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From Dathan Pattishall <>
Subject what causes a cassandra to block and throw a null exception
Date Wed, 21 Jul 2010 03:59:06 GMT
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cassandra> connect cass01/9160
cassandra> get TimeFrameClicks.Standard2['test_cassandra_alive']
Exception null

The data exists and I can grab the data after I restart all the nodes,
but once the cluster runs for a few minutes I cannot grab this
specific key or random other keys. It takes about  3 seconds until the
Exception null message. My storage-conf.xml is very simple:

<Keyspace Name="TimeFrameClicks">
  <ColumnFamily Name="Standard2" CompareWith="UTF8Type" />

Now my data is very small like 20 GB across 4 servers. Writes
consistently remain fast, yet reads fail like crazy. I hope its
something that I am doing wrong because

nodetool cfstats

says that the read latency for the keyspace and this specific column
family is less then 0.3 ms which means that something is lying to me.

To head off some questions:

CPU utilization is very little.
There is hardly any I/O on the box
The servers are all the same class enterprise boxes
There is 12 GB of ram per server
Each Server uses a local RAID.
Nothing in any of the system logs that indicates there any problem.

Additionally is there a stat or series of stats that I can lookup to
determine the health of read performance.

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