[jira] [Commented] (CASSANDRA-11432) Counter values become under-counted when running repair.

["Dikang Gu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-11432?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15216546#comment-15216546 ] 

Dikang Gu commented on CASSANDRA-11432:
---------------------------------------

We did more experiments, and we found that the counter value was still inconsistent even when the repair was finished. Seems the repair caused some permanent damage to the counters.

> Counter values become under-counted when running repair.
> --------------------------------------------------------
>
>                 Key: CASSANDRA-11432
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11432
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Dikang Gu
>            Assignee: Aleksey Yeschenko
>
> 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.
> We are writing to cluster with CL = 2, and reading with CL = 1. 
> 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. 



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