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From aaron morton <>
Subject Re: Update of column sometimes takes 10 seconds
Date Mon, 26 Sep 2011 21:27:38 GMT
Try turning up the logging to DEBUG and watch the requests come through. 

Check that the two inserts do indeed have different time stamps. 

In cases of lost updates, timestamps are most often the cause of the kerfuffle.

btw, in this situation the commit log is a red hearing riding a scapegoat. Data is dumped
into the commit log for durability at the start of the write request, but it is never read
from there. Data is read from memtables and sstables. 

Aaron Morton
Freelance Cassandra Developer

On 27/09/2011, at 9:27 AM, Rick Whitesel (rwhitese) wrote:

> Thank you to all for the quick response. The test that fails is doing a insert, another
insert (to update data) and then a get to validate. If I make multiple copies of the same
test and execute them in succession, different copies will fail on successive runs. Each test
only has a single get, so one would assume the get in testN must be causing testN+1 to fail.
 It is going to take me a little bit to dig down deep enough into our code to see if that
is the issue.
> -Rick
> From: Jonathan Ellis [] 
> Sent: Monday, September 26, 2011 3:34 PM
> To:
> Subject: Re: Update of column sometimes takes 10 seconds
> Sounds a lot like this to me:
> On Mon, Sep 26, 2011 at 1:55 PM, Rick Whitesel (rwhitese) <>
> Hi All:
> We have a simple junit test that inserts a column, immediately updates that column and
then validates that the data updated. Cassandra is run embedded in the unit test. Sometimes
the test will pass, i.e. the updated data is correct, and sometimes the test will fail. The
configuration is set to:
> <CommitLogSync>periodic</CommitLogSync> and <CommitLogSyncPeriodInMS>10000</CommitLogSyncPeriodInMS>
> We are running version 0.6.9. We plan to update to the latest version but cannot until
after the release we are wrapping up. We are using the client batch mutate to create and update
the data. From what I understand, the commit log write will return immediately and the data
will be store in memory. If that is the case, then why would our test sometimes fail?
> -Rick Whitesel
> Simplify, Standardize and Conserve
> <image001.gif>
> Rick Whitesel
> Technical Lead
> Customer Contact Business Unit
> Phone :978-936-0479
> 500 Beaver Brook Road
> Boxboro, MA 01719
> Mailing address:
> 1414 Massachusetts Avenue
> Boxboro, MA 01719
> United States
> -- 
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of DataStax, the source for professional Cassandra support

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