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https://issues.apache.org/jira/browse/CASSANDRA-11432?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15255297#comment-15255297
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Aleksey Yeschenko commented on CASSANDRA-11432:
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bq. Yes, we do see large amount of time out during repair.
What is you policy for handling timeouts for counters? Do you ignore or do you
retry? It seems like you are undercounting because you you either don't retry
timed out increments, or do retry decrements. That's about it, and is expected
- there is no way around it.
bq. If repair is not running, the difference is very small, only 10s.
Explained by exactly the same reason - you do time out sometimes, just a lot
less than when running repair.
The question then becomes 'why are we seeing a lot more timeouts when repair is
running'.
> 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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