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From Aleksey Yeschenko <alek...@apache.org>
Subject Re: Counter values become under-counted when running repair.
Date Thu, 24 Mar 2016 18:02:19 GMT
After repair is over, does the value settle? What CLs do you write to your counters with? What
CLs are you reading with?

-- 
AY

On 24 March 2016 at 06:17:27, Dikang Gu (dikang85@gmail.com) wrote:

Hello there,  

We are experimenting Counters in Cassandra 2.2.5. Our setup is that we have  
6 nodes, across three different regions, and in each region, the  
replication factor is 2. Basically, each nodes holds a full copy of the  
data.  

When are doing 30k/s counter increment/decrement per node, and at the  
meanwhile, we are double writing to our mysql tier, so that we can measure  
the accuracy of C* counter, compared to mysql.  

The experiment result was great at the beginning, the counter value in C*  
and mysql are very close. The difference is less than 0.1%.  

But when we start to run the repair on one node, the counter value in C*  
become much less than the value in mysql, the difference becomes larger  
than 1%.  

My question is that is it a known problem that the counter value will  
become under-counted if repair is running? Should we avoid running repair  
for counter tables?  

Thanks.  

--  
Dikang  

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