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Aleksey Yeschenko commented on CASSANDRA-11432:
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You might be right, though I don't see it as a counters problem at this point
(and there isn't much to be done here, either, so I'll be closing the ticket).
That said, some improvements that might help here eventually:
- CASSANDRA-10862, to reduce the number of referenced sstables during reads
after streaming, will affect the read before write portion of counter writes
- CASSANDRA-9811, when implemented, will allow to eliminate some of the
sstables on the read-before-write path, if any sstable X has its highest
timestamp that is lower than the last-read global shard's for the node
> 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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