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From aaron morton <aa...@thelastpickle.com>
Subject Re: Compaction, truncate, cqlsh problems
Date Thu, 11 Apr 2013 20:08:10 GMT
> Can you please elaborate on the specials of truncate?
I think ed was talking about this config setting in 1.2
https://github.com/apache/cassandra/blob/trunk/conf/cassandra.yaml#L484


> It works, only sometimes it silently fails (1 in 400 runs of the truncate, actually).

The data is left in place ? 
Are you making the calls very quickly? If you add a pause does it help ? 


> At the same time the truncate fails I see system ks compaction. Additionally, it seems
there is quite a lot of these system ks compactions (the numbers in the filenames go up pretty
fast to thousands).
In 1.2 truncate updates a system table, which always flush after updates. 

Cheers
-----------------
Aaron Morton
Freelance Cassandra Consultant
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 12/04/2013, at 3:12 AM, Ondřej Černoš <cernoso@gmail.com> wrote:

> Hi,
> 
> I have JNA (cassandra only complains about obsolete version - Obsolete version of JNA
present; unable to read errno. Upgrade to JNA 3.2.7 or later - I have stock centos version
3.2.4).
> 
> Usage of separate CFs for each test run is difficult to set up.
> 
> Can you please elaborate on the specials of truncate?
> 
> regards,
> Ondřej Černoš
> 
> 
> 
> On Thu, Apr 11, 2013 at 5:04 PM, Edward Capriolo <edlinuxguru@gmail.com> wrote:
> If you do not have JNA truncate has to fork an 'ln -s'' command for the snapshots. I
think that makes it un-predicatable. Truncate has its own timeout value now (separate from
the other timeouts). If possible I think it is better to make each test use it's own CF and
avoid truncate entirely.
> 
> 
> On Thu, Apr 11, 2013 at 9:48 AM, Ondřej Černoš <cernoso@gmail.com> wrote:
> Hi,
> 
> I use C* 1.2.3 and CQL3.
> 
> I integrated cassandra into our testing environment. In order to make the tests repeatable
I truncate all the tables that need to be empty before the test run via ssh session to the
host cassandra runs on and by running cqlsh where I issue the truncate.
> 
> It works, only sometimes it silently fails (1 in 400 runs of the truncate, actually).
> 
> At the same time the truncate fails I see system ks compaction. Additionally, it seems
there is quite a lot of these system ks compactions (the numbers in the filenames go up pretty
fast to thousands).
> 
> I googled truncate and found out there were some issues with race conditions and with
slowing down if truncate is used frequently (as is my case, where truncate is run before each
test in quite a big test suite).
> 
> Any hints?
> 
> Regards,
> Ondřej Černoš
> 
> 


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