> Space used (total): 1007557<br /> Number of Keys (estimate): 1408<br /> Memtable Columns Count: 54<br /> Memtable Data Size: 27125<br /> Memtable Switch Count: 20<br /> Read Count: 389056<br /> Read Latency: 0.104 ms.<br /> Write Count: 43413<br /> Write Latency: NaN ms.<br /> Pending Tasks: 0<br /> Bloom Filter False Postives: 0<br /> Bloom Filter False Ratio: 0.00000<br /> Bloom Filter Space Used: 2344<br /> Key cache capacity: 200000<br /> Key cache size: 802<br /> Key cache hit rate: 1.0<br /> Row cache: disabled<br /> Compacted row minimum size: 643<br /> Compacted row maximum size: 924<br /> Compacted row mean size: 847 </p>